The Big Dipper, also known as the Plough, is an asterism of seven stars recognized as a distinct grouping in many cultures. These stars are the brightest of the formal constellation Ursa Major; six of them are second magnitude stars, while only Megrez is of third magnitude. The North Star, the current northern pole star on Earth, can be located by extending an imaginary line from Merak through Dubhe. Polaris is part of the "Little Dipper", Ursa Minor.

Collinder 399 is a random grouping of stars located in the constellation Vulpecula near the border with Sagitta. Collinder 399 is known as Al Sufi's Cluster or Brocchi's Cluster. The brighter members of this star cluster form an asterism also known as the Coathanger.

The Double Cluster is the common name for the naked-eye open clusters NGC 869 and NGC 884, which are close together in the constellation Perseus. NGC 869 and NGC 884 both lie at a distance of 7500 light years. NGC 869 has a mass of 3700 solar masses and NGC 884 weighs in at 2800 solar masses; however, later research has shown both clusters are surrounded with a very extensive halo of stars, with a total mass for the complex of at least 20,000 solar masses. Based on their individual stars, the clusters are relatively young, both 12.8 million years old. In comparison, the Pleiades have an estimated age ranging from 75 million years to 150 million years. There are more than 300 blue-white super-giant stars in each of the clusters. The clusters are also blueshifted, with NGC 869 approaching Earth at a speed of 39 km/s and NGC 884 approaching at a similar speed of 38 km/s. Their hottest main sequence stars are of spectral type B0.

Kemble's Cascade, located in the constellation Camelopardalis, is an asterism — a pattern created by unrelated stars. It is an apparent straight line of more than 20 colourful 5th to 10th magnitude stars over a distance of approximately five moon diameters, and the open cluster NGC 1502 can be found at one end.
It was named by Walter Scott Houston in honour of Father Lucian Kemble, a Franciscan friar and amateur astronomer who wrote a letter to Houston about the asterism, describing it as "a beautiful cascade of faint stars tumbling from the northwest down to the open cluster NGC 1502" that he had discovered while sweeping the sky with a pair of 7×35 binoculars.
Houston was so impressed that he wrote an article on the asterism that appeared in his Deep Sky Wonders column in the astronomy magazine Sky & Telescope in 1980, in which he named it Kemble's Cascade.
Father Lucian Kemble was also associated with two other asterisms, Kemble 2 and Kemble's Kite. In addition, an asteroid, 78431 Kemble, was named in his honour.

Messier 73 is an asterism of four stars in the constellation of Aquarius. An asterism is composed of physically unconnected stars that appear close to each other in the sky as seen from Earth.

Orion's Belt or the Belt of Orion, also known as the Three Kings is an asterism in the constellation Orion. It consists of the three bright stars Alnitak, Alnilam and Mintaka.
Looking for Orion's Belt in the night sky is the easiest way to locate the constellation Orion in the sky. The stars are more or less evenly spaced in a straight line, and so can be visualized as the belt of the hunter's clothing. They are best visible in the early night sky during the Northern Winter/Southern Summer, in particular the month of January at around 9.00 pm.

The Summer Triangle is an astronomical asterism involving an imaginary triangle drawn on the northern hemisphere's celestial sphere, with its defining vertices at Altair, Deneb, and Vega, the brightest stars in the three constellations of Aquila, Cygnus, and Lyra, respectively. In the mid to late 20th century, before INS, GPS and other electronic/mechanical equipment took their places in military aircraft, USAF navigators training at Mather AFB, Rancho Cordova, California referred to this asterism as the "Navigator's Triangle".
The term was popularized by American author H.A. Rey and British astronomer Sir Patrick Moore in the 1950s. The name can be found in constellation guidebooks as far back as 1913. The Austrian astronomer Oswald Thomas described these stars as "Grosses Dreieck" in the late 1920s and "Sommerliches Dreieck" in 1934. The asterism was remarked upon by J. J. Littrow, who described it as the "conspicuous triangle" in the text of his atlas, and Bode connected the stars in a map in a book in 1816, although without label.

The Winter Hexagon or Winter Circle/Oval is an asterism appearing to be in the form of a hexagon with vertices at Rigel, Aldebaran, Capella, Pollux, Procyon, and Sirius. It is mostly upon the Northern Hemisphere's celestial sphere. On most locations on Earth, this asterism is prominently in the sky from approximately December to March. In the tropics and southern hemisphere, this can be extended with the bright star Canopus in the south.
Smaller and more regularly shaped is the Winter Triangle, an approximately equilateral triangle that shares two vertices with the larger asterism. The third vertex is Betelgeuse, which lies near the center of the hexagon. These three stars are three of the ten brightest objects, as viewed from Earth, outside the Solar System. Betelgeuse is also particularly easy to locate, being a shoulder of Orion, which assists stargazers in finding the triangle. Once the triangle is located, the larger hexagon may then be found.
Several of the stars in the hexagon may also be found independently of one another by following various lines traced through various stars in Orion.

(29075) 1950 DA is a near-Earth asteroid. Among asteroids more than 1 km in diameter, it is notable for having the highest known probability of impacting Earth. In 2002, it had the highest Palermo rating with a value of 0.17 for a possible collision in 2880. In 2013, the odds of an Earth impact in 2880 were estimated as 1 in 4,000 with a Palermo rating of −0.83. In 2014, the odds of an Earth impact were further reduced to only 1 in 20,000 with a Palermo rating of −1.81.

10 Hygiea is the fourth largest asteroid in the Solar System by volume and mass, and it is located in the asteroid belt. With somewhat oblong diameters of 350–500 km and a mass estimated to be 2.9% of the total mass of the belt, it is the largest of the class of dark C-type asteroids with a carbonaceous surface.
Despite its size, it appears very dim when observed from Earth. This is due to its dark surface and larger-than-average distance from the Sun. For this reason, several smaller asteroids were observed before Annibale de Gasparis discovered Hygiea on April 12, 1849. At most oppositions, Hygiea has a magnitude that is four magnitudes dimmer than Vesta's, and observing it will require at least a 100 millimetres telescope. However, while at a perihelic opposition, it may be observable with 10x50 binoculars.

101955 Bennu is an Apollo asteroid discovered by the LINEAR Project on September 11, 1999. It is the planned target of the OSIRIS-REx mission which is intended to return samples to Earth for further study. It is a potential Earth impactor and is listed on the Sentry Risk Table with the third highest rating on the Palermo Technical Impact Hazard Scale.
101955 Bennu has a mean diameter of approximately 493 meters and has been observed extensively with the Arecibo Observatory Planetary Radar and the Goldstone Deep Space Network.

Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered, and it is one of the largest asteroids in the Solar System. It is estimated to comprise 7% of the mass of the asteroid belt, and its diameter of 544 kilometres is slightly larger than that of 4 Vesta. It is 10–30% less massive than Vesta, placing it third among the asteroids. It is likely a remnant protoplanet.
When Pallas was discovered by astronomer Heinrich Wilhelm Matthäus Olbers on March 28, 1802, it was counted as a planet, as were other asteroids in the early 19th century. The discovery of many more asteroids after 1845 eventually led to their reclassification.
The Palladian surface appears to be a silicate material; the surface spectrum and estimated density resemble carbonaceous chondrite meteorites. The Palladian orbit, at 34.8°, is unusually highly inclined to the plane of the asteroid belt, and the orbital eccentricity is nearly as large as that of Pluto, making Pallas relatively inaccessible to spacecraft.

243 Ida is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa and named after a nymph from Greek mythology. Later telescopic observations categorized Ida as an S-type asteroid, the most numerous type in the inner asteroid belt. On 28 August 1993, Ida was visited by the spacecraft Galileo, bound for Jupiter. It was the second asteroid to be visited by a spacecraft and the first found to possess a satellite.
Like all main-belt asteroids, Ida's orbit lies between the planets Mars and Jupiter. Its orbital period is 4.84 years, and its rotation period is 4.63 hours. Ida has an average diameter of 31.4 km. It is irregularly shaped and elongated, and apparently composed of two large objects connected together. Its surface is one of the most heavily cratered in the Solar System, featuring a wide variety of crater sizes and ages.
Ida's moon, Dactyl, was discovered by mission member Ann Harch in images returned from Galileo. It was named after the Dactyls, creatures which inhabited Mount Ida in Greek mythology. Dactyl, being only 1.4 kilometres in diameter, is about one-twentieth the size of Ida.

Juno, minor-planet designation 3 Juno in the Minor Planet Center catalogue system, was the third asteroid to be discovered and is one of the larger main-belt asteroids, being one of the two largest stony asteroids, along with 15 Eunomia. It is estimated to contain 1% of the total mass of the asteroid belt. Juno was discovered on September 1, 1804, by German astronomer Karl L. Harding.

3753 Cruithne is an Aten asteroid in orbit around the Sun in 1:1 orbital resonance with Earth, making it a co-orbital object. It is a minor planet in solar orbit that, relative to Earth, orbits in a bean-shaped orbit that ultimately effectively describes a horseshoe, and which can transition into a quasi-satellite orbit. It has been incorrectly called "Earth's second moon". Cruithne does not orbit Earth and at times it is on the other side of the Sun. Its orbit takes it inside the orbit of Mercury and outside the orbit of Mars. Cruithne orbits the Sun in about 1 year but it takes 770 years for the series to complete a horseshoe-shaped movement around the Earth.
The name Cruithne is from Old Irish and refers to the early Picts in the Annals of Ulster and their eponymous king in the Pictish Chronicle. The name is cognate with "Britain" and "British".

Vesta, minor-planet designation 4 Vesta, is one of the largest asteroids in the Solar System, with a mean diameter of 525 kilometres. It was discovered by Heinrich Wilhelm Olbers on 29 March 1807 and is named after Vesta, the virgin goddess of home and hearth from Roman mythology.
Vesta is the second-most-massive asteroid after the dwarf planet Ceres, and it comprises an estimated 9% of the mass of the asteroid belt. The less-massive Pallas is slightly larger, making Vesta third in volume. Vesta is the last remaining rocky protoplanet of the kind that formed the terrestrial planets. Numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vesta's southern hemisphere. Debris from these events have fallen to Earth as howardite–eucrite–diogenite meteorites, which have been a rich source of information about Vesta.
Vesta is the brightest asteroid visible from Earth. Its maximum distance from the Sun is slightly farther than the minimum distance of Ceres from the Sun, though its orbit lies entirely within that of Ceres.

4179 Toutatis is an Apollo, Alinda, and Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with the planet Jupiter, a 1:4 resonance with the planet Earth, and frequent close approaches to the terrestrial planets, including Earth. It is listed as a potentially hazardous object, although the odds of a collision with Earth are minute.
On December 12, 2012 at 06:40 UT Toutatis passed within about 18 lunar distances of Earth. On December 13, the Chinese lunar probe Chang'e 2, launched in 2010 on a lunar mission, flew by Toutatis at a distance of 3.2 kilometers and a relative velocity of 10.73 km/s. Toutatis will approach Earth again in 2016, but will not make another notably close approach until 2069.

433 Eros is an S-type near-Earth asteroid approximately 34.4×11.2×11.2 kilometres in size, the second-largest near-Earth asteroid after 1036 Ganymed. It was discovered in 1898 and was the first near-Earth asteroid discovered. It was the first asteroid orbited by an Earth probe. It belongs to the Amor group.
Eros is a Mars-crosser asteroid, the first known to come within the orbit of Mars. Objects in such an orbit can remain there for only a few hundred million years before the orbit is perturbed by gravitational interactions. Dynamical integrations suggest that Eros may evolve into an Earth-crosser within as short an interval as two million years, and has a roughly 50% chance of doing so over a time scale of 10⁸–10⁹ years. It is a potential Earth impactor, comparable in size to the impactor that created Chicxulub crater and led to the extinction of the dinosaurs.
The NEAR Shoemaker probe visited Eros twice, first with a 1998 flyby, and then by orbiting it in 2000 when it extensively photographed its surface. On February 12, 2001, at the end of its mission, it landed on the asteroid's surface using its maneuvering jets.

90377 Sedna is a large planetoid in the outer reaches of the Solar System that was, as of 2012, about three times as far from the Sun as Neptune. Spectroscopy has revealed that Sedna's surface composition is similar to that of some other trans-Neptunian objects, being largely a mixture of water, methane and nitrogen ices with tholins. Its surface is one of the reddest among Solar System objects. It is most likely a dwarf planet.
For most of its orbit it is even farther from the Sun than at present, with its aphelion estimated at 937 astronomical units, making it one of the most distant known objects in the Solar System other than long-period comets. Sedna's exceptionally long and elongated orbit, taking approximately 11,400 years to complete, and distant point of closest approach to the Sun, at 76 AU, have led to much speculation about its origin. The Minor Planet Center currently places Sedna in the scattered disc, a group of objects sent into highly elongated orbits by the gravitational influence of Neptune.

90482 Orcus is a Kuiper belt object with a large moon, Vanth. It was discovered on February 17, 2004 by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. Precovery images as early as November 8, 1951 were later identified. It is probably a dwarf planet.
Orcus is a plutino, locked in a 2:3 resonance with Neptune, making two revolutions around the Sun to every three of Neptune's. This is much like Pluto, except that it is constrained to always be in the opposite phase of its orbit from Pluto: Orcus is at aphelion when Pluto is at perihelion and vice versa. Because of this, along with its large moon Vanth that recalls Pluto's large moon Charon, Orcus has been seen as the anti-Pluto. This was a major consideration in selecting its name, as the deity Orcus was the Etruscan equivalent of the Roman Pluto, and later became an alternate name for Pluto.
The surface of Orcus is relatively bright with albedo reaching 30%, grey in color and water-rich. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present.

99942 Apophis is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a probability of up to 2.7% that it would hit Earth on April 13, 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a small region no more than about 800 m wide, that would set up a future impact exactly seven years later, on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small. During the short time when it had been most concerning, Apophis set the record for highest rating on the Torino Scale, reaching level 4.
The diameter of Apophis is, as of the most recent 2013 observations, approximately 325 metres. As of May 6, 2013, the probability of an impact on April 13, 2036 has been eliminated.

The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt to distinguish its members from other asteroids in the Solar System such as near-Earth asteroids and trojan asteroids. About half the mass of the belt is contained in the four largest asteroids, Ceres, Vesta, Pallas, and Hygiea. Vesta, Pallas, and Hygiea have mean diameters of more than 400 km, whereas Ceres, the asteroid belt's only dwarf planet, is about 950 km in diameter. The remaining bodies range down to the size of a dust particle. The asteroid material is so thinly distributed that numerous unmanned spacecraft have traversed it without incident. Nonetheless, collisions between large asteroids do occur, and these can form an asteroid family whose members have similar orbital characteristics and compositions. Individual asteroids within the asteroid belt are categorized by their spectra, with most falling into three basic groups: carbonaceous, silicate, and metal-rich.

Ceres is the largest object in the asteroid belt, which lies between the orbits of Mars and Jupiter. It is composed of rock and ice, is 950 km in diameter, containing a third of the mass of the asteroid belt. It is the largest asteroid, and the only dwarf planet in the inner Solar System. It was the first asteroid to be discovered, on 1 January 1801 by Giuseppe Piazzi in Palermo, though at first it was considered to be a planet. The unmanned Dawn spacecraft is scheduled to arrive at Ceres in early 2015.
Ceres appears to be differentiated into a rocky core and icy mantle, and may harbor an internal ocean of liquid water under its surface. The surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clay. In January 2014, emissions of water vapor were detected from several regions of Ceres. This was somewhat unexpected, as large bodies in the asteroid belt do not typically emit vapor, a hallmark of comets.
From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, and hence even at its brightest it is too dim to be seen with the naked eye except under extremely dark skies.

The Jupiter Trojans, commonly called Trojans or Trojan asteroids, are a large group of objects that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of Jupiter's two stable Lagrangian points, L₄ and L₅, that respectively lie 60° ahead of and behind the planet in its orbit. Jupiter Trojans are distributed in two elongated, curved regions around these Lagrangian points with an average semi-major axis of about 5.2 AU.
The first Jupiter Trojan discovered, 588 Achilles, was spotted in 1906 by the German astronomer Max Wolf. A total of 5,947 Jupiter Trojans have been found as of February 2014. The term "Trojan" derives from the fact that, by convention, they are each named after a mythological figure from the Trojan War. The total number of Jupiter Trojans larger than 1 km in diameter is believed to be about 1 million, approximately equal to the number of asteroids larger than 1 km in the asteroid belt. Like main-belt asteroids, Jupiter Trojans form families.
Jupiter Trojans are dark bodies with reddish, featureless spectra.

50000 Quaoar is a large Kuiper belt object with one known moon. It is probably a dwarf planet.

51 Pegasi b, sometimes unofficially named Bellerophon, is an extrasolar planet approximately 50 light-years away in the constellation of Pegasus. 51 Pegasi b was the first planet to be discovered orbiting a main-sequence star, the Sun-like 51 Pegasi, and marked a breakthrough in astronomical research. It is the prototype for a class of planets called hot Jupiters.

55 Cancri e is an extrasolar planet orbiting the Sun-like star 55 Cancri A. Its mass is about 7.8 Earth masses and its diameter is about twice that of Earth's, thus classifying it as the first Super-Earth discovered around a main sequence star, predating Gliese 876 d by a year. It takes less than 18 hours to complete an orbit and is the innermost known planet in its planetary system. 55 Cancri e was discovered on August 30, 2004. However, until the 2010 observations and recalculations, this planet had been thought to take about 2.8 days to orbit the star. In October 2012, it was announced that 55 Cancri e could be a carbon planet.

GJ 1214 b is an exoplanet that orbits the star GJ 1214. The parent star is 42 light-years from the Sun, in the constellation Ophiuchus. The planet was discovered in December 2009. It is a super-Earth because it is larger than Earth but has a mass and radius significantly less than those of the gas giants in the Solar System. After COROT-7b, it was the second such planet to be known and is the first of a new class of planets with small size and relatively low density. GJ 1214 b is also significant because its parent star is relatively near the Sun and because it transits that parent star, which allows the planet's atmosphere to be studied using spectroscopic technologies.
In December 2013, NASA reported that clouds may have been detected in the atmosphere of GJ 1214 b.

Gliese 581 c or Gl 581 c is a planet orbiting the red dwarf Gliese 581. It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.5 times that of the Earth, it is a super-Earth. At the time of discovery, it was the smallest known extrasolar planet around a main-sequence star but on April 21, 2009, another planet orbiting Gliese 581, Gliese 581 e, was announced with an approximate mass of 1.9 Earth masses.
Gliese 581 c gained interest from astronomers because it was reported to be the first potentially Earth-like planet in the habitable zone of its star, with a temperature right for liquid water on its surface, and by extension, potentially capable of supporting extremophile forms of Earth-like life. However, further research casts doubt upon the habitability of Gliese 581 c.
In astronomical terms, the Gliese 581 system is relatively close to Earth, at 20.3 light years in the direction of the constellation of Libra. This distance, along with the declination and right ascension coordinates, give its exact location in our galaxy.

HD 189733 b, more formally HD 189733 Ab, is an extrasolar planet approximately 63 light-years away from the Solar System in the constellation of Vulpecula, the Fox. The planet was discovered orbiting the star HD 189733 A on October 5, 2005, when astronomers in France observed the planet transiting across the face of the star. With a mass 13% higher than that of Jupiter, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.5 kilometres per second, making it a hot Jupiter with poor prospects for life as we know it. Being the closest transiting hot Jupiter to Earth, HD 189733 b is a subject for extensive atmospheric examination. HD 189733 b was the first extrasolar planet for which a thermal map was constructed, to be detected through polarimetry, to have its overall colour determined, to have a transit detected in x-ray spectrum and to have carbon dioxide in its atmosphere.
In July, 2014, NASA announced finding very dry atmospheres on three exoplanets orbiting Sun-like stars.

Haumea, minor-planet designation 136108 Haumea, is a dwarf planet located beyond Neptune's orbit. Just one-third the mass of Pluto, it was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory in the United States and, in 2005, by a team headed by J. L. Ortiz at the Sierra Nevada Observatory in Spain, though the latter claim has been contested. On September 17, 2008, it was recognized as a dwarf planet by the International Astronomical Union and named after Haumea, the Hawaiian goddess of childbirth.
Haumea's extreme elongation makes it unique among known dwarf planets. Although its shape has not been directly observed, calculations from its light curve suggest it is an ellipsoid, with its major axis twice as long as its minor. Nonetheless, its gravity is believed sufficient for it to have relaxed into hydrostatic equilibrium, making it a dwarf planet. This elongation, along with its unusually rapid rotation, high density, and high albedo, are thought to be the results of a giant collision, which left Haumea the largest member of a collisional family that includes several large trans-Neptunian objects and its two known moons, Hi'iaka and Namaka.

Kerberos is a small natural satellite of Pluto whose existence was announced on July 20, 2011. Its discovery, following the discoveries of Charon in 1978 and Nix and Hydra in 2005, made it Pluto's fourth known moon.

Makemake is a dwarf planet and perhaps the largest Kuiper belt object in the classical population, with a diameter that is about 2/3 the size of Pluto. Makemake has no known satellites, which makes it unique among the largest KBOs and means that its mass can only be estimated. Its extremely low average temperature, about 30 K, means its surface is covered with methane, ethane, and possibly nitrogen ices.
Makemake was discovered on March 31, 2005, by a team led by Michael Brown, and announced on July 29, 2005. Initially, it was known as 2005 FY₉ and later given the minor-planet number 136472. Makemake was recognized as a dwarf planet by the International Astronomical Union in July 2008. Its name derives from Makemake in the mythology of the Rapanui people of Easter Island.

SN 1054 is a supernova that was first observed on 4 July 1054, and that lasted for a period of around two years. The event was recorded in contemporary Chinese astronomy, and references to it are also found in a later Japanese document, and in a document from the Arab world. Furthermore, there are a number of proposed, but doubtful, references from European sources recorded in the 15th century, and perhaps a pictograph associated with the Anasazi Pueblo Peoples found near the Peñasco Blanco site in New Mexico.
The remnant of SN 1054, which consists of debris ejected during the explosion, is known as the Crab Nebula. It is located in the sky near the star Zeta Tauri. The core of the exploding star formed a pulsar, called the Crab Pulsar. The nebula and the pulsar it contains are the most studied astronomical objects outside the Solar System. It is one of the few Galactic supernovae where the date of the explosion is well known. The two objects are the most luminous in their respective categories. For these reasons, and because of the important role it has repeatedly played in the modern era, SN 1054 is the best known supernova in the history of astronomy.

SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby dwarf galaxy. It occurred approximately 51.4 kiloparsecs from Earth, approximately 168,000 light-years, close enough that it was visible to the naked eye. It could be seen from the Southern Hemisphere. It was the closest observed supernova since SN 1604, which occurred in the Milky Way itself. The light from the new supernova reached Earth on February 23, 1987. As it was the first supernova discovered in 1987, it was labeled “1987A”. Its brightness peaked in May with an apparent magnitude of about 3 and slowly declined in the following months. It was the first opportunity for modern astronomers to see a supernova up close and observations have provided much insight into core-collapse supernovae.

Sagittarius A* is a bright and very compact astronomical radio source at the center of the Milky Way galaxy, near the border of the constellations Sagittarius and Scorpius. It is part of a larger astronomical feature known as Sagittarius A. Sagittarius A* is believed to be the location of a supermassive black hole, like those that are now generally accepted to be at the centers of most spiral and elliptical galaxies. Observations of the star S2 in orbit around Sagittarius A* have been used to show the presence of, and produce data about, the Milky Way's central supermassive black hole, and have led to the conclusion that Sagittarius A* is the site of that black hole.

The Sloan Great Wall is a cosmic structure formed by a giant wall of galaxies. Its discovery was announced from Princeton University on October 20, 2003, by J. Richard Gott III, Mario Jurić, and their colleagues, based on data from the Sloan Digital Sky Survey.
The wall measures 1.38 billion light-years in length, located approximately one billion light-years from Earth. It is approximately 1/60 of the diameter of the observable universe, making it the fifth largest known object after the large quasar groups Clowes-Campusano LQG, U1.11, Huge-LQG, and the galaxy filament Hercules–Corona Borealis Great Wall, respectively.
Until the discovery of the Her–CrB GW in November 2013, it was the largest known galaxy filament.
The Sloan Great Wall is between 1.8-2.7 times longer than the CfA2 Great Wall of galaxies. It also contains several galactic superclusters, the largest and richest of which is named SCl 126. This is located in the highest density region of the structure.
In 2011, it was suggested that the SGW is a chance alignment of three structures, and not a structure in itself.

Algol, known colloquially as the Demon Star, is a bright star in the constellation Perseus. It is one of the best known eclipsing binaries, the first such star to be discovered, and also one of the first variable stars to be discovered. Algol is actually a three-star system in which the large and bright primary Beta Persei A is regularly eclipsed by the dimmer Beta Persei B. Thus, Algol's magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every 2 days, 20 hours and 49 minutes during the roughly 10-hour long partial eclipses. There is also a secondary eclipse when the brighter star occults the fainter secondary. This secondary eclipse can only be detected photoelectrically. Algol gives its name to its class of eclipsing variable, known as Algol variables.

Alpha Centauri or Toliman is the brightest star in the southern constellation of Centaurus and the third brightest star in the night sky. The Alpha Centauri system is located 1.34 parsecs or 4.37 light years from the Sun, making it the closest star system to our Solar System. Although it appears to the unaided eye as a single object, Alpha Centauri is actually a binary star system whose combined visual magnitude of −0.27 makes it the third brightest star seen from Earth after the −1.46 magnitude Sirius and the −0.72 magnitude Canopus.
Its component stars are named Alpha Centauri A, with 110% of the mass and 151.9% the luminosity of the Sun, and Alpha Centauri B, at 90.7% of the Sun's mass and 44.5% of its luminosity. During the pair's 79.91-year orbit about a common center, the distance between them varies from about that between Pluto and the Sun to that between Saturn and the Sun.
A third star, known as Proxima Centauri, Proxima, or Alpha Centauri C, is probably gravitationally associated with Alpha Centauri AB.

Antares, also known by its Bayer designation Alpha Scorpii, is the seventeenth brightest star in the nighttime sky and the brightest star in the constellation Scorpius, and is often referred to as "the heart of the scorpion". Along with Aldebaran, Regulus, and Fomalhaut, Antares comprises the group known as the 'Royal stars of Persia'. It is one of the four brightest stars near the ecliptic.
Distinctly reddish when viewed with the unaided eye, Antares is a red supergiant of spectral type M2Iab and is one of the largest and most luminous observable stars. It is a slow irregular variable star with an average magnitude of +1.09. Antares is the brightest, most massive, and most evolved stellar member of the nearest OB association. Antares is a member of the Upper Scorpius subgroup of the Scorpius-Centaurus Association, which contains thousands of stars with mean age 11 million years at a distance of approximately 145 parsecs.

The Beehive Cluster, also known as Praesepe, M44, NGC 2632, or Cr 189, is an open cluster in the constellation Cancer. It is one of the nearest open clusters to the Solar System, and it contains a larger star population than most other nearby clusters. Under dark skies the Beehive Cluster looks like a nebulous object to the naked eye; thus it has been known since ancient times. The classical astronomer Ptolemy called it "the nebulous mass in the breast of Cancer," and it was among the first objects that Galileo studied with his telescope.
The cluster's age and proper motion coincide with those of the Hyades open cluster, suggesting that both share a similar origin. Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with main sequence stars of spectral classes A, F, G, K, and M.
The cluster's distance is often cited to lie between 160 to 187 parsecs. The 2009 catalog of revised Hipparcos parallaxes for Praesepe members and the latest iteration of color-magnitude diagram fitting in the infrared favor an analogous distance near 182 pc. There is better agreement on its age, at about 600 million years.

The Butterfly Cluster is an open cluster of stars in the constellation of Scorpius. Its name derives from the vague resemblance of its shape to a butterfly.
The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham, Jr has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbor the Ptolemy Cluster. Charles Messier catalogued the cluster as M6 in 1764. It was not till the 20th century that star counts, distance, and other properties were measured.

Cygnus X-1 is a well-known galactic X-ray source and black hole candidate in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 2.3×10^−23 W m−2 Hz−1. Cygnus X-1 was the first X-ray source widely accepted to be a black hole candidate and it remains among the most studied astronomical objects in its class. It is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too compact to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon is about 44 km.
Cygnus X-1 belongs to a high-mass X-ray binary system about 6,070 light-years from the Sun that includes a blue supergiant variable star designated HDE 226868 which it orbits at about 0.2 AU, or 20% of the distance from the Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays.

An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived blue stars forged in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. The first known H II region was the Orion Nebula, which was discovered in 1610 by Nicolas-Claude Fabri de Peiresc.
H II regions are named for the large amount of ionised atomic hydrogen they contain, referred to as H II, pronounced H-two by astronomers. Such regions have extremely diverse shapes, because the distribution of the stars and gas inside them is irregular. They often appear clumpy and filamentary, sometimes showing bizarre shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars over a period of several million years. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases of the H II region, leaving behind a cluster of birthed stars such as the Pleiades.

HD 98800, also catalogued as TV Crateris, is a quadruple star system approximately 150 light-years away in the constellation of Crater. The system is located within the TW Hydrae association. The system consists of "HD 98800 A" and "HD 98800 B" each of which contains two stars.
In 2007, a debris disk was discovered orbiting "HD 98800 B" consisting of two rings which indicates there may be an extrasolar planet orbiting within a distance of 1.5 to 2 astronomical units.

The Hyades, is the nearest open cluster to the Solar System and one of the best-studied of all star clusters. The Hipparcos satellite, the Hubble Space Telescope, and infrared color-magnitude diagram fitting have been used to establish a distance of ~153 ly to the cluster center. The distances established by these three independent methods agree, thereby making the Hyades an important rung on the cosmic distance ladder. The cluster consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical content, and motion through space. From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still brighter red giant Aldebaran. However, Aldebaran is unrelated to the Hyades, as it is located much closer to Earth and merely happens to lie along the same line of sight.
The five brightest member stars of the Hyades have all evolved away from the Main Sequence and now lie at the bottom of the giant branch.

The Local Group is the group of galaxies that includes the Milky Way, among others. It comprises more than 54 galaxies, including numerous dwarf galaxies. Its gravitational center is located somewhere between the Milky Way and the Andromeda galaxies. The Local Group covers a diameter of 10 megalight-years and has a binary distribution. The group is estimated to have a total mass of 1.29±0.14 ×10^12 M☉ and has a velocity dispersion of 61±8 km/s. The group itself is part of the Virgo Supercluster.
The two most massive members of the group are the Milky Way and Andromeda galaxies. These two spiral galaxies each have a system of satellite galaxies.
Milky Way's satellite system consists of Sagittarius Dwarf Galaxy, Large Magellanic Cloud, Small Magellanic Cloud, Canis Major Dwarf, Ursa Minor Dwarf, Draco Dwarf, Carina Dwarf, Sextans Dwarf, Sculptor Dwarf, Fornax Dwarf, Leo I, Leo II, and Ursa Major I Dwarf and Ursa Major II Dwarf.

Messier 7 or M7, also designated NGC 6475 and sometimes known as the Ptolemy Cluster, is an open cluster of stars in the constellation of Scorpius. The cluster is easily detectable with the naked eye, close to the "stinger" of Scorpius. With a declination of -34.8°, it is the southernmost Messier object.
M7 has been known since antiquity; it was first recorded by the 1st-century Greek-Roman astronomer Ptolemy, who described it as a nebula in 130 AD. Italian astronomer Giovanni Batista Hodierna observed it before 1654 and counted 30 stars in it. In 1764, French astronomer Charles Messier catalogued the cluster as the seventh member in his list of comet-like objects. English astronomer John Herschel described it as "coarsely scattered clusters of stars".
Telescopic observations of the cluster reveal about 80 stars within a field of view of 1.3° across. At the cluster's estimated distance of 980 light years this corresponds to an actual diameter of 25 light years. The tidal radius of the cluster is 40.1 ly and it has a combined mass of about 735 times the mass of the Sun. The age of the cluster is around 200 million years while the brightest member star is of magnitude 5.6.

The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System. It suggests that the Solar System formed from nebulous material. The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heaven. Originally applied to our own Solar System, this process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular hypothesis is the solar nebular disk model or simply solar nebular model. This nebular hypothesis offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the nebular hypothesis are echoed in modern theories of planetary formation, but most elements have been superseded.
According to the nebular hypothesis, stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds.

Nemesis is a hypothetical red dwarf star or brown dwarf, originally postulated in 1984 to be orbiting the Sun at a distance of about 95,000 AU, somewhat beyond the Oort cloud, to explain a perceived cycle of mass extinctions in the geological record, which seem to occur more often at intervals of 26 million years. As of 2012, over 1800 brown dwarfs have been identified and none of them are inside the Solar System. There are actually fewer brown dwarfs in our cosmic neighborhood than previously thought. Rather than one star for every brown dwarf, there may be as many as six stars for every brown dwarf. The majority of solar-type stars are single.
More recent theories suggest that other forces, like close passage of other stars, or the angular effect of the galactic gravity plane working against the outer solar orbital plane, may be the cause of orbital perturbations of some outer Solar System objects. In 2011, Coryn Bailer-Jones did an analysis of craters on the surface of the Earth and reached the conclusion that the earlier findings of simple periodic patterns to be statistical artifacts, and found that the crater record shows no evidence for Nemesis. However, in 2010, A.L.

In astronomy, the Pleiades, or Seven Sisters, is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky. The celestial entity has several meanings in different cultures and traditions.
The cluster is dominated by hot blue and extremely luminous stars that have formed within the last 100 million years. Dust that forms a faint reflection nebulosity around the brightest stars was thought at first to be left over from the formation of the cluster, but is now known to be an unrelated dust cloud in the interstellar medium, through which the stars are currently passing. Computer simulations have shown that the Pleiades was probably formed from a compact configuration that resembled the Orion Nebula. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.

Procyon is the brightest star in the constellation Canis Minor. To the naked eye, it appears to be a single star, the eighth brightest in the night sky with a visual apparent magnitude of 0.34. It is actually a binary star system, consisting of a white main-sequence star of spectral type F5 IV–V, named Procyon A, and a faint white dwarf companion of spectral type DQZ, named Procyon B. The reason for its brightness is not its intrinsic luminosity but its relative closeness to the Sun; as determined by the European Space Agency Hipparcos astrometry satellite, it lies at a distance of just 11.46 light-years, and is therefore one of our nearest stellar neighbours. Its closest neighbour is Luyten's Star, about 1.12 ly away, and the latter would appear as a visual magnitude 2.7 star in the night sky of a hypothetical planet orbiting Procyon.

A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disc for the star itself, because gasses or other material may be falling from the inner edge of the disk onto the surface of the star. But this process should not be confused with the accretion process thought to build up the planets themselves. Externally illuminated photo-evaporating protoplanetary disks are called proplyds.

R136a1 is a Wolf–Rayet star and the most massive star known. It is an estimated 265 solar masses. It is also the most luminous star known at 8,700,000 times the luminosity of the Sun. It is a member of R136, a super star cluster near the center of the 30 Doradus complex, in the Large Magellanic Cloud.

Regulus is the brightest star in the constellation Leo and one of the brightest stars in the night sky, lying approximately 79 light years from Earth. Regulus is a multiple star system composed of four stars that are organized into two pairs. The spectroscopic binary Regulus A consists of a blue-white main-sequence star and its companion, which has not yet been directly observed, but is probably a white dwarf star. Located farther away is the pair Regulus B and Regulus C, which are dim main-sequence stars.

The Rosette Nebula is a large, circular H II region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The open cluster NGC 2244 is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter.
The complex has the following NGC designations:
NGC 2237 – Part of the nebulous region
NGC 2238 – Part of the nebulous region
NGC 2239 – Part of the nebulous region
NGC 2244 – The open cluster within the nebula
NGC 2246 – Part of the nebulous region
The cluster and nebula lie at a distance of some 5,200 light-years from Earth and measure roughly 130 light years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. The mass of the nebula is estimated to be around 10,000 solar masses.
It is believed that stellar winds from a group of O and B stars are exerting pressure on interstellar clouds to cause compression, followed by star formation in the nebula. This star formation is currently still ongoing.

Spica is the brightest star in the constellation Virgo, and the 15th brightest star in the night sky. It is a blue giant and a variable star of the Beta Cephei type located 250 light years from Earth.

In Christian tradition, the Star of Bethlehem, also called the Christmas Star, revealed the birth of Jesus to the Biblical Magi, and later led them to Bethlehem. The star appears only in the nativity story of the Gospel of Matthew, where magi "from the east" are inspired by the star to travel to Jerusalem. There they meet King Herod of Judea, and ask where the king of the Jews had been born. Herod, following a verse from the Book of Micah interpreted as a prophecy, directs them to Bethlehem. The star leads them to Jesus' home in the town, where they worship him and give him gifts. The wise men are then given a divine warning not to return to Herod so they return home by a different route.
Many Christians see the star as a miraculous sign to mark the birth of the Christ. Some theologians claimed that the star fulfilled a prophecy, known as the Star Prophecy. Astronomers have made several attempts to link the star to unusual astronomical events, such as a conjunction of Jupiter and Saturn, a comet or a supernova.
Many modern scholars do not consider the story to be describing a historical event but a pious fiction created by the author of the Gospel of Matthew.

The Trapezium or Orion Trapezium Cluster, also known by its Bayer designation of Theta¹ Orionis, is a tight open cluster of stars in the heart of the Orion Nebula, in the constellation of Orion. It was discovered by Galileo Galilei. On February 4, 1617 he sketched three of the stars, but missed the surrounding nebulosity. The fourth component was identified by several observers in 1673, and several more components were discovered later, for a total of eight by 1888. Subsequently several of the stars were determined to be binaries. Telescopes of amateur astronomers from about 5 inch aperture can resolve six stars under good seeing conditions.
The Trapezium is a relatively young cluster that has formed directly out of the parent nebula. The five brightest stars are on the order of 15-30 solar masses in size. They are within a diameter of 1.5 light-years of each other and are responsible for much of the illumination of the surrounding nebula. The Trapezium may be a sub-component of the larger Orion Nebula Cluster, a grouping of about 2,000 stars within a diameter of 20 light-years.

The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group is an outlying member. However, the LG experiences the mass of the VC as the Virgocentric flow. It is estimated that the VC's mass is 1.2×10^15 M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.
Many of the brighter galaxies in this cluster, including the giant elliptical galaxy Messier 87, were discovered in the late 1770s and early 1780s and subsequently included in Charles Messier's catalogue of non-cometary fuzzy objects. Described by Messier as nebulae without stars, their true nature was not recognized until the 1920s.
The cluster subtends a maximum arc of approximately 8 degrees centered in the constellation Virgo. Many of the member galaxies of the cluster are visible with a small telescope. Its brightest member is the elliptical galaxy Messier 49; however its most famous member is the also elliptical galaxy Messier 87, that unlike the former is located in the center of the cluster.

The Wild Duck Cluster is an open cluster in the constellation Scutum. It was discovered by Gottfried Kirch in 1681. Charles Messier included it in his catalogue in 1764.
The Wild Duck Cluster is one of the richest and most compact of the known open clusters, containing about 2900 stars. Its age has been estimated to about 220 million years. Its name derives from the brighter stars forming a triangle which could represent a flying flock of ducks.

Messier 13, also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a globular cluster of about 300,000 stars in the constellation of Hercules.

Messier 15 or M15 is a globular cluster in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier's catalogue of comet-like objects in 1764. At an estimated 12.0 billion years old, it is one of the oldest known globular clusters.

Messier 2 or M2 is a globular cluster in the constellation Aquarius, five degrees north of the star Beta Aquarii. It was discovered by Jean-Dominique Maraldi in 1746, and is one of the largest known globular clusters.

Messier 22 is an elliptical globular cluster in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars that is visible in the night sky.

Messier 3 is a globular cluster of stars in the northern constellation of Canes Venatici. It was discovered by Charles Messier on May 3, 1764, and resolved into stars by William Herschel around 1784. Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large variable star population was begun in 1913 by American astronomer Solon Irving Bailey and new variable members continue to be identified up through 2004.
Many amateur astronomers consider it one of the finest northern globular clusters, following only Messier 13. M3 has an apparent magnitude of 6.2, making it a difficult naked eye target even with dark conditions. With a moderate-sized telescope, the cluster is fully defined. It can be a challenge to locate through the technique of star hopping, but can be found by looking almost exactly halfway along an imaginary line connecting the bright star Arcturus to Cor Caroli. Using a telescope with a 25 cm aperture, the cluster has a bright core with a diameter of about 6 arcminutes and spans a total of 12 arcminutes.
This cluster is one of the largest and brightest, and is made up of around 500,000 stars.

Messier 4 or M4 is a globular cluster in the constellation of Scorpius. It was discovered by Philippe Loys de Chéseaux in 1746 and catalogued by Charles Messier in 1764. It was the first globular cluster in which individual stars were resolved.

Messier 5 or M5 is a globular cluster in the constellation Serpens. It was discovered by Gottfried Kirch in 1702.

Messier 80 is a globular cluster in the constellation Scorpius. It was discovered by Charles Messier in 1781.
M80 is located midway between α Scorpii and β Scorpii in a field in the Milky Way that is rich in nebulae. It can be viewed with modest amateur telescopes as a mottled ball of light. With an apparent diameter of about 10' and at an estimated distance of 32,600 light-years, M80's spatial diameter is about 95 light-years. It contains several hundred thousand stars, and is among the more densely populated globular clusters in the Milky Way Galaxy.
M80 contains a relatively large number of blue stragglers, stars that appear to be much younger than the cluster itself. It is thought these stars have lost part of their outer layers due to close encounters with other cluster members or perhaps the result of collisions between stars in the dense cluster. Images from the Hubble Space Telescope have shown districts of very high blue straggler densities, suggesting that the center of the cluster is likely to have a very high capture and collision rate.
On May 21, 1860, a nova was discovered in M80 that attained a magnitude of +7.0.

Messier 9 or M9 is a globular cluster in the constellation of Ophiuchus. It was discovered by Charles Messier in 1764.
M9 is one of the nearer globular clusters to the center of the Milky Way Galaxy with a distance of around 5,500 light-years. Its distance from Earth is 25,800 light-years.
The total luminosity of this cluster is around 120,000 times that of the Sun, the absolute magnitude being -8.04. The brightest individual stars in M9 are of apparent magnitude 13.5, making them visible in moderately sized telescopes. There have been 13 variable stars found in M9.
Nearby, at about 80' to the northeast of M9 is the dimmer globular cluster NGC 6356, while at about 80' to the southeast is the globular NGC 6342.

NGC 1261, also known as Caldwell 87, is a globular cluster in the constellation Horologium, first discovered by James Dunlop in 1826.

NGC 1851 is a globular cluster located in the constellation Columba.

NGC 6397, also known as Caldwell 86, is a globular cluster in the constellation Ara. It is located about 7,200 light-years from Earth, making it one of the two nearest globular clusters to Earth. The cluster contains around 400,000 stars, and can be seen with the naked eye under good observing conditions.
NGC 6397 is one of the at least 20 globular clusters of our Milky Way Galaxy that have undergone a core collapse, meaning that the core has contracted to a very dense stellar agglomeration.

Omega Centauri, or NGC 5139, is a globular cluster in the constellation of Centaurus that was discovered by Edmond Halley in 1677. Located at a distance of 15,800 light-years, it is the largest globular cluster in the Milky Way galaxy at a diameter of roughly 150 light-years. It is estimated to contain approximately 10 million stars and a total mass equivalent to 4 million suns.
Omega Centauri is so distinctive from the other galactic globular clusters that it is thought to have an alternate origin as the core remnant of a disrupted dwarf galaxy.

The Virgo Supercluster or the Local Supercluster is a mass concentration of galaxies which contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs. It is one of millions of superclusters in the observable universe.
A 2014 study indicates that the Virgo Supercluster is only a lobe of a greater supercluster, Laniakea, which is centered on the Great Attractor.

67P/Churyumov–Gerasimenko is a comet with a current orbital period of 6.45 years, a rotation period of approximately 12.4 hours and a maximum velocity of 135,000 km/h. Churyumov–Gerasimenko is approximately 4.1 kilometres by 4.3 kilometres at its widest and longest dimensions. It will next come to perihelion on 13 August 2015. Like most comets, it is named after its discoverers, Soviet astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko. They first observed it on photographic plates in 1969.
Churyumov–Gerasimenko is the destination of the European Space Agency's Rosetta mission, launched on 2 March 2004. Rosetta rendezvoused with Churyumov–Gerasimenko on 6 August 2014 and entered orbit on 10 September 2014. Rosetta '​s lander, Philae, touched down on its surface on 12 November 2014, becoming the first spacecraft to land on a comet nucleus.

Comet Hale–Bopp was perhaps the most widely observed comet of the 20th century and one of the brightest seen for many decades. It was visible to the naked eye for a record 18 months, twice as long as the previous record holder, the Great Comet of 1811.
Hale–Bopp was discovered on July 23, 1995, at a great distance from the Sun, raising expectations that the comet would brighten considerably by the time it passed close to Earth. Although predicting the brightness of comets with any degree of accuracy is very difficult, Hale–Bopp met or exceeded most predictions when it passed perihelion on April 1, 1997. The comet was dubbed the Great Comet of 1997.

Comet Hyakutake is a comet, discovered on 31 January 1996, that passed very close to Earth in March of that year. It was dubbed The Great Comet of 1996; its passage near the Earth was one of the closest cometary approaches of the previous 200 years. Hyakutake appeared very bright in the night sky and was widely seen around the world. The comet temporarily upstaged the much anticipated Comet Hale–Bopp, which was approaching the inner Solar System at the time.
Scientific observations of the comet led to several discoveries. Most surprising to cometary scientists was the first discovery of X-ray emission from a comet, believed to have been caused by ionised solar wind particles interacting with neutral atoms in the coma of the comet. The Ulysses spacecraft unexpectedly crossed the comet's tail at a distance of more than 500 million kilometres from the nucleus, showing that Hyakutake had the longest tail known for a comet.
Hyakutake is a long-period comet. Before its most recent passage through the Solar System, its orbital period was about 17,000 years, but the gravitational perturbation of the giant planets has increased this period to 70,000 years.

Comet Shoemaker–Levy 9 was a comet that broke apart and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects. This generated a large amount of coverage in the popular media, and the comet was closely observed by astronomers worldwide. The collision provided new information about Jupiter and highlighted its role in reducing space debris in the inner Solar System.
The comet was discovered by astronomers Carolyn and Eugene M. Shoemaker and David Levy. Shoemaker–Levy 9, at the time captured by and orbiting Jupiter, was located on the night of March 24, 1993, in a photograph taken with the 40 cm Schmidt telescope at the Palomar Observatory in California. It was the first comet observed to be orbiting a planet, and had probably been captured by the planet around 20 – 30 years earlier.
Calculations showed that its unusual fragmented form was due to a previous closer approach to Jupiter in July 1992. At that time, the orbit of Shoemaker–Levy 9 passed within Jupiter's Roche limit, and Jupiter's tidal forces had acted to pull apart the comet.

Halley's Comet or Comet Halley, officially designated 1P/Halley, is the best-known of the short-period comets and is visible from Earth every 75–76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and the only naked-eye comet that might appear twice in a human lifetime. Halley last appeared in the inner Solar System in 1986 and will next appear in mid-2061.
Halley's returns to the inner Solar System have been observed and recorded by astronomers since at least 240 BC. Clear records of the comet's appearances were made by Chinese, Babylonian, and medieval European chroniclers, but were not recognized as reappearances of the same object at the time. The comet's periodicity was first determined in 1705 by English astronomer Edmond Halley, after whom it is now named.
During its 1986 apparition, Halley's Comet became the first comet to be observed in detail by spacecraft, providing the first observational data on the structure of a comet nucleus and the mechanism of coma and tail formation.

Andromeda is one of the 48 constellations listed by the 2nd-century Greco-Roman astronomer Ptolemy and remains one of the 88 modern constellations. Located north of the celestial equator, it is named for Andromeda, daughter of Cassiopeia, in the Greek myth, who was chained to a rock to be eaten by the sea monster Cetus. Andromeda is most prominent during autumn evenings in the Northern Hemisphere, along with several other constellations named for characters in the Perseus myth. Because of its northern declination, Andromeda is visible only north of 40° south latitude; for observers farther south it lies below the horizon. It is one of the largest constellations, with an area of 722 square degrees. This is over 1,400 times the size of the full moon, 55% of the size of the largest constellation, Hydra, and over 10 times the size of the smallest constellation, Crux.
Its brightest star, Alpha Andromedae, is a binary star that has also been counted as a part of Pegasus, while Gamma Andromedae is a colorful binary and a popular target for amateur astronomers. Only marginally dimmer than Alpha, Beta Andromedae is a red giant, its color visible to the naked eye.

Antlia is a constellation in the southern sky. Its name means "pump" and it specifically represents an air pump. The constellation was created in the 18th century from an undesignated region of sky, so the stars comprising Antlia are faint. Antlia is bordered by Hydra the sea snake, Pyxis the compass, Vela the sails, and Centaurus the centaur. This group of constellations is prominent in the southern sky in late winter and spring. NGC 2997, a spiral galaxy, and the Antlia Dwarf Galaxy lie within Antlia's borders.

Apus is a faint constellation in the southern sky, first defined in the late 16th century. Its name means "no feet" in Greek, and it represents a bird-of-paradise. It is bordered by Triangulum Australe, Circinus, Musca, Chamaeleon, Octans, Pavo and Ara. Its genitive is "Apodis".

Aquarius is a constellation of the zodiac, situated between Capricornus and Pisces. Its name is Latin for "water-carrier" or "cup-carrier", and its symbol is, a representation of water.
Aquarius is one of the oldest of the recognized constellations along the zodiac. It was one of the 48 constellations listed by the 2nd century AD astronomer Ptolemy, and it remains one of the 88 modern constellations. It is found in a region often called the Sea due to its profusion of constellations with watery associations such as Cetus the whale, Pisces the fish, and Eridanus the river.

Aquila is a constellation in the northern sky. Its name is Latin for 'eagle' and it represents the bird who carried Zeus/Jupiter's thunderbolts in Greco-Roman mythology.
Aquila lies just a few degrees North of the celestial equator. The alpha star, Altair, is a vertex of the Summer Triangle asterism. The constellation is best seen in the summer as it is located along the Milky Way. Because of this location along the line of our galaxy, many clusters and nebulae are found within its borders, but they are dim and there are few galaxies.

Ara is a southern constellation situated between Scorpius and Triangulum Australe. Its name is Latin for "altar". Ara was one of the 48 Greek constellations described by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical Union.

Aries is one of the constellations of the zodiac. It is located in the northern celestial hemisphere between Pisces to the west and Taurus to the east. The name Aries is Latin for ram, and its symbol is, representing a ram's horns. It is one of the 48 constellations described by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is a mid-sized constellation, ranking 39th overall size, with an area of 441 square degrees.
Although Aries came to represent specifically the ram whose fleece became the Golden Fleece of Ancient Greek mythology, it has represented a ram since late Babylonian times. Before that, the stars of Aries formed a farmhand. Different cultures have incorporated the stars of Aries into different constellations including twin inspectors in China and a porpoise in the Marshall Islands. Aries is a relatively dim constellation, possessing only four bright stars: Hamal, Sheratan, Mesarthim, and 41 Arietis. The few deep-sky objects within the constellation are quite faint and include several pairs of interacting galaxies. Several meteor showers appear to radiate from Aries, including the Daytime Arietids and the Epsilon Arietids.

Auriga is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Located north of the celestial equator, its name is the Latin word for "charioteer", associating it with various mythological charioteers, including Erichthonius and Myrtilus. Auriga is most prominent during winter evenings in the Northern Hemisphere, along with the five other constellations that have stars in the Winter Hexagon asterism. Because of its northern declination, Auriga is only visible as far as 34° south; for observers farther south it lies partially or fully below the horizon. A large constellation, with an area of 657 square degrees, it is half the size of the largest constellation, Hydra.
Its brightest star, Capella, is an unusual multiple star system among the brightest stars in the night sky. Beta Aurigae is an interesting variable star in the constellation; Epsilon Aurigae, a nearby eclipsing binary with an unusually long period, has been studied intensively. Because of its position near the winter Milky Way, Auriga has many bright open clusters in its borders, including M36, M37, and M38, popular targets for amateur astronomers.

Boötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from the Greek Βοώτης, Boōtēs, meaning herdsman or plowman. The "ö" in the name is a diaeresis, not an umlaut, meaning that each 'o' is to be pronounced separately.
One of the 48 constellations described by the 2nd century astronomer Ptolemy, Boötes is now one of the 88 modern constellations. It contains the fourth brightest star in the night sky, the orange-hued Arcturus. Boötes is home to many other bright stars, including eight above the fourth magnitude and an additional 21 above the fifth magnitude, making a total of 29 stars easily visible to the naked eye.

Caelum is a faint constellation in the southern sky, introduced in the 1750s by Nicolas Louis de Lacaille. Its name means "the chisel" in Latin, and it was formerly known as Caelum Scalptorium. It is the eighth-smallest constellation, and subtends a solid angle of around 0.038 steradians, just less than that of Corona Australis.
Due to its small size and location away from the plane of the Milky Way, Caelum is a rather barren constellation, with few objects of interest. The constellation's brightest star, Alpha Caeli, is only of magnitude 4.45, and only one other star is brighter than magnitude 5. Other notable objects in Caelum are RR Caeli, a binary star with one planet approximately 20.13 parsecs away; X Caeli, a Delta Scuti variable that forms an optical double with Gamma¹ Caeli; and HE0450-2958, a Seyfert galaxy that at first appeared as just a jet with no host galaxy visible.

Camelopardalis or the Giraffe constellation is a large, faint grouping of stars in the northern sky. The constellation was introduced in 1612 by Petrus Plancius. Some older astronomy books give an alternative spelling of the name, Camelopardus.

Cancer is one of the twelve constellations of the zodiac. Its name is Latin for crab and it is commonly represented as one. Its astrological symbol is . Cancer is a medium-size constellation with an area of 506 square degrees and its stars are rather faint, its brightest star Beta Cancri having an apparent magnitude of 3.5. It contains two stars with known planets, including 55 Cancri, which has five: one super-earth and four gas giants, one of which is in the habitable zone and as such has expected temperatures similar to Earth. Located at the center of the constellation is Praesepe, one of the closest open clusters to Earth and a popular target for amateur astronomers.

Canes Venatici is one of the 88 official modern constellations. It is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for "hunting dogs", and the constellation is often depicted in illustrations as representing the dogs of Boötes the Herdsman, a neighboring constellation.

Canis Major is a constellation in the southern celestial hemisphere. In the second century, it was included in Ptolemy's 48 constellations, and is counted among the 88 modern constellations. Its name is Latin for "greater dog" in contrast to Canis Minor, the "lesser dog"; both figures are commonly represented as following the constellation of Orion the hunter. The Milky Way passes through Canis Major and several open clusters lie within its borders.
Canis Major contains Sirius, the brightest star in the night sky, known as the 'dog star'. It is bright because of its proximity to our Solar System. In contrast, the other bright stars of the constellation are stars of great distance and high luminosity. At magnitude 1.5, Epsilon Canis Majoris is the second brightest star of the constellation and one of the brightest sources of ultraviolet radiation in the night sky. Next in brightness are the yellow-white supergiant Delta at 1.8, the blue-white giant Beta at 2.0, blue-white supergiants Eta at 2.4 and Omicron¹ at 3.0, and white spectroscopic binary Zeta, also at 3.0.

Canis Minor is a small constellation in the northern celestial hemisphere. In the second century, it was included as an asterism, or pattern, of two stars in Ptolemy's 48 constellations, and it is counted among the 88 modern constellations. Its name is Latin for "lesser dog", in contrast to Canis Major, the "greater dog"; both figures are commonly represented as following the constellation of Orion the hunter.
Canis Minor contains only two stars brighter than the fourth magnitude, Procyon, with a magnitude of 0.34, and Gomeisa, with a magnitude of 2.9. The constellation's dimmer stars were noted by Johann Bayer, who named eight stars including Alpha and Beta, and John Flamsteed, who numbered fourteen. Procyon is the seventh-brightest star in the night sky, as well as one of the closest. A yellow-white main sequence star, it has a white dwarf companion. Gomeisa is a blue-white main sequence star. Luyten's Star is a ninth-magnitude red dwarf and the Solar System's next closest stellar neighbour in the constellation after Procyon. The fourth-magnitude HD 66141, which has evolved into an orange giant towards the end of its life cycle, was discovered to have a planet in 2012.

Capricornus is one of the constellations of the zodiac; it is often called Capricorn, especially when referring to the corresponding astrological sign. Its name is Latin for "horned goat" or "goat horn", and it is commonly represented in the form of a sea-goat: a mythical creature that is half goat, half fish. Its symbol is .
Capricornus is one of the 88 modern constellations, and was also one of the 48 constellations listed by the 2nd century astronomer Ptolemy. Under its modern boundaries it is bordered by Aquila, Sagittarius, Microscopium, Piscis Austrinus, and Aquarius. The constellation is located in an area of sky called the Sea or the Water, consisting of many water-related constellations such as Aquarius, Pisces and Eridanus. It is the second faintest constellation in the zodiac after Cancer, and it is the smallest constellation in the zodiac.

Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided into three pieces, the other two being Puppis, and Vela.

Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is easily recognizable due to its distinctive 'M' shape when in upper culmination but in higher northern locations when near lower culminations in spring and summer it has a 'W' shape, formed by five bright stars. It is bordered by Andromeda to the south, Perseus to the southeast, and Cepheus to the north. It is opposite the Big Dipper. In northern locations above 34ºN latitude it is visible year-round and in the tropics it can be seen at its clearest in from September to early November in its characteristic 'M' shape. Even in low southern latitudes below 25ºS is can be seen low in the North.

Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. In Greek mythology, Centaurus represents a centaur; a creature that is half human, half horse. Notable stars include Alpha Centauri, the nearest star system to our own Solar System, its neighbour in the sky Beta Centauri, and V766 Centauri, one of the largest stars yet discovered. The constellation also contains Omega Centauri, the brightest globular cluster as visible from Earth and one of the largest known.

Cepheus is a constellation in the northern sky. It is named after Cepheus, King of Aethiopia in Greek mythology. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. Its brightest star is Alpha Cephei with an apparent magnitude of 3.5. Delta Cephei is the prototype of an important class of star known as a Cepheid variable. RW Cephei, an orange hypergiant, together with the red supergiants Mu Cephei, VV Cephei and V354 Cephei are among the largest stars known. In addition, Cepheus also has the hyperluminous quasar S5 0014+81, hosting an ultramassive black hole in its core at 40 billion solar masses, about 10,000 times more massive than the central black hole of the Milky Way, making it the most massive black hole known in the universe.

Cetus is a constellation. Its name refers to Cetus, a sea monster in Greek mythology, although it is often called 'the whale' today. Cetus is located in the region of the sky that contains other water-related constellations such as Aquarius, Pisces, and Eridanus.

Chamaeleon is a small constellation in the southern sky. It is named after the chamaeleon, a kind of lizard. It was first defined in the 16th century.

Circinus is a small faint constellation in the southern sky, first defined in 1756 by French astronomer Nicolas Louis de Lacaille. Its name is Latin for compass, referring to the drafting tool used for drawing circles. Its brightest star is Alpha Circini, with an apparent magnitude of 3.19. Slightly variable, it is the brightest rapidly oscillating Ap star in the night sky. AX Circini is a Cepheid variable visible with the unaided eye, and BX Circini is a faint star thought to have been formed from the merger of two white dwarfs. Two sun-like stars have planetary systems: HD 134060 has two small planets, and HD 129445 has a Jupiter-like planet. Supernova SN 185 appeared in Circinus in 185 AD and was recorded by Chinese observers. Two novae have been observed more recently, in the 20th century.
The Milky Way runs through the constellation, featuring prominent objects such as the open cluster NGC 5823 and the planetary nebula NGC 5315. Circinus hosts one notable spiral galaxy, the Circinus Galaxy, which was discovered in 1977 and is the closest Seyfert galaxy to the Milky Way. The Alpha Circinids, a meteor shower also discovered in 1977, radiate from this constellation.

Columba is a small, faint constellation created in the late sixteenth century. Its name is Latin for dove. It is located just south of Canis Major and Lepus.

Coma Berenices is a traditional asterism that has since been defined as one of the 88 modern constellations. It is located near Arcturus, and the constellation Leo to which it formerly belonged, and contains the North Galactic Pole. Its name means "Berenice's Hair", and refers to the legend of Queen Berenice II of Egypt, who sacrificed her long hair.

Corona Australis or Corona Austrina is a constellation in the Southern Celestial Hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax.
Although fainter than its namesake, the oval- or horseshoe-shaped pattern of its brighter stars renders it distinctive. Alpha and Beta Coronae Australis are the two brightest stars with an apparent magnitude of around 4.1. Epsilon Coronae Australis is the brightest example of a W Ursae Majoris variable in the southern sky. Lying alongside the Milky Way, Corona Australis contains one of the closest star-forming regions to our Solar System—a dusty dark nebula known as the Corona Australis Molecular Cloud, lying about 430 light years away. Within it are stars at the earliest stages of their lifespan.

Corona Borealis is a small constellation in the Northern Celestial Hemisphere. Its Latin name means "northern crown", a name inspired by its shape; its main stars form a semicircular arc. It is the northern counterpart of Corona Australis, the southern crown. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations.
The brightest star is the 2.2-magnitude Alpha Coronae Borealis. Four star systems have been found to have exoplanets to date; three of these are orange giants, while the fourth—Rho Coronae Borealis—is a solar twin, very like our own Sun. The yellow supergiant R Coronae Borealis is the prototype of a rare class of unusual stars—the R Coronae Borealis variables—that are extremely hydrogen deficient, and thought to result from the merger of two white dwarfs. Abell 2065 is a highly concentrated galaxy cluster located one billion light-years from our Solar System containing over 400 members, the brightest of which are 16th magnitude.

Corvus is a small constellation in the Southern Celestial Hemisphere. Its name comes from the Latin word "raven" or "crow". It includes only 11 stars with brighter than 4.02 magnitudes. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations. The four brightest stars, Gamma, Delta, Epsilon, and Beta Corvi from a distinctive quadrilateral in the night sky.

Crater is a constellation. Its name is Latin for cup, and in Greek mythology it is identified with the cup of the god Apollo. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is faint, with no star brighter than third magnitude.

Crux, located in the deep southern sky, is the smallest yet one of the most distinctive of the 88 modern constellations. Its name is Latin for cross, and it is dominated by a cross-shaped asterism that is commonly known as the Southern Cross. Although visible to the Ancient Greeks, it was seen as part of the constellation Centaurus, and not defined or accurately mapped till the 16th century.
Known as Acrux, blue-white Alpha Crucis is the constellation's brightest star and the bottom star of the cross. Nearly as bright are Beta and Gamma, while Delta and Epsilon make up the asterism. Many of the constellation's brighter stars are members of the Scorpius–Centaurus Association, a loose group of hot blue-white stars that appear to share a common origin and motion across the Milky Way. Two star systems have been found to have planets. The constellation also contains four Cepheid variables visible to the naked eye under optimum conditions. Crux also contains the Jewel Box, a bright open cluster, and the Coalsack Nebula, the most prominent dark nebula in the sky.

Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. The swan is one of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.
Cygnus contains Deneb, one of the brightest stars in the night sky and one corner of the Summer Triangle, as well as some notable X-ray sources and the giant stellar association of Cygnus OB2. One of the stars of this association, NML Cygni, is one of the largest stars currently known. The constellation is also home to Cygnus X-1, an distant X-ray binary containing a supergiant and unseen massive companion that was the first object widely held to be a black hole. Many star systems in Cygnus have known planets as a result of the Kepler Mission observing one patch of the sky, the patch is the area around Cygnus.

Delphinus is a constellation in the northern sky, close to the celestial equator. Its name is Latin for dolphin. Delphinus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains among the 88 modern constellations recognized by the International Astronomical Union. It is one of the smaller constellations, ranked 69th in size.
Delphinus' brightest stars form a distinctive asterism that can easily be recognized. It is bordered by Vulpecula the fox, Sagitta the arrow, Aquila the eagle, Aquarius the water-carrier, Equuleus the foal and Pegasus the flying horse.

Dorado is a constellation in the southern sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the dolphinfish, which is known as dorado in Portuguese, although it has also been depicted as a swordfish. Dorado is notable for containing most of the Large Magellanic Cloud, the remainder being in the constellation Mensa. The South ecliptic pole also lies within this constellation.
Even though the name Dorado is not Latin but Portuguese, astronomers give it the Latin genitive form Doradus when naming its stars; they are treating it as if it were a feminine proper name of Greek origin ending in -ō, names that have a genitive ending in -ūs.

Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar for many observers in the northern hemisphere. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations today. The north pole of the ecliptic is in Draco. Draco can be seen all year.

Equuleus is a constellation. Its name is Latin for 'horse', a foal. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is the second smallest of the modern constellations, spanning only 72 square degrees. It is also very faint, having no stars brighter than the fourth magnitude.

The modern constellation Eridanus lies across one of the quadrants symbolized by the The White Tiger of the West, and The Southern Asterisms, that divide the sky in traditional Chinese uranography.
According to the quadrant, it is possible that the constellation Eridanus is not fully visible. Achernar is bright star in this constellation that may have never been seen in Chinese skies.
The name of the western constellation in modern Chinese is 波江座, meaning "the waving river constellation".

Fornax is a constellation in the southern sky. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 modern constellations.

Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century AD astronomer Ptolemy and it remains one of the 88 modern constellations today. Its name is Latin for "twins," and it is associated with the twins Castor and Pollux in Greek mythology. Its symbol is .

Grus is a constellation in the southern sky. Its name is Latin for the crane, a type of bird. It is one of twelve constellations conceived by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. Grus first appeared on a 35-cm diameter celestial globe published in 1598 in Amsterdam by Plancius and Jodocus Hondius and was depicted in Johann Bayer's star atlas Uranometria of 1603. French explorer and astronomer Nicolas Louis de Lacaille gave Bayer designations to its stars in 1756, some of which had been previously considered part of the neighbouring constellation Piscis Austrinus. The constellations Grus, Pavo, Phoenix and Tucana are collectively known as the "Southern Birds".
The constellation's brightest star, Alpha Gruis, is also known as Alnair and appears as a 1.7-magnitude blue-white star. Beta Gruis is a red giant variable star with a minimum magnitude of 2.3 and a maximum magnitude of 2.0. Six star systems have been found to have planets: the red dwarf Gliese 832 is one of the closest stars to Earth that has a planetary system. Another—WASP-95—has a planet that orbits every two days.

Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is the fifth largest of the modern constellations.

Horologium is a small and faint constellation in the southern sky. Its name is a Latin transliteration of the Greek word for clock.

Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees. Also one of the longest at over 100 degrees, its southern end abuts Libra and Centaurus and its northern end borders Cancer. It has a long history, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake.

Hydrus is a small constellation in the deep southern sky. It was first depicted on a celestial atlas by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted the brighter stars and gave their Bayer designations in 1756. Its name means "male water snake", as opposed to Hydra, a much larger constellation that represents a female water snake. It remains below the horizon for most Northern Hemisphere observers.
The brightest star is the 2.8-magnitude Beta Hydri, also the closest reasonably bright star to the south celestial pole. Pulsating between magnitude 3.26 and 3.33, Gamma Hydri is a variable red giant some 60 times the diameter of our Sun. Lying near it is VW Hydri, one of the brightest dwarf novae in the heavens. Four star systems have been found to have exoplanets to date, most notably HD 10180, which could bear up to nine planetary companions.

Indus is a constellation in the southern sky. Created in the late sixteenth century, it represents an Indian, a word that could refer at the time to any native of Asia or the Americas.

Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for lizard. A small, faint constellation, it was created in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a "W" shape similar to that of Cassiopeia, and it is thus sometimes referred to as 'Little Cassiopeia'. It is located between Cygnus, Cassiopeia and Andromeda on the northern celestial sphere. The northern part lies on the Milky Way.

Leo is one of the constellations of the zodiac, lying between Cancer to the west and Virgo to the east. Its name is Latin for lion, and to the ancient Greeks represented the Nemean Lion killed by the mythical Greek hero Heracles as one of his twelve labors. Its symbol is . One of the 48 constellations described by the 2nd century astronomer Ptolemy, Leo remains one of the 88 modern constellations today, and one of the most easily recognizable due to its many bright stars and a distinctive shape that is reminiscent of the crouching lion it depicts. The lion's mane and shoulders also form an asterism known as "the Sickle," which to modern observers may resemble a backwards "question mark."

Leo Minor is a small and faint constellation in the northern celestial hemisphere. Its name is Latin for "the smaller lion", in contrast to Leo, the larger lion. It lies between the larger and more recognizable Ursa Major to the north and Leo to the south. Leo Minor was not regarded as a separate constellation by classical astronomers; it was designated by Johannes Hevelius in 1687.
There are 37 stars brighter than apparent magnitude 6.5 in the constellation; three are brighter than magnitude 4.5. 46 Leonis Minoris, an orange giant of magnitude 3.8, is located some 95 light-years from Earth. At magnitude 4.4, Beta Leonis Minoris is the second brightest star and the only one in the constellation with a Bayer designation. It is a binary star, the brighter component of which is an orange giant and the fainter a yellow-white main sequence star. The third brightest star is 21 Leonis Minoris, a rapidly rotating white main-sequence star of average magnitude 4.5. The constellation also includes two stars with planetary systems, two pairs of interacting galaxies, and the unique deep-sky object Hanny's Voorwerp.

Lepus is a constellation lying just south of the celestial equator, immediately south of Orion. Its name is Latin for hare. Although the hare does not represent any particular figure in Greek mythology, Lepus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is located below the constellation Orion, and is sometimes represented as a hare being chased by Orion or, alternatively, by Orion's hunting dogs.

Libra is a constellation of the zodiac. Its name is Latin for weighing scales, and its symbol is . It is fairly faint, with no first magnitude stars, and lies between Virgo to the west and Scorpius to the east.

Lupus is a constellation in the southern sky. Its name is Latin for wolf. Lupus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It lies between Centaurus and Scorpius.

Lynx is a constellation in the northern sky, introduced in the 17th century by Johannes Hevelius. It is named after the lynx, a genus of cat. It is a very faint constellation; its brightest stars form a zigzag line.

Lyra is a small constellation. It is one of 48 listed by the 2nd century astronomer Ptolemy, and is one of the 88 constellations recognized by the International Astronomical Union. Its principal star, Vega, a corner of the Summer Triangle, is one of the brightest stars in the sky. Beginning at the north, Lyra is bordered by Draco, Hercules, Vulpecula, and Cygnus.
Lyra is visible from the northern hemisphere from spring through autumn, and nearly overhead, in temperate latitudes, during the summer months. From the southern hemisphere, it is visible low in the northern sky during the winter months.

Mensa is a constellation in the southern sky, created in the 18th century. Its name is Latin for table. It covers a keystone-shaped wedge of sky stretching from approximately 4h to 7.5h of right ascension, and −71 to −85.5 degrees of declination. Other than the south polar constellation of Octans, it is the most southerly of constellations. As a result, it is essentially unobservable from the Northern Hemisphere. Besides those already mentioned, its other neighbouring constellations are Chamaeleon, Dorado, Hydrus, and Volans. It is the only constellation named after a feature on Earth.

Microscopium is a small constellation in the southern sky, defined in the 18th century by Nicolas Louis de Lacaille. Its brightest star is Gamma Microscopii of apparent magnitude 4.68, actually a yellow giant located around 381 light-years distant. Two star systems—WASP-7 and HD 205739—have been found to have planets, while another—AU Microscopii—has a debris disk.

Monoceros is a faint constellation on the celestial equator. Its name is Greek for unicorn. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the south and Hydra to the east. Other bordering constellations include Canis Minor, Lepus and Puppis.

Musca is a small constellation in the deep southern sky. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm diameter celestial globe published in 1597 in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. It was also known as Apis for two hundred years. Musca remains below the horizon for most Northern Hemisphere observers.
Many of the constellation's brighter stars are members of the Scorpius–Centaurus Association, a loose group of hot blue-white stars that appear to share a common origin and motion across the Milky Way. These include Alpha, Beta, Gamma, Zeta² and Eta Muscae, as well as HD 100546, a blue-white Herbig Ae/Be star that is surrounded by a complex debris disk containing a large planet or brown dwarf and possible protoplanet. Two further star systems have been found to have planets. The constellation also contains two Cepheid variables visible to the naked eye. Theta Muscae is a triple star system, the brightest member of which is a Wolf–Rayet star.

Norma is a small and inconspicuous constellation in the southern hemisphere between Scorpius and Centaurus. Its name is Latin for normal, referring to a right angle, and is variously considered to represent a rule, a carpenter's square, a set square or a level.

Octans is a faint constellation of the southern sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. The constellation was devised by Nicolas Louis de Lacaille in the eighteenth century.
Octans is notable as the location of the south celestial pole. Unlike the north pole, it has no bright pole star: Sigma Octantis is a naked-eye star very close to the pole, but it is so faint that it is practically useless for navigation purposes. Conveniently for navigators, the constellation Crux, the Southern Cross, points toward the pole.
The constellation is circumpolar to the south celestial pole, so it can be seen in Southern Hemisphere skies during the evening in any month of the year. The Right Ascension and month of best visibility given are for the three brightest stars, which are at their highest in the sky during the evening in November.

Ophiuchus is a large constellation located around the celestial equator. Its name is from the Greek Ὀφιοῦχος "serpent-bearer", and it is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. It was formerly referred to as Serpentarius and Anguitenens.

Orion is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous and recognizable constellations in the night sky. It was named after Orion, a hunter in Greek mythology. Its brightest stars are Rigel and Betelgeuse, a blue-white and a red supergiant.

Pavo is a constellation in the southern sky with the Latin name for peacock. It is one of twelve constellations conceived by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. Pavo first appeared on a 35-cm diameter celestial globe published in 1598 in Amsterdam by Plancius and Jodocus Hondius and was depicted in Johann Bayer's star atlas Uranometria of 1603. French explorer and astronomer Nicolas Louis de Lacaille gave its stars Bayer designations in 1756. The constellations Pavo, Grus, Phoenix and Tucana are collectively known as the "Southern Birds".
The constellation's brightest member, Alpha Pavonis, is also known as Peacock and appears as a 1.91-magnitude blue-white star, but is actually a spectroscopic binary. Delta Pavonis is a nearby Sun-like star some 19.9 light years distant. Six of the star systems in Pavo have been found to host planets, including HD 181433 with a super-earth, and HD 172555 with evidence of a major interplanetary collision in the past few thousand years.

Pegasus is a constellation in the northern sky, named after the winged horse Pegasus in Greek mythology. It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations.
With an apparent magnitude varying between 2.37 and 2.45, the brightest star in Pegasus is the orange supergiant Epsilon Pegasi, also known as Enif, which marks the horse's muzzle. Alpha, Beta, and Gamma, together with Alpha Andromedae form the large asterism known as the Square of Pegasus. Twelve star systems have been found to have exoplanets.

Perseus, named after the Greek mythological hero Perseus, is a constellation in the northern sky. It was one of 48 listed by the 2nd-century astronomer Ptolemy and among the 88 modern constellations defined by the International Astronomical Union. It is located in the northern celestial hemisphere near several other constellations named after legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west.
The galactic plane of the Milky Way passes through Perseus but is mostly obscured by molecular clouds. The constellation's brightest star is the yellow-white supergiant Alpha Persei, which shines at magnitude 1.79. It and many of the surrounding stars are members of an open cluster known as the Alpha Persei Cluster. The best-known star, however, is Algol, linked with ominous legends because of its variability, which is noticeable to the naked eye. Rather than being an intrinsically variable star, it is an eclipsing binary.

Phoenix is a minor constellation in the southern sky. Named after the mythical phoenix, it was first depicted on a celestial atlas by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted the brighter stars and gave their Bayer designations in 1756. The constellation stretches from roughly −39° to −57° declination, and from 23.5h to 2.5h of right ascension. The constellations Phoenix, Grus, Pavo and Tucana, are known as the Southern Birds.
The brightest star, Alpha Phoenicis, is named Ankaa, an Arabic word meaning 'the Phoenix'. It is an orange giant of apparent magnitude 2.4. Next is Beta Phoenicis, actually a binary system composed of two yellow giants with a combined apparent magnitude of 3.3. Nu Phoenicis has a dust disk, while the constellation has ten star systems with known planets and the recently discovered galaxy clusters El Gordo and the Phoenix Cluster—located 7.2 and 5.7 billion light years away respectively, two of the largest objects in the visible universe. Phoenix is the radiant of two annual meteor showers: the Phoenicids in December, and the July Phoenicids.

Pictor is a small faint constellation in the Southern Celestial Hemisphere, located between the brilliant star Canopus and the Large Magellanic Cloud. Latin for painter, its name is an abbreviation of the older name Equuleus Pictoris. Normally represented as an easel, Pictor was invented and named by Abbé Nicolas Louis de Lacaille in the 18th century. The constellation's brightest star is Alpha Pictoris, a white main sequence star of apparent magnitude 3.3 around 97 light-years away from Earth. Pictor also hosts RR Pictoris, a cataclysmic variable star system that flared up as a nova, reaching magnitude 1.2 in 1925 before fading into obscurity.
Pictor has attracted attention because of its second-brightest star Beta Pictoris, 63.4 light-years distant from Earth, which is surrounded by an unusual dust disk rich in carbon, as well as an exoplanet. Another five stars in the constellation have been found to have planets. Among them is HD 40307, an orange dwarf that has six planets orbiting it, one of which—HD 40307 g—is a potential super-Earth in the circumstellar habitable zone.

Pisces is a constellation of the zodiac. Its name is the Latin plural for fish, and its symbol is ♓ . It lies between Aquarius to the west and Aries to the east. The ecliptic and the celestial equator intersect within this constellation and in Virgo.

Piscis Austrinus is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish", in contrast with the larger constellation Pisces, which represents a pair of fishes. Prior to the 20th century, it was also known as Piscis Notius. Its only star brighter than 4th magnitude is Fomalhaut, which is a first-magnitude star and is the 18th brightest star in the night sky.
Piscis Austrinus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. The stars of the modern constellation Grus once formed the "tail" of Piscis Austrinus. In 1597, Petrus Plancius carved out a separate constellation and named it after the crane.
In Greek mythology, this constellation is known as the Great Fish and it is portrayed as swallowing the water being poured out by Aquarius, the water-bearer constellation. The two fish of the constellation Pisces are said to be the offspring of the Great Fish. In Egyptian mythology, this fish saved the life of the Egyptian goddess Isis, so she placed this fish and its descendants into the heavens as constellations of stars.

Puppis is a constellation in the southern sky. Puppis, the Poop Deck, was originally part of an over-large constellation, the ship of "Jason and the Argonauts", Argo Navis, which centuries after its initial description, was divided into three parts, the other two being Carina, and Vela. Puppis is the largest of the three constellations in square degrees. It is one of the 88 modern constellations recognized by the International Astronomical Union.

Pyxis is a small and faint constellation in the southern sky. Its name is Latin for a mariner's compass. Pyxis is completely visible from latitudes south of 53 degrees north, with its best evening-sky visibility in January through March. The brightest star is Alpha Pyxidis at magnitude 3.68.
Pyxis was introduced by Nicolas Louis de Lacaille in the 18th century; he called it Pyxis Nautica, but the name was shortened. The constellation is located close to those forming the old constellation of Argo Navis, and in the 19th century astronomer John Herschel suggested renaming Pyxis to 'Malus, the mast', but the suggestion was not followed.

Rangifer was a small constellation located between the constellations of Cassiopeia and Camelopardalis. It is also known as Tarandus. Both words mean "reindeer" in Latin. "Rangifer" is the generic name of the reindeer, and "tarandus" is the specific name.

Reticulum is a small, faint constellation in the southern sky. Its name is Latin for a small net, or reticle—a net of crosshairs at the focus of a telescope eyepiece that is used to measure star positions. The constellation is best viewed between October and December, but cannot be seen from middle to northern latitudes.

Sagitta is a constellation. Its name is Latin for "arrow", and it should not be confused with the larger constellation Sagittarius, the archer. Although Sagitta is an ancient constellation, it has no star brighter than 3rd magnitude and has the third-smallest area of all constellations. It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical Union. Located to the north of the equator, Sagitta can be seen from every location on Earth except within the Antarctic circle.
Sagitta lies within the Milky Way and is bordered by the following constellations: the little fox Vulpecula, the mythological hero Hercules, the eagle Aquila and the dolphin Delphinus.

Sagittarius is one of the constellations of the zodiac. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its name is Latin for the archer, and its symbol is, a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus to the east.

Scorpius, sometimes known as Scorpio, is one of the constellations of the zodiac. Its name is Latin for scorpion, and its symbol is . It lies between Libra to the west and Sagittarius to the east. It is a large constellation located in the southern hemisphere near the center of the Milky Way.

Sculptor is a small and faint constellation in the southern sky. It represents a sculptor. It was introduced by Nicolas Louis de Lacaille in the 18th century. He originally named it Apparatus Sculptoris, but the name was later shortened.

Scutum is a small constellation introduced in the seventeenth century. Its name is Latin for shield.

Serpens is a constellation of the northern hemisphere. One of the 48 constellations listed by the 2nd century astronomer Ptolemy, it remains one of the 88 modern constellations defined by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput to the west and Serpens Cauda to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between μ Ser in Serpens Caput and ν Ser in Serpens Cauda.
The brightest star in Serpens is Unukalhai or Cor Serpentis "Serpent's Heart", with an apparent magnitude of 2.63. Part of the Milky Way passes through Serpens Cauda, which is therefore rich in deep-sky objects, such as the Eagle Nebula and its associated star cluster Messier 16. The nebula measures 70 light-years by 50 light-years and contains the Pillars of Creation, three dust clouds that became famous for the image taken by the Hubble Space Telescope.

Sextans is a minor equatorial constellation which was introduced in 1687 by Johannes Hevelius. Its name is Latin for the astronomical sextant, an instrument that Hevelius made frequent use of in his observations.

Taurus is one of the constellations of the zodiac, which means it is crossed by the plane of the ecliptic. Its name is a Latin word meaning "bull", and its astrological symbol is a stylized bull's head: . Taurus is a large and prominent constellation in the northern hemisphere's winter sky. It is one of the oldest constellations, dating back to at least the Early Bronze Age when it marked the location of the Sun during the spring equinox. Taurus came to symbolize the bull in the mythologies of Ancient Babylon, Egypt, and Greece.
There are a number of features of interest to astronomers. Taurus hosts two of the nearest open clusters to Earth, the Pleiades and the Hyades, both of which are visible to the naked eye. At first magnitude, the red giant Aldebaran is the brightest star in the constellation. In the northwest part of Taurus is the supernova remnant Messier 1, more commonly known as the Crab Nebula. One of the closest regions of active star formation, the Taurus-Auriga complex, crosses into the northern part of the constellation. The variable star T Tauri is the prototype of a class of pre-main-sequence stars.

Telescopium is a minor constellation in the southern celestial hemisphere, one of twelve created in the 18th century by French astronomer Nicolas Louis de Lacaille and one of several depicting scientific instruments. Its name is a Latinized form of the Greek word for telescope. Telescopium was later much reduced in size by Francis Baily and Benjamin Gould.
The brightest star in the constellation is Alpha Telescopii, a blue-white subgiant with an apparent magnitude of 3.5, followed by the orange giant star Zeta Telescopii at magnitude 4.1. Eta and PZ Telescopii are two young star systems with debris disks and brown dwarf companions. Telescopium hosts two unusual stars with very little hydrogen that are likely to be the result of two merged white dwarfs: HD 168476, also known as PV Telescopii, is a hot blue extreme helium star, while RS Telescopii is an R Coronae Borealis variable. RR Telescopii is a cataclysmic variable that brightened as a nova to magnitude 6 in 1948.

Triangulum is a small constellation in the northern sky. Its name is Latin for "triangle", derived from its three brightest stars, which form a long and narrow triangle. Known to the ancient Babylonians and Greeks, Triangulum was one of the 48 constellations listed by the 2nd century astronomer Ptolemy. The celestial cartographers Johann Bayer and John Flamsteed catalogued the constellation's stars, giving six of them Bayer designations.
The white stars Beta and Gamma Trianguli, of apparent magnitudes 3.00 and 4.00, respectively, form the base of the triangle and the yellow-white Alpha Trianguli, of magnitude 3.41, the apex. Iota Trianguli is a notable double star system, and there are three star systems with planets located in Triangulum. The constellation contains several galaxies, the brightest and nearest of which is the Triangulum Galaxy or Messier 33 —a member of the Local Group. The first quasar ever observed, 3C 48, also lies within Triangulum's boundaries.

Triangulum Australe is a small constellation in the far southern celestial hemisphere. Its name is Latin for "the southern triangle", which distinguishes it from Triangulum in the northern sky and is derived from the almost equilateral pattern of its three brightest stars. It was first depicted on a celestial globe as Triangulus Antarcticus by Petrus Plancius in 1589, and later with more accuracy and its current name by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted and gave the brighter stars their Bayer designations in 1756.
Alpha Trianguli Australis, known as Atria, is a second magnitude orange giant and the brightest star in the constellation, as well as the 42nd-brightest star in the night sky. Completing the triangle are the two white main sequence stars Beta and Gamma Trianguli Australis. Although the constellation lies in the Milky Way and contains many stars, deep-sky objects are not prominent. Notable features include the open cluster NGC 6025 and planetary nebula NGC 5979.

Tucana is a constellation of stars in the southern sky, named after the toucan, a South American bird. It is one of twelve constellations conceived in the late sixteenth century by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. Tucana first appeared on a 35-cm diameter celestial globe published in 1598 in Amsterdam by Plancius and Jodocus Hondius and was depicted in Johann Bayer's star atlas Uranometria of 1603. French explorer and astronomer Nicolas Louis de Lacaille gave its stars Bayer designations in 1756. The constellations Tucana, Grus, Phoenix and Pavo are collectively known as the "Southern Birds".
Tucana is not a prominent constellation as all of its stars are third magnitude or fainter; the brightest is Alpha Tucanae with an apparent visual magnitude of 2.87. Beta Tucanae is a star system with six member stars, while Kappa is a quadruple system. Five star systems have been found to have exoplanets to date. The constellation contains 47 Tucanae, one of the brightest globular clusters in the sky, and most of the Small Magellanic Cloud.

Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. It can be seen best in the month of April. It is dominated by the widely recognized asterism known as the Big Dipper or the Plough, which is a useful pointer towards the north, and it has mythological significance in numerous world cultures.

Ursa Minor, also known as the Little Bear, is a constellation in the northern sky. Like the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the name Little Dipper. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor is notable as the location of the north celestial pole, although this will change after some centuries due to the precession of the equinoxes.
Polaris, the brightest star in the constellation, is a yellow-white supergiant and brightest Cepheid variable star in the night sky, ranging from apparent magnitude 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab, is only slightly fainter, with its apparent magnitude of 2.08. An ageing star that has swollen and cooled to become an orange giant, it has a been found to have a planet orbiting it in 2014. It and magnitude 3 Gamma Ursae Minoris have been called the 'guardians of the pole star'. Three other stellar systems have been discovered to contain planets.

Vela is a constellation in the southern sky. Its name is Latin for the sails of a ship, and it was originally part of a larger constellation, the ship Argo Navis, which was later divided into three or four parts, the others being Carina, Puppis and, according to some authorities, Pyxis. With an apparent magnitude of 1.8, its brightest star is the hot blue multiple star Gamma Velorum, one component of which is the brightest Wolf-Rayet star in the sky. Delta and Kappa Velorum, together with Epsilon and Iota Carinae, form the asterism known as the False Cross. 1.95-magnitude Delta is actually a triple or quintuple star system.

Virgo is one of the constellations of the zodiac. Its name is Latin for virgin, and its symbol is ♍. Lying between Leo to the west and Libra to the east, it is the second largest constellation in the sky. It can be easily found through its brightest star, Spica.

Volans is a constellation in the southern sky. It represents a flying fish; its name is a shortened form of its original name, Piscis Volans. Volans was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm diameter celestial globe published in 1597 in Amsterdam by Plancius with Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603.

Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is commonly known simply as the fox. It was identified in the seventeenth century, and is located in the middle of the Summer Triangle.

3C75 is a binary black hole system in the Abell 400 cluster of galaxies. It has four radio jets. It is travelling at 1200 kilometers per second through the cluster plasma, causing the jets to be swept back. The binary supermassive black holes are themselves contained in the dumbbell shaped galaxy NGC 1128. 3C 75 may be X-ray source 2A 0252+060.

Abell 1835 IR1916 was a candidate for being the most distant galaxy ever observed, although that claim has not been verified by additional observations. It was claimed to lie behind the galaxy cluster Abell 1835, in the Virgo constellation.

The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the Andromeda constellation. Also known as Messier 31, M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest spiral galaxy to our Milky Way galaxy, but not the nearest galaxy overall. It gets its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. The Andromeda Galaxy is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies.
The Andromeda Galaxy is probably the most massive galaxy in the Local Group as well, despite earlier findings that suggested that the Milky Way contains more dark matter and could be the most massive in the grouping. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion stars: at least twice the number of stars in the Milky Way galaxy, which is estimated to be 200–400 billion.

Andromeda I is a dwarf spheroidal galaxy about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy. It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.
Andromeda I was discovered by Sidney van den Bergh in 1970 with the Mount Palomar Observatory 48-inch telescope. Further study of Andromeda I was done by the WFPC2 camera of the Hubble Space Telescope. This found that the horizontal branch stars, like other dwarf spheroidal galaxies were predominantly red. From this, and the abundance of blue horizontal branch stars, along with 99 RR Lyrae stars detected in 2005, lead to the conclusion there was an extended epoch of star formation. The estimated age is approximately 10 Gyr. The Hubble telescope also found a globular cluster in Andromeda I, being the least luminous galaxy where such a cluster was found.

The Antlia Dwarf is a dwarf spheroidal/irregular galaxy. It lies about 1.3 Mpc from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia Group of galaxies. The galaxy contains stars of all ages, contains significant amounts of gas, and has experienced recent star formation. The Antlia Dwarf is believed to be tidally interacting with the small barred spiral galaxy, NGC 3109.

The Aquarius Dwarf galaxy is a dwarf galaxy and an irregular galaxy, that was first catalogued in 1959 by the DDO survey. Its most distinctive characteristic is that it is one of the few galaxies known to display a blueshift, as it is traveling towards the Milky Way at 137 km/s. Aquarius dwarf is also part of the Aquarius constellation.
Lee et al. 1999 firmly established AqrDIG as a member of the Local Group and derived a distance, using the tip of the red-giant branch, of 950 ± 50 kpc. Its distance from the group's barycenter is also calculated to be 950 kpc, which means that AqrDIG is rather isolated in space. Compared to the even further away SagDIG, it is much less luminous.

Arp 220 is the result of a collision between two galaxies which are now in the process of merging. Located 250 million light-years away in the constellation Serpens, it is the 220th object in Halton Arp's Atlas of Peculiar Galaxies.

The Black Eye Galaxy was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier in 1780. It has a spectacular dark band of absorbing dust in front of the galaxy's bright nucleus, giving rise to its nicknames of the "Black Eye" or "Evil Eye" galaxy. M64 is well known among amateur astronomers because of its appearance in small telescopes. It is a spiral galaxy in the Coma Berenices constellation.

The Boötes Dwarf Galaxy is a galaxy, which appears faint, with a luminosity of 100,000 L☉ and an absolute magnitude of –5.8. It lies about 197 kilolight-years away in the constellation Boötes. This dwarf spheroidal galaxy appears to be tidally disrupted by the Milky Way Galaxy, which it orbits, and has two stellar tails that cross over to form a cross. Tidally disrupted galaxies usually only form one tail.
Like many of the ultrafaint dwarf spheroidals, the entire galaxy appears fainter than the star Rigel.

The Canis Major Dwarf Galaxy or Canis Major Overdensity is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.
The supposed small galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one billion stars in all.
The Canis Major Dwarf Galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way, being located about 25,000 light-years away from our Solar System and 42,000 light-years from the Galactic Center. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the previous contender for closest galaxy to our location in the Milky Way.

The Carina Dwarf Spheroidal galaxy is a dwarf galaxy in the Carina constellation. It was discovered in 1977 with the UK Schmidt Telescope by Cannon et al. The Carina Dwarf Spheroidal galaxy is receding from the Milky Way at 230 km/s and is a satellite galaxy to the Milky Way. The galaxy may also be referred to as ESO 206-G20 or PGC 19441. It appears to have formed several billion years after the formation of the other satellite galaxies of the Milky Way as its older stars are younger than 7 billion years. This makes it a relatively youthful galaxy when compared to the Milky Way, which is estimated to have formed 13.6 billion years ago, or nearly as old as the Universe itself. It probably has a complex star formation history, with three possible distinct bursts of star formation. It is also being tidally disrupted by the Milky Way galaxy.

The Cartwheel Galaxy is a lenticular galaxy and ring galaxy about 500 million light-years away in the constellation Sculptor. It is an estimated 150,000 light-years across, has a mass of about 2.9–4.8 × 10⁹ solar masses, and rotates at 217 km/s.
It was discovered by Fritz Zwicky in 1941. Zwicky considered his discovery to be "one of the most complicated structures awaiting its explanation on the basis of stellar dynamics."
An estimation of the galaxy's span resulted in a conclusion of 150,000 light years, which is slightly larger than the Milky Way.

Centaurus A or NGC 5128 is a prominent galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type and distance. NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth brightest in the sky, making it an ideal amateur astronomy target, although the galaxy is only visible from low northern latitudes and the southern hemisphere.
The center of the galaxy contains a supermassive black hole with a mass equivalent to 55 million solar masses, which ejects a relativistic jet that is responsible for emissions in the X-ray and radio wavelengths. By taking radio observations of the jet separated by a decade, astronomers have determined that the inner parts of the jet are moving at about one half of the speed of light. X-rays are produced farther out as the jet collides with surrounding gases resulting in the creation of highly energetic particles.

The Circinus Galaxy is a Seyfert galaxy in the Circinus constellation - and one of the closest to our Milky Way. It is only 4 degrees below the Galactic plane, and 13 million light-years away. The galaxy is undergoing tumultuous changes, as rings of gas are being ejected from the galaxy. The outermost ring is 700 light-years from the center of the galaxy and the inner ring is 130 light-years out. The Circinus galaxy can be seen using a small telescope, however it was not noticed until 25 years ago because it was obscured by material from our own galaxy. The Circinus Galaxy is a Type II Seyfert galaxy and is one of the closest known active galaxies to the Milky Way, though it is probably slightly further away than Centaurus A.
Circinus Galaxy was a home for SN 1996cr, that has been identified over a decade after it exploded. The supernova was first singled out in 2001 as a bright, variable object in a Chandra image, but it was not confirmed as a supernova until years later.

The Comet Galaxy is a spiral galaxy located 3.2 billion light-years from Earth, in the galaxy cluster Abell 2667, was found with the Hubble Space Telescope. This galaxy has a little more mass than our Milky Way. It was detected on 2 March 2007.

Cygnus A is one of the most famous radio galaxies, and among the strongest radio sources in the sky. It was discovered by Grote Reber in 1939. In 1951, Cygnus A, along with Cassiopeia A, and Puppis A were the first "radio stars" identified with an optical source. Of these, Cygnus A became the first radio galaxy; the other two being nebulae inside the Milky Way. In 1953 Roger Jennison and M K Das Gupta showed it to be a double source. Like all radio galaxies, it contains an active galactic nucleus.
Images of the galaxy in the radio portion of the electromagnetic spectrum show two jets protruding in opposite directions from the galaxy's center. These jets extend many times the width of the portion of the host galaxy which emits radiation at visible wavelengths. At the ends of the jets are two lobes with "hot spots" of more intense radiation at their edges. These hot spots are formed when material from the jets collides with the surrounding intergalactic medium.
Cygnus A appears in Carl Sagan's Contact as the result of beings actively creating a galaxy.

The Draco Dwarf is a spheroidal galaxy which was discovered by Albert George Wilson of Lowell Observatory in 1954 on photographic plates of the National Geographic Society's Palomar Observatory Sky Survey. It is part of the Local Group and a satellite galaxy of the Milky Way galaxy. The Draco Dwarf is situated in the direction of the Draco Constellation at 34.6° above the galactic plane.

The Eyes Galaxies are a pair of galaxies about 52 million light-years away in the constellation Virgo. This galaxy takes its name from its ring structure which made it popular.

The Fornax Dwarf Spheroidal is an elliptical dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. He discovered it while he was in South Africa on photographic plates taken by the 24 inch Bruce refractor at Boyden Observatory, shortly after he discovered the Sculptor Dwarf galaxy.
The galaxy is a satellite of the Milky Way and contains six globular clusters; the largest, NGC 1049, was discovered before the galaxy itself. The galaxy is also receding from the Milky Way at 53 km/s. It mostly contains population II stars.

GR 8 is a gas-rich dwarf irregular galaxy. In 1995, Tolstoy et al. estimated its distance to be ~7.9 Million light-years from Earth. There is still open question regarding if it is a member of the Local Group. It was discovered at the Lick Observatory using the 20-inch astrograph in either 1946, 1947, or 1951.

Hoag's Object is a non-typical galaxy of the type known as a ring galaxy. The appearance of this object has interested amateur astronomers as much as its uncommon structure has fascinated professionals. The galaxy is named after Arthur Allen Hoag who discovered it in 1950 and identified it as either a planetary nebula or a peculiar galaxy with eight billion stars.

I Zwicky 18 is a dwarf irregular galaxy located about 59 million light years away. The galaxy was first identified by Swiss astronomer Fritz Zwicky in a 1930s photographic survey of galaxies. Studies at the Palomar Observatory some 40 years ago led astronomers to believe that the galaxy erupted with star formation billions of years after its galactic neighbors. Galaxies resembling I Zwicky 18's youthful appearance are typically found only in the early universe. The Hubble Space Telescope, however, found faint, older stars contained within the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as ten billion years ago. The galaxy, therefore, may have formed at the same time as most other galaxies.
Spectroscopic observations with ground-based telescopes have shown that I Zwicky 18 is almost exclusively composed of hydrogen and helium, the main ingredients created in the Big Bang. The galaxy's primordial makeup suggests that its rate of star formation has been much lower than that of other galaxies of similar age.

IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by Lewis Swift in 1887. Nicholas Mayall was the first to suggest that the object is extragalactic in 1935. Edwin Hubble suspected it might belong to the Local Group of galaxies, but its status remained uncertain for decades. The radial velocity of IC 10 was measured in 1962, and it was found to be approaching the Milky Way at approximately 350 km/s, strengthening the evidence for its membership in the Local Group. Its membership in the group was finally confirmed in 1996 by direct measurements of its distance based on observations of Cepheids. Despite its closeness, the galaxy is rather difficult to study because it lies near the plane of the Milky Way and is therefore heavily obscured by interstellar matter.
The apparent distance between IC 10 and the Andromeda Galaxy is about the same as the apparent distance between the Andromeda Galaxy and the Triangulum Galaxy, which suggests that IC 10 may belong to the M31 subgroup.
IC 10 is the only known starburst galaxy in the Local Group of galaxies.

IC 1101 is a supergiant elliptical galaxy at the center of the Abell 2029 galaxy cluster, approximately 1.07 billion light-years from Earth.

IC 1296 is a barred spiral galaxy in the constellation Lyra. It is a low surface brightness galaxy that lies in line of sight 4' to the northwest of the more famous planetary nebula M57 Ring Nebula. IC 1296 is much farther away - an estimated distance of ~221-million lightyears as compared to M57's mere 2300LY.

IC 1613 is an irregular dwarf galaxy in the constellation Cetus near the star 26 Ceti. It was discovered in 1906 by Max Wolf, and is approaching Earth at 234 km/s.
IC 1613 is a member of our Local Group. It has played an important role in the calibration of the Cepheid variable period luminosity relation for estimating distances. Other than the Magellanic Clouds, it is the only Local Group dwarf irregular galaxy where RR Lyrae-type variables have been observed.
In 1999, Cole et al. used the Hubble Space Telescope to find that the dominant population of this galaxy has an age of ~7 Gyr. Using its Hess diagram, they found that its evolutionary history may be similar to that of the Pegasus Dwarf Irregular Galaxy. Both galaxies are classified as Ir V in the DDO system. Also in 1999, Antonello et al. found five cepheids of Population II in IC 1613, giving self-evident support for the existence of a very old stellar population component of IC 1613. In 1999, King, Modjaz, & Li discovered the first nova ever detected in IC 1613.

IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe, though it can readily be detected even with binoculars. The dust of the Milky Way makes it difficult to determine the precise distance; modern estimates range from about 7 Mly to about 11 Mly.
IC 342 is one of the brightest two galaxies in the IC 342/Maffei Group of galaxies, one of the galaxy groups that is closest to the Local Group. The galaxy was discovered by William Frederick Denning in 1895. Edwin Hubble first thought it to be in the Local Group, but later it was demonstrated that the galaxy is outside the Local Group.
In 1935, Harlow Shapley declared that this galaxy was the third largest spiral galaxy by angular size then known, smaller only than the Andromeda Galaxy and the Triangulum Galaxy, being wider that the full moon.
It has an H II nucleus.

The Large Magellanic Cloud is a nearby galaxy, and a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs, the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and the putative Canis Major Dwarf Galaxy lying closer to the center of the Milky Way. It has a mass equivalent to approximately 10 billion times the mass of the Sun, making it roughly 1/100 as massive as the Milky Way, and a diameter of about 14,000 light-years. The LMC is the fourth largest galaxy in the Local Group, after the Andromeda Galaxy, the Milky Way, and the Triangulum Galaxy.
While the LMC is often considered an irregular type galaxy, the LMC contains a very prominent bar in its center, suggesting that it may have previously been a barred spiral galaxy. The LMC's irregular appearance is possibly the result of tidal interactions with both the Milky Way and the Small Magellanic Cloud.
It is visible as a faint "cloud" in the night sky of the southern hemisphere straddling the border between the constellations of Dorado and Mensa, and it appears from Earth more than 20 times the width of the full moon.

Leo A is an irregular galaxy that is part of the Local Group. It lies 2.25 million light-years from Earth. This galaxy was discovered by Fritz Zwicky in 1942. The estimated mass of this galaxy is × 10⁷ solar masses, with at least 80% consisting of an unknown dark matter. It is one of the most isolated galaxies in the local group and shows no indications of an interaction or merger for several billion years. The presence of RR Lyrae variables shows that the galaxy has an old stellar population that is up to 10 billion years in age.
The neutral hydrogen in this galaxy occupies in a volume similar to its optical extent, and is distributed in a squashed, uneven ring. The galaxy is not rotating and the hydrogen is moving about in random clumps. The proportion of elements with higher atomic numbers than helium is only about 1-2% of the ratio in the Sun. This indicates a much lower rate of stellar evolution than in the Milky Way galaxy. The Leo A galaxy shows sign of increased star formation some time within the last billion years, although the current level is low. There are four H II regions powered by short-lived, O-class stars.

Leo I is a dwarf spheroidal galaxy in the constellation Leo. At about 820,000 light-years distant, it is a member of the Local Group of galaxies and is thought to be one of the most distant satellites of the Milky Way galaxy. It was discovered in 1950 by Albert George Wilson on photographic plates of the National Geographic Society – Palomar Observatory Sky Survey, which were taken with the 48-inch Schmidt camera at Palomar Observatory.

Leo II is a dwarf spheroidal galaxy about 690,000 light-years away in the constellation Leo. As of October 2008 it is one of 24 known satellite galaxies of the Milky Way. As of 2007 Leo II is thought to have a core radius of 178 ± 13 pc and a tidal radius of 632 ± 32 pc. It was discovered in 1950 by Robert G. Harrington and Albert George Wilson, from the Mount Wilson and Palomar Observatories in California.

Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. Once believed to be a member of the Local Group of galaxies, it is now known to belong to its own group, the IC 342/Maffei Group. It was named after Paolo Maffei, who discovered it and the neighboring Maffei 2 in 1967 via their infrared emissions.
Maffei 1 is a slightly flattened core type elliptical galaxy. It has a boxy shape and is made mainly of old metal-rich stars. It has a tiny blue nucleus in which stars continue to form. Like all large ellipticals it contains a significant population of globular clusters. Maffei 1 is situated at an estimated distance of 3–4 Mpc from the Milky Way. It may be the closest giant elliptical galaxy.
Maffei 1 lies in the Zone of Avoidance and is heavily obscured by the Milky Way's stars and dust. If it were not obscured, it would be one of the largest brightest and best-known galaxies in the sky. It can be observed visually, using a 30–35 cm or bigger telescope under a very dark sky.

Messier 100 is an example of a grand design spiral galaxy located within the southern part of constellation Coma Berenices. It is one of the brightest and largest galaxies in the Virgo cluster, located approximately 55 million light-years distant from Earth and has a diameter of 107,000 light years. It was discovered by Pierre Méchain on March 15, 1781 and was subsequently entered in Messier’s catalogue of nebulae and star clusters after Charles Messier made observations of his own on April 13, 1781. The galaxy was one of the first spirals to be discovered, and was listed as 1 of 14 spiral nebulae by Lord William Parsons of Rosse in 1850. Two satellite galaxies named NGC 4323 -connected with M100 by a bridge of luminous matter- and NGC 4328 are present within this galaxy.

Messier 102 is a galaxy listed in the Messier Catalogue that has not been identified unambiguously. Its original discoverer Pierre Méchain later said that it was a duplicate observation of Messier 101, but there are historical and observational reasons to believe that it could be NGC 5866, although other galaxies have been suggested as possible identities.

Messier 105 is an elliptical galaxy in the constellation Leo.

Messier 106 is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781. M106 is at a distance of about 22 to 25 million light-years away from Earth. It is also a Seyfert II galaxy. Due to x-rays and unusual emission lines detected, it is suspected that part of the galaxy is falling into a supermassive black hole in the center. NGC 4217 is a possible companion galaxy of Messier 106.

Messier 108 is a barred spiral galaxy in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 or 1782. From the perspective of the Earth, this galaxy is seen almost edge-on.
This galaxy is an isolated member of the Ursa Major Cluster of galaxies in the Virgo supercluster. It has a morphological classification of type SBbc in the de Vaucouleurs system, which means it is a barred spiral galaxy with somewhat loosely wound arms. The maximum angular size of the galaxy in the optical band is 11′.1 × 4′.6, and it is inclined 75° to the line of sight.
This galaxy has an estimated mass of 125 billion times the mass of the Sun and includes about 290 ± 80 globular clusters. Examination of the distribution of neutral hydrogen in this galaxy shows shells of expanding gas extending for several kiloparsecs, known as H1 supershells. These may be driven by bursts of star formation activity, resulting in supernovae explosions. Alternatively they may result from an infall of gas from outside the galaxy or by radio jets.
Observations with the Chandra X-ray Observatory have identified 83 X-ray sources, including a source located at the nucleus.

Messier 109 is a barred spiral galaxy approximately 83.5 ± 24 million light-years away in the constellation Ursa Major. M109 can be seen southeast of the star Phecda.

Messier 110 is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy. M110 contains some dust and hints of recent star formation, which is unusual for dwarf elliptical galaxies in general.

Messier 32 is a dwarf elliptical galaxy about 2.65 million light-years away in the constellation Andromeda. M32 is a satellite galaxy of the famous Andromeda Galaxy and was discovered by Le Gentil in 1749. M32 measures only 6.5 ± 0.2 kly in diameter at the widest point. Like most elliptical galaxies, M32 contains mostly older faint red and yellow stars with practically no dust or gas and consequently no current star formation. It does, however, show hints of star formation in the relatively recent past.
The structure and stellar content of M32 is difficult to explain by traditional galaxy formation models. Recent simulations suggest a new scenario in which the strong tidal field of M31 can transform a spiral galaxy into a compact elliptical. As a small spiral galaxy falls into the central parts of M31, most of the outer layers of the smaller spiral are stripped away. The central bulge of the galaxy is much less affected and retains its morphology. Tidal effects trigger a massive star burst in the core, resulting in the high density of M32 we observe today. There is also evidence that M32 has an outer disk.

Messier 49 is an elliptical galaxy located about 56 million light-years away in the equatorial constellation of Virgo. This galaxy was discovered by French astronomer Charles Messier on February 19, 1771. Messier 49 is positioned 4.1° west-southwest of the star Epsilon Virginis.
As an elliptical galaxy, Messier 49 has the physical form of a radio galaxy, but it only has the radio emission of a normal galaxy. From the detected radio emission, the core region is emitting roughly 10⁵³ erg of energy. The nucleus of this galaxy is emitting X-rays, suggests the likely presence of a supermassive black hole with an estimated mass of 5.65 × 10⁸ solar masses, or 565 million times the mass of the Sun. X-ray emissions shows a structure to the north of Messier 49 that resembles a bow shock. To the southwest of the core, the luminous outline of the galaxy can be traced out to a distance of 260 kpc. The only supernova event observed within this galaxy is SN 1969Q, discovered in June 1969.
This galaxy has a large collection of globular clusters, estimated at about 5,900. However, this count is far exceeded by the 13,450 globular clusters orbiting the supergiant elliptical galaxy Messier 87.

Messier 58 is a barred spiral galaxy located within the constellation Virgo, approximately 68 million light-years away from Earth. It was discovered by Charles Messier on April 15, 1779 and is one of four barred spiral galaxies that appear in Messier's catalogue. M58 is one of the brightest galaxies in the Virgo Cluster. From 1779 it was arguably the farthest known astronomical object until the release of the New General Catalogue in the 1880s and even more so the publishing of redshift values in the 1920s.

Messier 59 is an elliptical galaxy in the constellation Virgo.

Messier 60 is an elliptical galaxy approximately 55 million light-years away in the constellation Virgo. It is part of a pair of galaxies known as Arp 116 with NGC 4647.

Messier 61 is a barred spiral galaxy in the Virgo Cluster. It was discovered by Barnabus Oriani on May 5, 1779.

Messier 65 is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo. It was discovered by Charles Messier in 1780. M65, M66, and NGC 3628 comprise the famous Leo Triplet, a small group of galaxies.

Messier 66 is an intermediate spiral galaxy about 36 million light-years away in the constellation Leo. It was discovered by Charles Messier in 1780. M66 is about 95 thousand light-years across with striking dust lanes and bright star clusters along sweeping spiral arms. M66 is part of the famous Leo Triplet, a small group of galaxies that also includes M65 and NGC 3628.

Messier 74 is a face-on spiral galaxy in the constellation Pisces. It is at a distance of about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a Grand Design Spiral Galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. However, the relatively large angular size of the galaxy and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves. It is estimated that M74 is home to about 100 billion stars.

Messier 77 is a barred spiral galaxy about 47 million light-years away in the constellation Cetus. Messier 77 is an active galaxy with an Active Galactic Nucleus, which is obscured from view by astronomical dust at visible wavelengths. The diameter of the molecular disk and hot plasma associated with the obscuring material was first measured at radio wavelengths by the VLBA and VLA. The hot dust around the nucleus was subsequently measured in the mid-infrared by the MIDI instrument at the VLTI. It is the brightest Seyfert galaxy and is of type 2.
Messier 77's diameter is 170,000 light-years.

Messier 81 is a spiral galaxy about 12 million light-years away in the constellation Ursa Major. Due to its proximity to Earth, large size and active galactic nucleus, Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and relatively high brightness also make it a popular target for amateur astronomers.

Messier 82 is a starburst galaxy about 12 million light-years away in the constellation Ursa Major. It is about five times more luminous than the whole Milky Way and one hundred times more luminous than our galaxy's center. The starburst activity is thought to be triggered by interaction with neighboring galaxy M81, and M82 is a member of the M81 Group. As the closest starburst galaxy to our own, M82 is the prototypical example of this type of galaxy. SN 2014J, a Type Ia supernova, was observed in the galaxy on 21 January 2014. In 2014, in studying M82, scientists discovered the brightest pulsar yet known, designated M82 X-2.

Messier 83 is a barred spiral galaxy approximately 15 million light-years away in the constellation Hydra. It is one of the closest and brightest barred spiral galaxies in the sky, making it visible with binoculars. Six supernovae have been observed in M83.

Messier 84 is an elliptical or lenticular galaxy in the constellation Virgo. M84 is situated in the heavily populated inner core of the Virgo Cluster of galaxies.
Radio observations and Hubble Space Telescope images of M84 have revealed two jets of matter shooting out from the galaxy's center as well as a disk of rapidly rotating gas and stars indicating the presence of a 1.5 ×10^9 M☉ supermassive black hole. It also has a few young stars and star clusters, indicating star formation at a very low rate.

Messier 85 is a lenticular galaxy, or elliptical galaxy for other authors, in the Coma Berenices constellation. It is 60 million light years away, and it is estimated to be 125,000 light years across.
It was discovered by Pierre Méchain in 1781. It is the northernmost outlier of the Virgo cluster discovered as of 2004.

Messier 86 is an elliptical or lenticular galaxy in the constellation Virgo. It was discovered by Charles Messier in 1781. M86 lies in the heart of the Virgo Cluster of galaxies and forms a most conspicuous group with another giant, Lenticular Galaxy M84. It displays the highest blue shift of all Messier objects, as it is approaching the Milky Way at 244 km/s. This is due to its falling towards the center of the Virgo cluster from the opposite side, which causes it to move in the direction of the Milky Way.
Messier 86 is linked by several filaments of ionized gas to the severely disrupted spiral galaxy NGC 4438 and shows some gas and interstellar dust that may have been stripped, as well as the gas on those filaments, of it. It's also suffering ram-pressure stripping as it moves at high speed through Virgo's intracluster medium, losing its interstellar medium as it moves through it leaving behind a very long trail of hot gas.
Messier 86 has a rich system of globular clusters, with a total number of around 3,800. Its halo also has a number of stellar streams interpreted as remmants of dwarf galaxies that have been disrupted and absorbed by this galaxy

Messier 87 is a supergiant elliptical galaxy. It was discovered in 1781 by French astronomer Charles Messier, who cataloged it as a nebulous feature. The second brightest galaxy within the northern Virgo Cluster, it is located about 16.4 million parsecs from Earth. Unlike a disk-shaped spiral galaxy, Messier 87 has no distinctive dust lanes and it has an almost featureless, ellipsoidal shape that diminishes in luminosity with distance from the center. At the core is a supermassive black hole, which forms the primary component of an active galactic nucleus. This object is a strong source of multiwavelength radiation, particularly radio waves. A jet of energetic plasma originates at the core and extends outward at least 1,500 parsecs.
The stars in this galaxy form about one sixth of Messier 87's mass. They have a nearly spherically symmetric distribution, while the density of stars decreases with increasing distance from the core. The galactic envelope extends out to a radius of about 150 kpc, where it has been truncated—possibly by an encounter with another galaxy.

Messier 88 is a spiral galaxy about 50 to 60 million light-years away in the constellation Coma Berenices. It was discovered by Charles Messier in 1781.

Messier 89 is an elliptical galaxy in the constellation Virgo. It was discovered by Charles Messier on March 18, 1781. M89 is a member of the Virgo Cluster of galaxies.

Messier 90 is a spiral galaxy about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781.

Messier 91 is a barred spiral galaxy located in the Coma Berenices constellation and is part of the Virgo Cluster of galaxies. M91 is about 63 million light-years away from the earth. It was the last of a group of eight nebulae discovered by Charles Messier in 1781. Originally M91 was a missing Messier object in the catalogue as the result a bookkeeping mistake by Messier. It was not until 1969 that amateur astronomer William C. Williams realized that M91 was NGC 4548, which was documented by William Herschel in 1784

Messier 94 is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier two days later. Although some references describe M94 as a barred spiral galaxy, the "bar" structure appears to be more oval-shaped. The galaxy is also notable in that it has two ring structures.

Messier 95 is a barred spiral galaxy about 38 million light-years away in the constellation Leo. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier four days later. On 16 March 2012, a supernova was discovered in M95.

Messier 96 is an intermediate spiral galaxy about 31 million light-years away in the constellation Leo. It was discovered by French astronomer Pierre Méchain on March 20, 1781. After communicating his finding, French astronomer Charles Messier confirmed the finding four days later and added it to his catalogue of nebulous objects. Finding this object is extremely difficult with binoculars. With a telescope of 25.4 cm aperture, the galaxy is visible as a 3 × 5 arcminute halo with a brighter core region.
This complex galaxy is inclined by an angle of about 53° to the line of sight from the Earth, which is oriented at a position angle of 172°. It is categorized as a double-barred spiral galaxy with a small inner bulge through the core along with an outer bulge. The nucleus displays a weak level of activity of the LINER2 type. Variations in ultraviolet emission from the core suggest the presence of a supermassive black hole. Estimates for the mass of this object range from 1.5×10^6 to 4.8×10^7 times the mass of the Sun.
On May 9, 1998 a supernova event was observed in this galaxy. Designated SN 1998bu, this was a Type Ia supernova explosion.

Messier 98, also known as M98 or NGC 4192, is an intermediate spiral galaxy located about 44.4 million light-years away in the constellation Coma Berenices, about 6° to the east of the bright star Denebola. It was discovered by French astronomer Pierre Méchain on 15 March 1781, along with nearby M99 and M100, and was cataloged by French astronomer Charles Messier on 13 April 1781 in his Catalogue des Nébuleuses & des amas d'Étoiles. Messier 98 has a blue shift and is approaching us at about 140 km per second.
The morphological classification of this galaxy is SABab, which indicates it is a spiral galaxy that displays mixed barred and non-barred features with intermediate to tightly-wound arms and no ring. It is highly inclined to the line of sight at an angle of 74° and has a maximum rotation velocity of 236 km/s. The combined mass of the stars in this galaxy is an estimated 76 billion times the mass of the Sun. It contains about 4.3 billion solar masses of neutral hydrogen and 85 million solar masses in dust. The nucleus is active, displaying characteristics of a "transition" type object.

Messier 99 is an unbarred spiral galaxy approximately 50 million light-years away in the constellation Coma Berenices.

NGC 4676, or the Mice Galaxies, are two spiral galaxies in the constellation Coma Berenices. About 290 million light-years away, they began the process of colliding and merging about 290 million years ago. Their name refers to the long tails produced by tidal action—the relative difference between gravitational pulls on the near and far parts of each galaxy—known here as a galactic tide. Members of the Coma cluster, it is a possibility that both galaxies have experienced collision, and will continue colliding until they coalesce.
The colors of the galaxy are peculiar. In the upper galaxy, a core with some dark markings is surrounded by a bluish white remnant of spiral arms. The tail is unusual, starting out blue and terminating in a more yellowish color, despite the fact that the beginning of each arm in virtually every spiral galaxy starts yellow and terminates in a bluish color. The lower galaxy is closer to normal, with a yellowish core and two arcs; arm remnants underneath are bluish as well.
The galaxies were photographed in 2002 by the Hubble Space Telescope.

The Milky Way is the galaxy that contains our Solar System. Its name “milky” is derived from its appearance as a dim glowing band arching across the night sky in which the naked eye cannot distinguish individual stars. The term “Milky Way” is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος. From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Up until the early 1920s, most astronomers thought that all of the stars in the universe were contained inside of the Milky Way. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble definitively showed that the Milky Way is just one of many billions of galaxies.
The Milky Way is a barred spiral galaxy some 100,000–120,000 light-years in diameter, which contains 100–400 billion stars. It may contain at least as many planets as well.

NGC 1 is a spiral galaxy SbbPa Ring located 190 million light-years away in the constellation Pegasus. At about 90,000 light-years in diameter, it is just a little smaller than our galaxy, the Milky Way. It is the first object listed in the New General Catalogue. In the coordinates used at the time of the catalog's compilation, this object had the lowest right ascension of all the objects in the catalog, making it the first object to be listed when the objects were arranged by right ascension. Since then, the coordinates have shifted, and this object no longer has the lowest right ascension of all the NGC objects.

NGC 1023 is a barred spiral galaxy and a member of the NGC 1023 group of galaxies in the Local Supercluster. Distance measurements vary from 9.3 to 19.7 million parsecs.

NGC 1055 is an edge-on spiral galaxy located in the constellation Cetus that has a prominent nuclear bulge crossed by a wide, knotty, dark lane of dust and gas. The spiral arm structure appears to be elevated above the galaxy's plane and obscures the upper half of the bulge. Discovered on December 19, 1783 by William Herschel from his home in Slough England.
It is a binary system together with the bright spiral galaxy M77. These two are the largest galaxies of a small galaxy group that also includes NGC 1073, and five other small irregular galaxies.
NGC 1087, NGC 1090, and NGC 1094 appear close, but they simply appear in the field of view and are background galaxies.
Based on the published red shift, a rough distance estimate for NGC 1055 is 52 million light-years, with a diameter of about 115,800 light-years. The separation between NGC 1055 and M77 is about 442,000 light-years.
NGC 1055 is a bright infrared and radio source, particularly in the wavelength for warm carbon monoxide. Astronomers believe that this results from unusually active star formation. It most likely has a transitional nucleus, however, there is a small chance that it could be a LINER.

NGC 1073 is a barred spiral galaxy in the constellation Cetus. It probably has a H II nucleus.

NGC 1097 is a barred spiral galaxy about 45 million light-years away in the constellation Fornax. It was discovered by William Herschel on 9 October 1790. Three supernovae have been observed in NGC 1097.
NGC 1097 is also a Seyfert galaxy. Deep photographs revealed four narrow optical jets that appear to emanate from the nucleus. These have been interpreted as manifestations of the active nucleus. Subsequent analysis of the brightest jet's radio-to-X-ray spectral energy distribution were able to rule out synchrotron and thermal free-free emission. The optical jets are in fact composed of stars. The failure to detect atomic hydrogen gas in the jets using deep 21 cm HI imaging with the Very Large Array radio telescope and numerical simulations led to the current interpretation that the jets are actually the shattered remains of a cannibalized dwarf galaxy.
Like most massive galaxies, NGC 1097 has a supermassive black hole at its center. Around the central black hole is a ring of star-forming regions with a network of gas and dust that spirals from the ring to the black hole.

NGC 1232 is an intermediate spiral galaxy about 60 million light-years away in the constellation Eridanus.
It is dominated by millions of bright stars and dark dust, in spiral arms rotating about the center. Open clusters containing bright blue stars are sprinkled along these spiral arms, with dark lanes of dense interstellar dust between. Less visible are dim normal stars and interstellar gas, producing such high mass that they dominate the dynamics of the inner galaxy. Not visible is matter of unknown form called dark matter, needed to explain the motions of the visible material in the outer galaxy.
NGC 1232 and its satellite are part of the Eridanus cluster of galaxies, along with NGC 1300.

NGC 1275 is a type 1.5 Seyfert galaxy located around 237 million light-years away in the direction of the constellation Perseus. NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the center of the large Perseus Cluster of galaxies.

NGC 1291, also known as NGC 1269, is a ring galaxy with an unusual inner bar and outer ring structure located about 33 million light-years away in the constellation Eridanus. It was discovered by James Dunlop in 1826 and subsequently entered into the New General Catalogue as NGC 1291 by Johan Ludvig Emil Dreyer. John Herschel then observed the same object in 1836 and entered it into the catalog as NGC 1269 without realizing that it was a duplicate. This galaxy was cited as an example of a "transitional galaxy" by NASA's Galaxy Evolution Explorer team in 2007.

NGC 1300 is a barred spiral galaxy about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across; just slightly larger than our own galaxy, the Milky Way. It is a member of the Eridanus Cluster, a cluster of 200 galaxies. It was discovered by John Frederick William Herschel in 1835.

NGC 1309 is a spiral galaxy located approximately 120 million light-years away in the constellation Eridanus. It is about 75,000 light-years across; about 3/4s the width of our own galaxy, the Milky Way. Its shape is classified as SAbc, meaning that it has moderately wound spiral arms and no ring. Bright blue areas of star formation can be seen in the spiral arms, while the yellowish central nucleus contains older-population stars. NGC 1309 is one of over 200 members of the Eridanus Group of galaxies.

NGC 1316 is a lenticular galaxy about 60 million light-years away in the constellation Fornax. NGC 1316 is a radio galaxy. It is the fourth-brightest radio source in the sky.

NGC 1365, also known as the Great Barred Spiral Galaxy, is a barred spiral galaxy about 56 million light-years away in the constellation Fornax. The core is an oval shape with an apparent size of about 50″ × 40″. The spiral arms extend in a wide curve north and south from the ends of the east-west bar and form an almost ring like Z-shaped halo. The central mass in active galactic nucleus rotate close to relativistic limit.
Supernovae 2012fr, 2001du, 1983V, and 1957C were observed in NGC 1365.
In February 2013, observations using the NuSTAR satellite have found out that the central supermassive black hole of NGC 1365, measured to be about 2 million solar masses in mass, is spinning at almost the speed of light
NGC 1365's central region showing dust lanes.
Play media
This video sequence shows the rapid brightening and slower fading of a supernova explosion in the galaxy.
The Great Barred Spiral Galaxy.
Credit: ESO/IDA/Danish 1.5 m/ R. Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron..
An ultraviolet image of NGC 1365 taken with GALEX.
Credit: GALEX/NASA.
HAWK-I infrared image of the barred spiral galaxy NGC 1365.
Credit: ESO/P. Grosbøl.

NGC 1427A is an irregular galaxy in the constellation Eridanus. Its distance modulus has been estimated using the globular cluster luminosity function to be 31.01 ± 0.21 which is about 52 Mly. It is the brightest dwarf irregular member of the Fornax cluster and is in the foreground of the cluster's central galaxy NGC 1399.

NGC 147 is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy. It forms a physical pair with the nearby galaxy NGC 185, another remote satellite of M31. It was discovered by John Herschel in September 1829. Visually it is both fainter and slightly larger than NGC 185. This means that NGC 147 is more difficult to see than NGC 185, which is visible in small telescopes. In the Webb Society Deep-Sky Observer's Handbook, the visual appearance of NGC 147 is described as follows:
Large, quite faint, irregularly round; it brightens in the middle to a stellar nucleus.
The membership of NGC 147 in the Local Group was confirmed by Walter Baade in 1944 when he was able to resolve the galaxy into individual stars with the 100-inch telescope at Mount Wilson near Los Angeles.

NGC 1512 is a barred spiral galaxy approximately 30 million light-years away from Earth in the constellation Horologium. It is a member of the Dorado Group.

NGC 1566 is an intermediate spiral galaxy in the constellation Dorado. It is the dominant member of the Dorado Group and also its brightest member. It is one of the brightest Seyfert galaxies in the sky. Its absolute luminosity is 3.7×10^10 L☉. It contains 1.4×10^10 M☉ of H I.

NGC 1569 is a dwarf irregular galaxy in Camelopardalis. While this faint galaxy is not a popular amateur astronomy target, it is well studied by professional astronomers, who are interested in the history of star formation within the galaxy. The galaxy is relatively nearby. Consequently, the Hubble Space Telescope can easily resolve the stars within the galaxy. The distance to the galaxy was previously believed to be only 2.4 Mpc. However, in 2008 scientists studying images from Hubble calculated the galaxy's distance at nearly 11 million light-years away, about 4 million light-years farther than previous thought and making it a member of the IC 342 group of galaxies.

NGC 1672 is a barred spiral galaxy located in the constellation Dorado. It was originally thought to be a member of the Dorado Group, however, this membership was later rejected. NGC 1672 has a large bar which is estimated to measure around 20 kpc. It has very strong radio emissions emanating from its nucleus, bar, and the inner portion of the spiral arm region. The nucleus is Seyfert type 2 and is engulfed by a starburst region. The strongest polarized emissions come from the northeastern region which is upstream from its dust lanes. Magnetic field lines are at large angles with respect to the bar and turn smoothly to the center.

NGC 1808 is a Seyfert galaxy located in the constellation Columba. Supernova 1993 af went off in NGC 1808.

NGC 185 is a dwarf spheroidal galaxy about 2.08 million light-years away in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy. NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters. NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus and is usually classified as a type 2 Seyfert galaxy, though its status as a Seyfert is questioned. It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.

NGC 2 is a spiral galaxy in the constellation Pegasus. It lies slightly to the south of NGC 1. It is a faint spiral galaxy of apparent magnitude 14.2.

NGC 20 is a lenticular galaxy located in the Andromeda constellation.

NGC 2403 is an intermediate spiral galaxy in the constellation Camelopardalis. NGC 2403 is an outlying member of the M81 Group, and is approximately 8 million light-years distant. It bears a striking similarity to M33, being about 50,000 light years in diameter and containing numerous star-forming H II regions. The northern spiral arm connects it to nearby galaxy NGC 2404. NGC 2403 can be observed using 10×50 binoculars.

NGC 247 is an intermediate spiral galaxy about 11.1 Mly away in the constellation Cetus. This distance was confirmed in late February 2011. Previous measurements showed that the galaxy was about 12.2 Mly away, but this was proved to be wrong. NGC 247 is a member of the Sculptor Group.
NGC 247 is marred by an unusually large void on one side of its spiral disk. This void contains some older, redder stars but no younger, bluer stars.

NGC 25 is a lenticular galaxy situated in the Phoenix constellation.

NGC 2683 is a spiral galaxy discovered by William Herschel on February 5, 1788. It was nicknamed the "UFO Galaxy" by the Astronaut Memorial Planetarium and Observatory. It is viewed nearly edge-on from Earth's location in space and is located between 16 to 25 million light-years away. It is receding from Earth at 410 km/s, and from the Galactic Center at 375 km/s. The reddened light from the center of the galaxy appears yellowish due to the intervening gas and dust located within the outer arms of NGC 2683.

NGC 2775 is a spiral galaxy in the constellation Cancer. This galaxy has a bulge and multiple spiral arms, on which few HII regions can be detected, implying recent star formation. It was discovered by William Herschel in 1783.
NGC 2775 is the most prominent galaxy in a small galaxy group known as NGC 2775 group, part of the Virgo Supercluster, along with our own Local Group. Other members of the NGC 2775 group include NGC 2777 and UGC 4781.
SN1993z is the only supernova known to have occurred in NGC 2775 and was a Type Ia with a peak magnitude of 13.9.

NGC 278 is a spiral galaxy in the constellation Cassiopeia. It has a H II nucleus.

NGC 2787 is a barred lenticular galaxy approximately 24 million light-years away in the constellation Ursa Major. In 1999, the Hubble Space Telescope took a look at NGC 2787.

NGC 2841 is an inclined unbarred spiral galaxy in the constellation Ursa Major. Initially thought to be about 30 million light years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined that it was approximately 14.1 megaparsecs or 46 million light years distant.

NGC 2903 is a barred spiral galaxy about 30 million light-years away in the constellation Leo. It was discovered by William Herschel who cataloged it on November 16, 1784. NGC 2905 is a bright star cloud within this galaxy.

Part of the M81 group, NGC 2976, located 1° 20′ southwest of M81, is an unbarred spiral galaxy. The inner structure contains many dark lanes and stellar condensations in its disk. The galaxy is sometimes classified as Sdp because its spiral arms are difficult to be traced. The bright inner part of this disk appears to have a defined edge. These distortions are results from the gravitational interactions with its neighbors.
NGC 2976 was discovered by William Herschel on November 8, 1801, and cataloged as H I.285.
NGC 2976 by HST.
The outer regions of NGC 2976.

NGC 3 is a lenticular galaxy in the Pisces constellation.

NGC 300 is a spiral galaxy in the constellation Sculptor. It is one of the closest galaxies to the Local Group, and probably lies between us and the Sculptor Group. It is the brightest of the five main spirals in the direction of the Sculptor Group. It is inclined at an angle of 42° when viewed from earth and shares many characteristics of the Triangulum Galaxy.

NGC 3079 is a barred spiral galaxy about 50 million light-years away, and located in the constellation Ursa Major. A prominent feature of this galaxy is the "bubble" forming in the very center.

NGC 3109 is a small Magellanic type spiral or irregular galaxy around 4.2 Mly away in the direction of the constellation of Hydra. It is the most prominent member of a Local Group subgroup. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy, Antlia Dwarf. It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.

NGC 3115 is a lenticular galaxy in the constellation Sextans. The galaxy was discovered by William Herschel on February 22, 1787. At about 32 million light-years away from us it is several times bigger than our Milky Way. It is a lenticular galaxy because it contains a disk and a central bulge of stars, but without a detectable spiral pattern. NGC 3115 is seen almost exactly edge-on, but was nevertheless mis-classified as elliptical. There is some speculation that NGC 3115, in its youth, was a quasar.

NGC 3184 is a spiral galaxy approximately 40 million light-years away in the constellation Ursa Major. It has two HII regions named NGC 3180 and NGC 3181.
NGC 3184 is notable for its high abundance of heavy elements and that was a magnitude 14 Type II supernova detected on December 9, 1999. Other supernovae in NGC 3184 include 1921B, 1921C and 1937F.

NGC 3190 is a spiral galaxy with tightly wound arms and lying in the constellation Leo. It was discovered by William Herschel in 1784. NGC 3190 is member of Hickson 44 galaxy group, estimated at around 80 million light years away, and consisting of four galaxies in a tight group - NGC 3193 is fairly featureless, NGC 3187 is a dim but striking spiral galaxy and NGC 3185 has a barred spiral structure with an outer ring.
In 2002 two supernovae were observed in the galaxy. A Brazilian amateur astronomer Paulo Cacella detected one supernova in the southeastern part in March 2002, and then an Italian team, while studying the first one, detected a second supernova on the other side two months later.
In 2012 Apple Inc used a blue tinted image of NGC 3190 as their desktop image for their release of OS X Mountain Lion.
Spiral Galaxy NGC 3190 as imaged by ESO/VLT in March 2003 (SN 2002bo close-up)
Combined Hubble Legacy images by Robert Gendler.
GALEX ultraviolet image of NGC 3190 field.

NGC 3227 is a spiral galaxy that is interacting with the dwarf elliptical galaxy NGC 3226. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies. Both galaxies may be found in the constellation Leo.
Sir William Herschel already recognised them as a 'double nebula' and they were jointly listed as Holm 187 in the Catalogue of Double and Multiple Galaxies and as Arp 94 in the Atlas of Peculiar Galaxies. Amateur telescopes can discern them but require magnification of about 100 times. They are situated 50′ east of the well-known double star system Gamma Leonis.

NGC 3310 is a grand design spiral galaxy in the constellation Ursa Major. It is a starburst galaxy and it is likely that NGC 3310 collided with one of its satellite galaxies about 100 million years ago, triggering widespread star formation. It is thought to be located approximately 46 million light-years away from the Earth, and is thought to be about 22,000 light-years wide.
The ring clusters of NGC 3310 have been undergoing starburst activity for at least the last 40 million years.

NGC 3314 is a pair of overlapping spiral galaxies between 117 and 140 million light-years away in the constellation Hydra. This unique alignment gives astronomers the opportunity to measure the properties of interstellar dust in the face-on foreground galaxy, which appear dark against the background galaxy. Unlike interacting galaxies, the two components of NGC3314 are physically unrelated.
While searching for overlapping galaxies in April 1999, two astronomers from the University of Alabama were the first to image the deep sky object in enough detail to tell that it was in fact two galaxies. In a March 2000 observation of the galaxies, a prominent green star-like object was seen in one of the arms. Astronomers theorized that it could have been a supernova, but the unique filtering properties of the foreground galaxy made it difficult to decide definitively.

NGC 3370 is a spiral galaxy about 98 million light-years away in the constellation Leo. It is comparable to our own Milky Way both in diameter and mass. NGC 3370 exhibits an intricate spiral arm structure surrounding a poorly defined nucleus.

NGC 3384 is an elliptical galaxy in the constellation Leo. The galaxy was discovered by Herschel in 1784. The high age of the stars in the central region of NGC 3384 was confirmed after analysis of their color. More than 80% were found to be Population II stars which are over a billion years old.

NGC 3521 is a flocculent spiral galaxy located around 26 million light-years away from Earth in the constellation Leo. It has a morphological classification of SABbc, which indicates that it is a spiral galaxy with a trace of a bar structure, a weak inner ring, and moderate to loosely wound arm structure. The bar structure is difficult to discern, both because it has a low ellipticity and the galaxy is at a high inclination of 72.7° to the line of sight. The relatively bright bulge is nearly 3/4 the size of the bar, which may indicate the former is quite massive. The nucleus of this galaxy is classified as an HII LINER, as there is an H II region at the core and the nucleus forms a low-ionization nuclear emission-line region.

NGC 3628, also known as Sarah's Galaxy, is an unbarred spiral galaxy about 35 million light-years away in the constellation Leo. It was discovered by William Herschel in 1784. It has an approximately 300,000 light-years long tidal tail. NGC 3628 along with M65 and M66 form the famous Leo Triplet, a small group of galaxies. Its most conspicuous feature is the broad and obscuring band of dust located along the outer edge of its spiral arms, effectively transecting the galaxy to our view.

NGC 3982 is an intermediate spiral galaxy approximately 68 million light-years away in the constellation Ursa Major. It is also known as UGC 6918. It was discovered by William Herschel on April 14, 1789 and misclassified as planetary nebula. NGC 3982 is a part of the M109 Group.
At an apparent magnitude of 12.0, NGC 3982 needs a telescope to be viewed. Using small telescopes, the galaxy appears as a very faint, diffuse patch of light with its central region appearing as a slightly brighter diffuse ball.

NGC 4013 is an edge-on barred spiral galaxy about 55 million light-years away in the constellation Ursa Major. The disk of NGC 4013 shows a distinct "peanut"-shaped bulge in long exposure photographs that N-body computer simulations suggest is consistent with a stellar bar seen perpendicular to the line of sight.
A recent deep color image of NGC 4013 revealed a looping tidal stream of stars extending over 80 thousand light-years from the Galactic Center. This structure is thought to be the remnants of a smaller galaxy that was torn apart by tidal forces as it collided with NGC 4013.
Supernova SN 1989Z was discovered on December 30, 1989 at apparent magnitude 12.

NGC 404 is a galaxy located about 10 million light years away in the constellation Andromeda. It was discovered by William Herschel in 1784, and is visible through small telescopes. NGC 404 lies just beyond the Local Group and does not appear gravitationally bound to it. It is notable for being within 7 arc-minutes of second magnitude star Mirach, making it a difficult target to observe or photograph and granting it the nickname "Mirach's Ghost".

NGC 4151 is an intermediate spiral Seyfert galaxy located 19 megaparsecs from Earth in the constellation Canes Venatici. The galaxy was first mentioned by William Herschel on March 17, 1787; it was one of the two Seyfert galaxies described in the paper which defined the term. It is one of the nearest galaxies to Earth to contain an actively growing supermassive black hole; it was speculated that the nucleus may host a binary black hole, with about 40 million and about 10 million solar masses respectively, orbiting with a 15.8-year period. This is, however, still a matter of active debate.
Some astronomers nickname it the "Eye of Sauron" from its appearance.

NGC 4214 is a dwarf barred irregular galaxy located around 10 million light-years away in the constellation Canes Venatici.

NGC 4236 is a barred spiral galaxy located in the constellation Draco.

NGC 4244, also Caldwell 26, is an edge-on loose Spiral galaxy and Caldwell object in the constellation Canes Venatici. It is part of the M94 Group, a galaxy group relatively close to the Local Group containing the Milky Way. It shines at magnitude +10.2/+10.6. Its celestial cooridinates are RA 12ʰ 17.5ᵐ, dec +37° 49′. It is located near a naked-eye G-class star Beta Canum Venaticorum, barred spiral galaxy NGC 4151, and irregular galaxy NGC 4214. The galaxy lies approximately 6.5 million/14 million light years away, with a redshift of +243/493 km/s. A nuclear star cluster and halo is located at the centre of this galaxy.

NGC 4261 is an elliptical galaxy located behind the Virgo Cluster in the W-cloud.
The active galactic nucleus contains a 400 million solar mass supermassive black hole with an 800 light-year-wide spiral-shaped disk of dust fueling it.
The galaxy is estimated to be about 60 thousand light-years across, and the jet is estimated to span about 88 thousand light-years.

NGC 4314 is a barred spiral galaxy approximately 40 million light-years away in the constellation Coma Berenices. Perhaps the most prominent and unusual feature is its "nuclear starbust ring" of bright young stars. These rings are thought to be due in part to Lindblad resonance. It is thought that this explosion of star formation has occurred over the past few millions of years. This time frame is remarkably short in astronomical terms because most main sequence stars have lifetimes of billions of years and their birth is not usually uniform throughout a galaxy. Further study will be required to understand more about the evolution of such ring structures in galaxies.

NGC 4319 is a face-on barred spiral galaxy located about 77 million light years away in the constellation Draco. The morphological classification is SBab, which indicates it is a barred spiral with an inner ring structure and moderate to tightly wound arms. It is situated in physical proximity to the galaxies NGC 4291 and NGC 4386, with X-ray emissions from the intervening gap indicating NGC 4319 and NGC 4291 may be interacting. NGC 4319 has a much higher proportion of ionized hydrogen compared to the Milky Way galaxy.
In 1971, American astronomer Halton Arp noted what appeared to be a physical connection between NGC 4319 and Markarian 205, a quasi-stellar object with a much higher redshift. He suggested that if Markarian 205 is not an accidentally projected background object, then it may instead have been ejected from the nucleus of this galaxy. The discovery of an apparent luminous connection between the two created a storm of controversy as astronomers sought to refute the assertion and provide other explanations.

NGC 4395 is a low surface brightness spiral galaxy with a halo that is about 8′ in diameter. It has several wide areas of greater brightness running northwest to southeast. The one furthest southeast is the brightest. Three of the patches have their own NGC numbers: 4401, 4400, and 4399 running east to west.
The nucleus of NGC 4395 is active and the galaxy is classified as a Seyfert. It is notable for containing one of the smallest supermassive black hole with an accurately-determined mass. The central black hole has a mass of "only" 300,000 sun masses, which would make it a so-called "intermediate-mass black hole".

NGC 4414 is an unbarred spiral galaxy about 62 million light-years away in the constellation Coma Berenices. It is a flocculent galaxy, with short segments of spiral structure but without the dramatic well-defined spiral arms of a grand design spiral. In 1974 a supernova, SN 1974G, was observed and was the only supernova in this galaxy to be recorded until June 7, 2013 when SN 2013df was discovered at Magnitude 14.
It was imaged by the Hubble Space Telescope in 1995, as part of the HST's main mission to determine the distance to galaxies, and again in 1999 as part of the Hubble Heritage project. It has been part of an ongoing effort to study its Cepheid variable stars. The outer arms appear blue due to the continuing formation of young stars and include a possible Luminous Blue Variable with an absolute magnitude of −10
NGC 4414 is also a very isolated galaxy without signs of past interactions with other galaxies and despite not being a starburst galaxy shows a high density and richness of gas -both atomic and molecular, with the former extending far beyond its optical disk-

NGC 4449 is an irregular galaxy in the constellation Canes Venatici. It is located about 12 million light-years away, part of the M94 Group, a galaxy group relatively close to the Local Group containing the Milky Way.

NGC 45 is a low surface brightness spiral galaxy in the constellation of Cetus. It was discovered on 11 November 1835 by the English astronomer John Herschel. In the sky, it is located near the magnitude 6.8 star HD 941.

NGC 4526 is a lenticular galaxy in the Virgo constellation that is seen nearly edge-on. The morphological classification is SAB0°, which indicates a lenticular structure with a weak bar across the center and pure spiral arms without a ring. It belongs to the Virgo cluster and is one of the brightest known lenticular galaxies. The inner nucleus of this galaxy displays a rise in stellar orbital motion that indicates the presence of a central dark mass. The best fit model for the motion of molecular gas in the core region suggests there is a supermassive black hole with about 4.5+4.2
−3.0 × 10⁸ times the mass of the Sun. This is the first object to have its black-hole mass estimated by measuring the rotation of gas molecules around its centre with an Astronomical interferometer.
Supernova SN 1969E was discovered in this galaxy in 1969, reaching a peak magnitude of 16. In 1994, a Type 1a supernova was discovered about two weeks before reaching peak brightness. Designated SN 1994D, it was caused by the explosion of a white dwarf star composed of carbon and oxygen.

NGC 4555 is a solitary elliptical galaxy about 40,000 parsecs across, and about 310 million light years distant. Observations by the Chandra X-ray Observatory have shown it to be surrounded by a halo of hot gas about 120,000 parsecs across. The hot gas has a temperature of around 10,000,000 kelvins. The galaxy is one of the few elliptical galaxies proven to have significant amounts of dark matter. Large amounts of dark matter are necessary to prevent the gas from escaping the galaxy; the visible mass clearly is not large enough to hold such an extensive gas halo. The dark matter halo is estimated to have 10 times the mass of the stars in the galaxy.
NGC 4555 is important because of its isolation. Most elliptical galaxies are found in the cores of groups and clusters of galaxies, and almost all those for which dark matter estimates are available are located in the centres of these larger systems. In these circumstances it impossible to know whether the dark matter is associated with the galaxy or the surrounding cluster.

NGC 4559 is a spiral galaxy in the constellation Coma Berenices. Distance estimates for NCG 4559 range from about 29 million light-years to 51 million light-years, averaging about 29 million light-years.

NGC 4565 is an edge-on spiral galaxy about 30 to 50 million light-years away in the constellation Coma Berenices.
The 10th magnitude galaxy sits perpendicular to our own Milky Way galaxy and is almost directly above the North Galactic Pole.
It is known as the Needle Galaxy for its narrow profile. First spotted in 1785 by Sir William Herschel, this is one of the most famous examples of an edge-on spiral galaxy. "Visible through a small telescope, some sky enthusiasts consider NGC 4565 to be a prominent celestial masterpiece Messier missed."

NGC 4622 is a face-on spiral galaxy located in the constellation Centaurus.

NGC 4631 is an edge-on spiral galaxy in the constellation Canes Venatici. This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, hence its nickname. Because this nearby galaxy is seen edge-on from Earth, professional astronomers observe this galaxy to better understand the gas and stars located outside the plane of the galaxy.

NGC 4725 is an intermediate barred spiral galaxy about 40 million light-years away in the constellation Coma Berenices. NGC 4725 is a Seyfert Galaxy, suggesting an active galactic nucleus containing a supermassive black hole.

NGC 4889, also known as Caldwell 35, is a supergiant class-4 elliptical galaxy, the brightest within the Coma Cluster and a Caldwell object in the constellation Coma Berenices. It shines at magnitude +11.4. Its celestial coordinates are RA 13h00.1m, DEC +27°59'. It is located near the G-class naked-eye star Beta Comae Berenices, the galaxy NGC 4874, and the North Galactic Pole. It lies roughly 308 million light-years away. The main cluster is retreating at roughly 7,000 kilometres per second, while NGC 4889 itself is retreating at 6,495 kilometres per second.
As of December 2011, NGC 4889 harbors one of the largest observed black holes to date, with a mass estimated at 21 billion solar masses. This is the best fit; the possible range of masses is from 6 billion to 37 billion M☉.

NGC 4921 is a barred spiral galaxy in the Coma Cluster, located in the constellation Coma Berenices. It is about 320 million light-years from Earth. The galaxy has a nucleus with a bar structure that is surrounded by a distinct ring of dust that contains recently formed, hot blue stars. The outer part consists of unusually smooth, poorly distinguished spiral arms.
In 1976, Canadian astronomer Sidney Van den Bergh categorized this galaxy as "anemic" because of the low rate at which stars are being formed. He noted that it has "an unusually low surface brightness and exhibits remarkably diffuse spiral arms". Nonetheless, it is the brightest spiral galaxy in the coma cluster. This galaxy is located near the center of the cluster and has a high relative velocity compared to the mean cluster velocity. When examined at the 21 cm wavelength Hydrogen line, NGC 4921 was found to be strongly H I deficient, indicating it is low in hydrogen. The distribution of hydrogen has also been deeply perturbed toward the SE spiral arm and is less extended than the optical disk of the galaxy. This may have been caused by interaction with the intergalactic medium, which is stripping off the gas.

NGC 4945 is a spiral galaxy in the constellation Centaurus, and near the bright star, Zeta Centauri. The galaxy was discovered by James Dunlop in 1826. It is thought to be similar to the Milky Way Galaxy, although X-ray observations show that NGC 4945 has an unusual energetic Seyfert 2 nucleus that might house a large black hole.

NGC 5005 is an inclined spiral galaxy in the constellation Canes Venatici. The galaxy has a relatively bright nucleus and a bright disk that contains multiple dust lanes. The galaxy's high surface brightness makes it an object that is visible to amateur astronomers using large amateur telescopes.
Distance measurements for NGC 5005 vary from 13.7 megaparsecs to 34.6 megaparsecs, averaging about 20 megaparsecs.

NGC 5033 is an inclined spiral galaxy located in the constellation Canes Venatici. Distance estimates vary from between 38 to 60 million light years from the Milky Way Galaxy. The galaxy has a very bright nucleus and a relatively faint disk. Significant warping is visible in the southern half of the disk. The galaxy's relatively large angular size and relatively high surface brightness make it an object that can be viewed and imaged by amateur astronomers. The galaxy's location relatively near Earth and its active galactic nucleus make it a commonly studied object for professional astronomers.

NGC 5195 is a dwarf galaxy that is interacting with the Whirlpool Galaxy. Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most famous interacting galaxy pairs.

NGC 520 is a pair of colliding spiral galaxies about 90 million light-years away in the constellation Pisces. It has a H II nucleus.

NGC 5248 is a compact intermediate spiral galaxy about 59 million light-years away in the constellation Boötes. It is a member of the NGC 5248 Group of galaxies, itself one of the Virgo III Groups strung out to the east of the Virgo Supercluster of galaxies. Distance measurements to NGC 5248 vary from 41.4 million light-years to 74.0 million light-years, averaging about 58.7 million light-years.

NGC 5474 is a peculiar dwarf galaxy in the constellation Ursa Major. It is one of several companion galaxies of the Pinwheel Galaxy, a grand-design spiral galaxy. Among the Pinwheel Galaxy's companions, this galaxy is the closest to the Pinwheel Galaxy itself. The gravitational interaction between NGC 5474 and the Pinwheel Galaxy have strongly distorted the galaxy. As a result, the disk is offset relative to the nucleus. The star formation in this galaxy is also offset from the nucleus. NGC 5474 shows some signs of a spiral structure. As a result, this galaxy is often classified as a dwarf spiral galaxy, a relative rare group of dwarf galaxies.

NGC 55 is a Magellanic type barred spiral galaxy located about 7 million light-years away in the constellation Sculptor. Along with its neighbor NGC 300, it is one of the closest galaxies to the Local Group, probably lying between us and the Sculptor Group.

NGC 5866 is a relatively bright lenticular or spiral galaxy in the constellation Draco. NGC 5866 was probably discovered by Pierre Méchain or Charles Messier in 1781, and independently found by William Herschel in 1788.

NGC 5907 is a spiral galaxy located approximately 50 million light years from Earth. It has an anomalously low metallicity and few detectable giant stars, being apparently composed almost entirely of dwarf stars. It is a member of the NGC 5866 Group.
NGC 5907 has long been considered a prototypical example of a warped spiral in relative isolation. Then in 2006, an international team of astronomers announced the presence of an extended tidal stream surrounding the galaxy that challenges this picture and suggests the gravitational perturbations induced by the stream progenitor may be the cause for the warp.
NGC 5907 is also known at the Knife Edge or Splinter galaxy.
The galaxy was discovered in 1788 by William Herschel. Supernova 1940A was in this galaxy.

NGC 6240 is a well-studied nearby ultraluminous infrared galaxy in the constellation Ophiuchus. The galaxy is the remnant of a merger between two smaller galaxies. The collision between the two progenitor galaxies has resulted in a single larger galaxy with two distinct nuclei and a highly disturbed structure, including faint extensions and loops.

NGC 6744 is an intermediate spiral galaxy about 30 million light-years away in the constellation Pavo. It is considered one of the most Milky Way-like spiral galaxies in our immediate vicinity, with flocculent arms and an elongated core. It also has at least one distorted companion galaxy superficially similar to one of the Magellanic Clouds. A supernova was discovered in the galaxy in 2005.

NGC 6745 is an irregular galaxy about 206 million light-years away in the constellation Lyra. It is actually a triplet of galaxies in the process of colliding.
The three galaxies have been colliding for hundreds of millions of years. After passing through the larger galaxy, the smaller one is now moving away. The larger galaxy was probably a spiral galaxy before the collision, but was damaged and now appears peculiar. It is unlikely that any stars in the two galaxies collided directly because of the vast distances between them. The gas, dust, and ambient magnetic fields of the galaxies, however, do interact directly in a collision. As a result of this interaction, the smaller galaxy has probably lost most of its interstellar medium to the larger one.
The age of NGC 6745 is estimated to be ~10 Myr.
A part of an image on NGC 6745 was found in the keylogger part of the Duqu malware, for unknown reason.

NGC 6822 is a barred irregular galaxy approximately 1.6 million light-years away in the constellation Sagittarius. Part of the Local Group of galaxies, it was discovered by E. E. Barnard in 1884, with a six-inch refractor telescope. It is one of the closer galaxies to the Milky Way. It is similar in structure and composition to the Small Magellanic Cloud. It is about 7,000 light-years in diameter.

NGC 6946, is an intermediate spiral galaxy about 22.5 million light-years away, in the constellations Cepheus and Cygnus. It was discovered by William Herschel on September 9, 1798. NGC 6946 is highly obscured by interstellar matter of the Milky Way galaxy, as it is quite close to the galactic plane. Nine supernovae in the last 60 years or so, have been observed in NGC 6946.
There are polarisation data within ranges 0.17-0.18 m and 0.21-0.23 m, observed in 2003 by WSRT.

NGC 7049 is a galaxy that spans about 150 000 light-years and lies about 100 million light-years away from Earth in the inconspicuous southern constellation of Indus.
NGC 7049's unusual appearance is largely due to a prominent rope-like dust ring which stands out against the starlight behind it. These dust lanes are usually seen in young galaxies with active star-forming regions. NGC 7049 shows the features of both an elliptical galaxy and a spiral galaxy, and has relatively few globular clusters. The bright star at the top of the ring is in our own Galaxy. Not visible is an unusual central polar ring of gas circling out of the plane near the galaxy's center. NGC 7049 is the brightest of the Indus triplet of galaxies, and its structure might have arisen from several recent galaxy collisions. Typical BCGs are some of the oldest and most massive galaxies.

NGC 7217 is an unbarred spiral galaxy in the constellation Pegasus.

NGC 7252 is a peculiar galaxy resulting from an interaction between two galaxies that started a billion years ago. It is located 220 million light years away in the constellation Aquarius. It is also called Atoms for Peace galaxy, a nickname which comes from its loop-like structure, made of stars, that resembles a diagram of an electron orbiting an atomic nucleus.

NGC 7318 are a pair of colliding galaxies about 300 million light-years away in the Constellation Pegasus. They are members of the famous Stephan's Quintet.
The Spitzer Space Telescope revealed the presence of a huge intergalactic shock wave, shown by the magnificent green arc in the picture at right produced by one galaxy falling into another at millions of miles per hour. As NGC 7318B collides with NGC 7318A, gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow. The molecular hydrogen seen here is one of the most turbulent forms of molecular hydrogen ever seen. This phenomenon was discovered by an international team of scientists of the Max Planck Institute for Nuclear Physics in Heidelberg. Most notable is the fact that this collision can help provide a view into what happened in the early universe 10 billion years ago when it formed.

NGC 7319 is a spiral galaxy member of the Stephan's Quintet located in the constellation Pegasus.

NGC 7320 is a spiral galaxy in the Stephan's Quintet. However, it is not an actual member of the galaxy group, but a much closer line-of-sight galaxy at a distance of about 40 million light years. Other galaxies of Stephan's Quintet are some 300 million ly distant.

NGC 7331 is a spiral galaxy about 40 megalight-years away in the constellation Pegasus. It was discovered by William Herschel in 1784. NGC 7331 is the brightest member of the NGC 7331 Group of galaxies.
The galaxy is similar in size and structure to the galaxy we inhabit, and is often referred to as "the Milky Way's twin", although recent discoveries regarding the structure of the Milky Way may call this similarity into doubt.

NGC 7424 is a barred spiral galaxy located 37.5 million light-years away in the southern constellation Grus. Its structure and diameter make it similar to our own galaxy, the Milky Way. It is called a "grand design" galaxy because of its well defined spiral arms. One supernova and two ultraluminous X-ray sources have been discovered in NGC 7424.

NGC 7479 is a barred spiral galaxy about 105 million light-years away in the constellation Pegasus. It was discovered by William Herschel in 1784. Supernovae SN 1990U and SN2009jf occurred in NGC 7479. NGC 7479 is also recognized as a Seyfert galaxy undergoing starburst activity in the nucleus and the outer arms. Polarization studies of this galaxy indicate that it recently underwent a minor merger and that it is unique in the radio continuum, with arms opening in a direction opposite to the optical arms.

NGC 772 is an unbarred spiral galaxy approximately 130 million light-years away in the constellation Aries.

NGC 7742 is a face-on unbarred spiral galaxy in the constellation Pegasus.
The galaxy is unusual in that it contains a ring but no bar. Typically, bars are needed to produce a ring structure. The bars' gravitational forces move gas to the ends of the bars, where it forms into the rings seen in many barred spiral galaxies. In this galaxy, however, no bar is present, so this mechanism cannot be used to explain the formation of the ring. O. K. Sil'chenko and A. V. Moiseev proposed that the ring was formed partly as the result of a merger event in which a smaller gas-rich dwarf galaxy collided with NGC 7742. As evidence for this, they point to the unusually bright central region, the presence of highly inclined central gas disk, and the presence of gas that is counterrotating with respect to the stars.

NGC 7793 is a spiral galaxy about 12.7 million light-years away in the constellation Sculptor. It was discovered in 1826 by James Dunlop.

NGC 7814 is a spiral galaxy about 40 million light-years away in the constellation Pegasus. The galaxy is seen edge-on from Earth. It is sometimes referred to as "the little sombrero", a miniature version of Messier 104. The star field behind NGC 7814 is known for its density of faint, remote galaxies as can be seen in the image here – in the same vein as the Hubble Deep Field.

NGC 891 is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus.
The object is visible in small to moderate size telescopes as a faint elongated smear of light with a dust lane visible in larger apertures.
In 1999, the Hubble Space Telescope imaged NGC 891 in infrared.
In 2005, due to its attractiveness and scientific interest, NGC 891 was selected to be the first light image of the Large Binocular Telescope. In 2012, it was again used as a first light image of the Discovery Channel Telescope with the Large Monolithic Imager.
Supernova SN 1986J was discovered on August 21, 1986 at apparent magnitude 14.

NGC 925 is a barred spiral galaxy located about 30 million light-years away in the constellation Triangulum. The morphological classification of this galaxy is SBd, which indicates that this has a bar structure and loosely wound spiral arms with no ring. The spiral arm to the south is stronger than the northern arm, with the latter appearing flocculent and less coherent. The bar is offset from the center of the galaxy and is the site of star formation all along its length. Both of these morphological traits—a dominant spiral arm and the offset bar—are typically characteristics of a Magellanic spiral galaxy. The galaxy is inclined at an angle of 55° to the line of sight along a position angle of 102°.
This galaxy is a member of the NGC 1023 Group, a nearby, gravitationally-bound group of galaxies associated with NGC 1023. However, the nearest member lies at least 650 kly distant from NGC 925. There is a 10 million solar mass cloud of neutral hydrogen attached to NGC 925 by a streamer. It is uncertain whether this is a satellite dwarf galaxy, the remnant of a past tidal interaction, or a cloud of primordial gas.

The Pegasus Dwarf Irregular Galaxy is a dwarf irregular galaxy in the direction of the constellation Pegasus. It was discovered by A.G. Wilson in the 1950s. The Pegasus Dwarf is a companion of the Andromeda Galaxy in the Local Group.

The Pegasus Dwarf Spheroidal is a dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Pegasus. The Pegasus Dwarf is a member of the Local Group and a satellite galaxy of the Andromeda Galaxy.

The Phoenix Dwarf is a dwarf galaxy and an irregular galaxy that was discovered in 1976 by Hans-Emil Schuster and Richard Martin West and mistaken for a globular cluster. It is currently 1.44 Mly away from Earth. Its name comes from the fact that it is part of the Phoenix constellation.

The Pinwheel Galaxy is a face-on spiral galaxy distanced 21 million light-years away in the constellation Ursa Major, first discovered by Pierre Méchain on March 27, 1781, and communicated to Charles Messier who verified its position for inclusion in the Messier Catalogue as one of its final entries.
On February 28, 2006, NASA and the ESA released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed from 51 individual exposures, plus some extra ground-based photos.
On August 24, 2011, a Type Ia supernova, SN 2011fe, was discovered in M101.

Pisces Dwarf is an irregular dwarf galaxy that is part of the Local Group. The galaxy is also suspected of being a satellite galaxy of the Triangulum Galaxy. Because it is in the constellation Pisces, the galaxy is called the Pisces Dwarf. It displays a blueshift, as it is approaching the Milky Way at 287 km/s. It may be transition-type galaxy, somewhere between dwarf spheroidal and dwarf irregular. Alternatively, it may be a rare, but statistically acceptable, version of one of the two types.

The Sagittarius Dwarf Irregular Galaxy or SagDIG is a dwarf galaxy in the constellation of Sagittarius. It lies about 3.4 million light-years away. SagDIG should not be confused with the Sagittarius Dwarf Elliptical Galaxy or SagDEG, a satellite galaxy of the Milky Way. It was discovered by Cesarsky et al. on a photographic plate taken for the ESO Atlas on June 13, 1977 using the ESO 1 meter Schmidt telescope.
The SagDIG is the most remote object from the barycenter thought to be a member of the Local Group. It is only slightly outside the zero-velocity surface of the Local Group.
SagDIG is a much more luminous galaxy than Aquarius Dwarf and it has been through a prolonged star formation. This has resulted in it containing a rich intermediate-age population of stars. Twenty-seven candidate carbon stars have been identified inside SagDIG. Analysis shows that the underlying stellar population of SagDIG is metal-poor. Further, the population is young, with the most likely average age between 4 and 8 billion years for the dominant population.

The Sagittarius Dwarf Spheroidal Galaxy, also known as the Sagittarius Dwarf Elliptical Galaxy, is an elliptical loop-shaped satellite galaxy of the Milky Way. It consists of four globular clusters, the main cluster having been discovered in 1994. Sag DEG is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit at a distance of about 50,000 light-years from the core of the Milky Way. In its looping, spiraling path, it has passed through the plane of the Milky Way several times in the past.

The Sculptor Dwarf Galaxy is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the constellation Sculptor. It was discovered in 1937 by Harlow Shapley using the 24-inch Bruce refractor at Boyden Observatory. The galaxy is located about 290,000 light-years away from the Solar System. The Sculptor Dwarf contains only 4 percent of the carbon and other heavy elements in our own galaxy, the Milky Way, making it similar to primitive galaxies seen at the edge of the universe.

The Sculptor Dwarf Irregular Galaxy is an irregular galaxy in the constellation Sculptor. The galaxy was discovered in 1976.

The Sculptor Galaxy, also known as the Silver Coin or Silver Dollar Galaxy, NGC 253, is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.

Sextans A, is a tiny dwarf irregular galaxy. It spans about 5000 light-years across, and is located within the Local Group of galaxies, which includes our Milky Way galaxy. At 4.3 million light-years away from Earth, Sextans A is one of most distant members of the Local Group, and is notable for its peculiar square shape. Massive short-lived stars exploded in supernovae that caused more star formation, triggering yet more supernovae, ultimately resulting in an expanding shell. Young blue stars now highlight areas and shell edges high in current star formation, which from the perspective of observers on Earth appears roughly square.

The Sextans Dwarf Spheroidal is a dwarf spheroidal galaxy that was discovered in 1990 by Mike Irwin, M.T. Bridgeland, P.S. Bunclark and R.G. McMahon as the 8th satellite of the Milky Way, and is named fittingly, as it is located in the constellation of Sextans. It is also an elliptical galaxy, and displays a redshift because it is receding from the Sun at 224 km/s.

The Small Magellanic Cloud is a dwarf galaxy. It is classified as a dwarf irregular galaxy. It has a diameter of about 7,000 light-years and contains several hundred million stars. It has a total mass of approximately 7 billion times the mass of the Sun.
Some speculate that the SMC was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular. It contains a central bar structure.
At a distance of about 200,000 light-years, it is one of the Milky Way's nearest neighbors. It is also one of the most distant objects that can be seen with the naked eye.
With a mean declination of approximately −73 degrees, it can only be viewed from the Southern Hemisphere and the lower latitudes of the Northern Hemisphere. It is located in the constellation of Tucana and appears as a hazy, light patch in the night sky about 3 degrees across. It looks like a detached piece of the Milky Way. Since it has a very low surface brightness, it is best viewed from a dark site away from city lights.
It forms a pair with the Large Magellanic Cloud, which lies a further 20 degrees to the east. The Small Magellanic Cloud is a member of the Local Group.

The Sombrero Galaxy is an unbarred spiral galaxy in the constellation Virgo located 28 million light-years from Earth. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. Astronomers initially thought that the halo was small and light, indicative of a spiral galaxy, but Spitzer found that the halo around the Sombrero Galaxy is larger and more massive than previously thought, indicative of a giant elliptical galaxy. The galaxy has an apparent magnitude of +9.0, making it easily visible with amateur telescopes, and it's considered by some authors to be the brightest galaxy within a radius of 10 megaparsecs of the Milky Way. The large bulge, the central supermassive black hole, and the dust lane all attract the attention of professional astronomers.

A starburst galaxy is a galaxy undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies. In a starburst galaxy, the rate of star formation is so large that the galaxy will consume all of its gas reservoir, from which the stars are forming, on a timescale much shorter than the age of the galaxy. As such, the starburst nature of a galaxy is a phase, and one that typically occupies a brief period of a galaxy's evolution. The majority of starburst galaxies are in the midst of a merger or close encounter with another galaxy. Well-known starburst galaxies include M82, NGC 4038/NGC 4039, and IC 10.

Messier 63 is a spiral galaxy in the constellation Canes Venatici consisting of a central disc surrounded by many short spiral arm segments. M63 is part of the M51 Group, a group of galaxies that also includes M51.

The Tadpole Galaxy is a disrupted barred spiral galaxy located 420 million light-years from Earth toward the northern constellation Draco. Its most dramatic features are a trail of stars about 280,000 light-years long and massive, bright blue star clusters.
It is hypothesized that a more compact intruder galaxy crossed in front of the Tadpole Galaxy—from left to right from the perspective of Earth—and was slung around behind the Tadpole by their mutual gravitational attraction. During this close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust, forming the conspicuous tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.

The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598, and is sometimes informally referred to as the Pinwheel Galaxy, a nickname it shares with Messier 101. The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, which includes the Milky Way, the Andromeda Galaxy and about 44 other smaller galaxies. It is one of the most distant permanent objects that can be viewed with the naked eye.

UDFj-39546284 is the designation given to a stellar structure reported January 27, 2011, as light from the oldest object detected through infrared observation within the Hubble Space Telescope. The object was identified by G. Illingworth, R. Bouwens and the HUDF09 Team during 2009 and 2010 and is in the Fornax constellation. It was initially thought to be at redshift z~10 using Hubble and Spitzer telescope photometric data, including Hubble Extreme Deep Field. Subsequently it was reported to possibly be at a record-breaking redshift z = 11.9 using Hubble and Spitzer telescope data, including Hubble Ultra-Deep Field. Recent analyses have suggested this source is more likely to be a low redshift interloper, with extreme emission lines in its spectrum producing the appearance of a very high redshift source.

UDFy-38135539 is the Hubble Ultra Deep Field identifier for a galaxy which was calculated as of October 2010 to have a light travel time of 13.1 billion years with a present proper distance of around 30 billion light-years.
It was discovered by three teams in September 2009 in sensitive infrared Hubble Space Telescope images and identified by these as source UDF-38135539 source HUDF.YD3 and source 1721, and additionally reported in the Astrophysical Journal, and the Monthly Notices of the Royal Astronomical Society. All teams independently identified the source likely an extremely distant galaxy because there were no measurable light at visible wavelengths. Following the discovery of this candidate distant galaxy, another team targeted this object with ground-based spectroscopy to confirm the distance, reporting a redshift of 8.6. However, attempts to replicate this observation strongly suggest the original claim was in error, meaning that at the present time the galaxy only has a photometric redshift estimate.

Ursa Major I Dwarf is a dwarf spheroidal galaxy orbiting the Milky Way galaxy. The discovery by Beth Willman et al. was announced in 2005.
Being a small dwarf galaxy, it measures only a few thousand light-years in diameter. As of 2006, it is the third least luminous galaxy known, after the Boötes Dwarf and the more recently discovered Ursa Major II Dwarf. The absolute magnitude of the galaxy is estimated to be only −6.75, meaning that it is less luminous than some stars, like Deneb in the Milky Way. It is comparable in luminosity to Rigel. It has been described as similar to the Sextans Dwarf Galaxy. Both galaxies are ancient and metal-deficient.
It estimated to be located at a distance of about 330,000 light-years from the Earth. That is about twice the distance to the Large Magellanic Cloud; the largest and most luminous satellite galaxy of the Milky Way.
There was another object called Ursa Major Dwarf, discovered by Edwin Hubble in 1949. It was designated as Palomar 4. Due to its peculiar look, it was temporarily suspected to be either a dwarf spheroidal or elliptical galaxy. However, it has since been found to be a very distant globular cluster belonging to our galaxy.

The Ursa Minor Dwarf dwarf spheroidal galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. It is part of the Ursa Minor constellation, and a satellite galaxy to the Milky Way. The galaxy consists mainly of older stars and there appears to be little to no ongoing star formation in the Ursa Minor Dwarf galaxy. Its centre is around 225,000 light years distant from Earth.

The Virgo Stellar Stream, also known as Virgo Overdensity, is the proposed name for a stellar stream in the constellation of Virgo which was discovered in 2005. The stream is thought to be the remains of a dwarf spheroidal galaxy that is in the process of merging with the Milky Way. It is the largest galaxy visible from the Earth, in terms of the area of the night sky covered.
The stream was discovered from photometric data from the Sloan Digital Sky Survey, which was used to create a three-dimensional map of the Milky Way, using the colors and brightness of certain characteristic types of stars to estimate their distance. The first suggestion of a new galaxy in Virgo was made in 2001 from data obtained as part of the QUEST survey, which used the 1.0 metre Schmidt telescope at the Llano del Hato National Astronomical Observatory in Venezuela to look for RR Lyrae variable stars. Five were found in a clump with a right ascension near 12.4 hours, and the astronomers speculated that this clump was part of a small galaxy being "cannibalised" by the Milky Way.
The stream covers over 100 square degrees, and possibly as much as 1,000 square degrees.

The Whirlpool Galaxy is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus in the constellation Canes Venatici. Recently it was estimated to be 23 ± 4 million light-years from the Milky Way, but different methods yield distances between 15 and 35 million ly. Messier 51 is one of the best known galaxies in the sky. The galaxy and its companion are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure and galaxy interactions.

The Wolf–Lundmark–Melotte is an irregular galaxy discovered in 1909 by Max Wolf, and is located on the outer edges of the Local Group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.

The Arietids are a strong meteor shower that lasts from May 22 to July 2 each year, and peaks on June 7. The Arietids, along with the Zeta Perseids, are the most intense daylight meteor showers of the year. The source of the shower is unknown, but scientists suspect that they come from the asteroid 1566 Icarus, although the orbit also corresponds similarly to 96P/Machholz.
First discovered at Jodrell Bank Observatory in England during the summer of 1947, the showers are caused when the Earth passes through a dense portion of two interplanetary meteoroid streams, producing an average of 60 shooting stars each hour, that originate in the sky from the constellation Aries and the constellation Perseus. However, because both constellations are so close to the Sun when these showers reach their peak, the showers are difficult to view with the naked eye. Some of the early meteors are visible in the very early hours of the morning, usually an hour before dawn. The meteors strike Earth's atmosphere at speeds around 39 km/s.

The Geminids are a meteor shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid with a "rock comet" orbit. This would make the Geminids, together with the Quadrantids, the only major meteor showers not originating from a comet. The meteors from this shower are slow moving, can be seen in December and usually peak around December 13–14, with the date of highest intensity being the morning of December 14. The shower is thought to be intensifying every year and recent showers have seen 120–160 meteors per hour under optimal conditions, generally around 02:00 to 03:00 local time. Geminids were first observed in 1862, much more recently than other showers such as the Perseids and Leonids.

The Leonids are a prolific meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. Their proper Greek name should be Leontids, but the word was initially constructed as a Greek/Latin hybrid and it has been used since. They peak in the month of November.
Earth moves through the meteoroid stream of particles left from the passages of a comet. The stream comprises solid particles, known as meteoroids, ejected by the comet as its frozen gases evaporate under the heat of the Sun when it is close enough – typically closer than Jupiter's orbit. The Leonids are a fast moving stream which encounter the path of Earth and impact at 72 km/s. Larger Leonids which are about 10 mm across have a mass of half a gram and are known for generating bright meteors. An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet.
The meteoroids left by the comet are organized in trails in orbits similar to though different from that of the comet.

The Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion, but they can be seen over a large area of the sky. Orionids are an annual meteor shower which last approximately one week in late-October. In some years, meteors may occur at rates of 50-70 per hour.

The Perseids are a prolific meteor shower associated with the comet Swift–Tuttle. The Perseids are so called because the point from which they appear to come, called the radiant, lies in the constellation Perseus. The name derives in part from the word Perseides, a term found in Greek mythology referring to the sons of Perseus.
The stream of debris is called the Perseid cloud and stretches along the orbit of the comet Swift–Tuttle. The cloud consists of particles ejected by the comet as it travels on its 133-year orbit. Most of the particles have been part of the cloud for around a thousand years. However, there is also a relatively young filament of dust in the stream that was pulled off the comet in 1865, which can give an early mini-peak the day before the maximum shower.
The earliest information on this meteor shower is found in Chinese annals in A.D. 36. However, credit for recognising the shower's annual appearance is given to Adolphe Quetelet, who reported in 1835 that there was a shower emanating from the constellation Perseus. Some Catholics refer to the Perseids as the "tears of Saint Lawrence", since 10 August is the date of that saint's martyrdom.

The Quadrantids are a January meteor shower. The zenithal hourly rate of this shower can be as high as two other reliably rich meteor showers, the Perseids in August and the Geminids in December. Yet Quadrantid meteors are not seen as often as meteors in these other two showers, because the peak intensity is exceedingly sharp, sometimes lasting only hours.
The meteor rates exceed one-half of their highest value for only about 8 hours. This means that the stream of particles that produces this shower is narrow – and apparently deriving from and within the last 500 years from some orbiting body. The parent body of the Quadrantids was tentatively identified in 2003 by Peter Jenniskens as the minor planet 2003 EH1, which in turn may be related to the comet C/1490 Y1 that was observed by Chinese, Japanese and Korean astronomers some 500 years ago.
The radiant point of this shower is an area inside the constellation Boötes, not far from the Big Dipper. It lies between the end of the handle of the Big Dipper and the quadrilateral of stars marking the head of the constellation Draco.

Amalthea is the third moon of Jupiter in order of distance from the planet. It was discovered on September 9, 1892, by Edward Emerson Barnard and named after Amalthea, a nymph in Greek mythology. It is also known as Jupiter V.
Amalthea is in a close orbit around Jupiter and is within the outer edge of the Amalthea Gossamer Ring, which is formed from dust ejected from its surface. From its surface, Jupiter would be an astonishing sight in its sky, appearing 46.5 degrees in diameter. Amalthea is the largest of the inner satellites of Jupiter. Irregularly shaped and reddish in color, it is thought to consist of porous water ice with unknown amounts of other materials. Its surface features include large craters and ridges.
Amalthea was photographed in 1979 and 1980 by the Voyager 1 and 2 spacecraft, and later, in more detail, by the Galileo orbiter in the 1990s.

Ariel is the fourth-largest of the 27 known moons of Uranus. Ariel orbits and rotates in the equatorial plane of Uranus, which is almost perpendicular to the orbit of Uranus, and so has an extreme seasonal cycle.
It was discovered in October 1851 by William Lassell, and named for a character in two different pieces of literature. As of 2012, much of the detailed knowledge of Ariel derives from a single flyby of Uranus performed by the spacecraft Voyager 2 in 1986, which managed to image around 35% of the moon's surface. There are no active plans at present to return to study the moon in more detail, although various concepts such as Uranus orbiter and probe are proposed from time to time.
After Miranda, Ariel is the second-smallest of Uranus' five major rounded satellites, and the second-closest to its planet. Among the smallest of the Solar System's 19 known spherical moons, it is believed to be composed of roughly equal parts ice and rocky material.

Atlas is an inner satellite of Saturn.
Atlas was discovered by Richard Terrile in 1980 from Voyager photos and was designated S/1980 S 28. In 1983 it was officially named after Atlas of Greek mythology, because it "holds the rings on its shoulders" like the Titan Atlas held the sky up above the Earth. It is also designated Saturn XV.
Atlas is the closest satellite to the sharp outer edge of the A ring, and was long thought to be a shepherd satellite for this ring. However, now it is known that the outer edge of the ring is instead maintained by a 7:6 orbital resonance with the larger but more distant moons Janus and Epimetheus. In 2004 a faint, thin ring, temporarily designated R/2004 S 1, was discovered in the Atlantean orbit.
High-resolution images taken in June 2005 by Cassini revealed Atlas to be have a roughly spherical centre surrounded by a large, smooth equatorial ridge. The most likely explanation for this unusual and prominent structure is that ring material swept up by the moon accumulates on the moon, with a strong preference for the equator due to the ring's thinness. In fact, the size of the equatorial ridge is comparable with the expected Roche lobe of the moon.

Bianca is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on January 23, 1986, and was given the temporary designation S/1986 U 9. It was named after the sister of Katherine in Shakespeare's play The Taming of the Shrew. It is also designated Uranus VIII.
Bianca belongs to Portia Group of satellites, which also includes Cressida, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda and Perdita. These satellites have similar orbits and photometric properties. Other than its orbit, radius of 27 km, and geometric albedo of 0.08 virtually nothing is known about it.
At the Voyager 2 images Bianca appears as an elongated object, the major axis pointing towards Uranus. The ratio of axes of the Bianca's prolate spheroid is 0.7 ± 0.2. Its surface is grey in color.

Callisto is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede, and the largest object in the solar system not to be properly differentiated. At 4821 km in diameter, Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1880000 km. It does not form part of the orbital resonance that affects three inner Galilean satellites—Io, Europa and Ganymede—and thus does not experience appreciable tidal heating. Callisto's rotation is tidally locked to its revolution around Jupiter, so that the same hemisphere always faces inward; Jupiter appears to stand nearly still in Callisto's sky. It is less affected by Jupiter's magnetosphere than the other inner satellites because of its more remote orbit, located just outside the gas giant's main radiation belt.
Callisto is composed of approximately equal amounts of rock and ices, with a mean density of about 1.83 g/cm³, the lowest density and surface gravity of Jupiter's major moons.

Charon is the largest satellite of the dwarf planet Pluto. It was discovered in 1978 at the United States Naval Observatory Flagstaff Station. Following the 2005 discovery of two other natural satellites of Pluto, and two more in 2011 and 2012, Charon may also be referred to as Pluto I.
The New Horizons mission is scheduled to visit Charon and Pluto in July 2015.

Cressida is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 9 January 1986, and was given the temporary designation S/1986 U 3. It was named after Cressida, the Trojan daughter of Calchas, a tragic heroine who appears in William Shakespeare's play Troilus and Cressida. It is also designated Uranus IX.
Cressida belongs to the Portia Group of satellites, which includes Bianca, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda and Perdita. These satellites have similar orbits and photometric properties. Other than its orbit, radius of 41 km and geometric albedo of 0.08 virtually nothing is known about it.
At the Voyager 2 images Cressida appears as an elongated object, the major axis pointing towards Uranus. The ratio of axes of the Cressida's prolate spheroid is 0.8 ± 0.3. Its surface is grey in color.
Cressida may collide with Desdemona within the next 100 million years.

Cupid is an inner satellite of Uranus. It was discovered by Mark R. Showalter and Jack J. Lissauer in 2003 using the Hubble Space Telescope. It was named after a character in William Shakespeare's play Timon of Athens.
It is the smallest of inner Uranian satellites, crudely estimated to be only about 18 km in diameter. This and the dark surface made it too dim to be detected by the Voyager 2 cameras during its Uranus flyby in 1986.
The orbit of Cupid differs only by 863 km from the orbit of the larger moon Belinda. Unlike Mab and Perdita, Uranian satellites also discovered in 2003, it does not seem to be perturbed.
Following its discovery, Cupid was given the temporary designation S/2003 U 2. It is also designated Uranus XXVII.

Deimos is the smaller and outermore of the two natural satellites of the planet Mars with a mean radius of 6.2 km, the other being Phobos. Deimos takes 30.3 hours to orbit Mars. The name "Deimos" is pronounced DY-məs, or sometimes DEE-məs or like the Greek Δείμος. In Greek mythology, Deimos was the twin brother of Phobos and personified Terror.

Desdemona is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 13 January 1986, and was given the temporary designation S/1986 U 6. Desdemona is named after the wife of Othello in William Shakespeare's play Othello. It is also designated Uranus X.
Desdemona belongs to Portia Group of satellites, which also includes Bianca, Cressida, Juliet, Portia, Rosalind, Cupid, Belinda and Perdita. These satellites have similar orbits and photometric properties. Other than its orbit, radius of 32 km and geometric albedo of 0.08 virtually nothing is known about Desdemona.
At the Voyager 2 images Desdemona appears as an elongated object, the major axis pointing towards Uranus. The ratio of axes of Desdemona's prolate spheroid is 0.6 ± 0.3. Its surface is grey in color.
Desdemona may collide with one of its neighboring moons Cressida or Juliet within the next 100 million years.

Dione is a moon of Saturn discovered by Cassini in 1684. It is named after the Titaness Dione of Greek mythology. It is also designated Saturn IV.

Dysnomia, officially Eris I Dysnomia, is the only known moon of the dwarf planet Eris. It was discovered in 2005 by Mike Brown and the laser guide star adaptive optics team at the W. M. Keck Observatory, and carried the provisional designation of S/2005 1 until officially named Dysnomia after the daughter of the Greek goddess Eris.

Elara is a prograde irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at Lick Observatory in 1905. It is the eighth largest moon of Jupiter and is named after Elara, one of Zeus's lovers and the mother of the giant Tityos.
Elara did not receive its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera" between 1955 and 1975. It has a mean radius of just 43 km meaning it is just 2% the size of Europa. However it is half the size of Himalia so it is the second biggest moon in the Himalia group. It might be a captured type C or D asteroid because it reflects very little light.
Elara belongs to the Himalia group, five moons orbiting between 11 and 13 Gm from Jupiter at an inclination of about 27.5°. Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.

Enceladus is the sixth-largest moon of Saturn. It was discovered in 1789 by William Herschel, but little was known about Enceladus until the two Voyager spacecraft passed near it in the early 1980s. The Voyagers showed that the diameter of Enceladus is only 500 kilometers, about a tenth of that of Saturn's largest moon, Titan, and that it reflects almost all the sunlight that strikes it. Enceladus has a wide range of surfaces ranging from old, heavily cratered regions to young, tectonically deformed terrains that formed as recently as 100 million years ago, despite its small size.
In 2005, the Cassini spacecraft started multiple close flybys of Enceladus, revealing its surface and environment in greater detail. In particular, Cassini discovered a water-rich plume venting from Enceladus's south polar region. Cryovolcanoes near the south pole shoot geyser-like jets of water vapor, other volatiles, and solid material including sodium chloride crystals and ice particles into space, totaling approximately 200 kilograms per second. Over 100 geysers have been identified.

Epimetheus is an inner satellite of Saturn. It is also known as Saturn XI. It is named after the mythological Epimetheus, brother of Prometheus.

Europa, is the sixth-closest moon of the planet Jupiter, and the smallest of its four Galilean satellites, but still the sixth-largest moon in the Solar System. Europa was discovered in 1610 by Galileo Galilei Progressively better observations of Europa have occurred over the centuries by Earth-bound telescopes, and by space probe flybys starting in the 1970s.
Slightly smaller than the Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is striated by cracks and streaks, whereas craters are relatively rare. Being composed of frozen water, it gives the moon the smoothest surface of any solid object in the Solar System. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably serve as an abode for extraterrestrial life. This hypothesis proposes that heat from tidal flexing causes the ocean to remain liquid and drives geological activity similar to plate tectonics.

Galatea, also known as Neptune VI, is the fourth closest inner satellite of Neptune. It is named after Galatea, one of the Nereids of Greek legend.
Galatea was discovered in late July 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 4 The discovery was announced on August 2, 1989, but the text only talks of "10 frames taken over 5 days", giving a discovery date of sometime before July 28. The name was given on 16 September 1991.
It is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.
Galatea's orbit lies below Neptune's synchronous orbit radius, so it is slowly spiralling inward due to tidal deceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching.
Galatea appears to be a shepherd moon for the Adams ring that is 1000 km outside its orbit.

Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively. It has a diameter of 5,268 km, 8% larger than that of the planet Mercury, but has only 45% of the latter's mass. Its diameter is 2% larger than that of Saturn's Titan, the second largest moon. It also has the highest mass of all planetary satellites, with 2.02 times the mass of the Earth's moon.
Ganymede is composed of approximately equal amounts of silicate rock and water ice. It is a fully differentiated body with an iron-rich, liquid core, and it might have ice and oceans stacked up in several layers. Its surface is composed of two main types of terrain. Dark regions, saturated with impact craters and dated to four billion years ago, cover about a third of the satellite. Lighter regions, crosscut by extensive grooves and ridges and only slightly less ancient, cover the remainder.

Hydra is the outermost known natural satellite of Pluto. It was discovered along with Nix in June 2005, and is to be visited along with Pluto by the New Horizons mission in July 2015.

Hyperion, also known as Saturn VII, is a moon of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. It is distinguished by its irregular shape, its chaotic rotation, and its unexplained sponge-like appearance. It was the first non-round moon to be discovered.

Iapetus, or occasionally Japetus, is the third-largest natural satellite of Saturn, eleventh-largest in the Solar System, and the largest body in the Solar System known not to be in hydrostatic equilibrium. Iapetus is best known for its dramatic 'two-tone' coloration, but discoveries by the Cassini mission in 2007 have revealed several other unusual features, such as a massive equatorial ridge that runs three quarters of the way around Iapetus.

Io is the innermost of the four Galilean moons of the planet Jupiter. It is the fourth-largest moon, has the highest density of all the moons, and is the driest known object in the Solar System. It was named after the mythological character Io, a priestess of Hera who became one of Zeus's lovers.
With over 400 active volcanoes, Io is the most geologically active object in the Solar System. This extreme geologic activity is the result of tidal heating from friction generated within Io's interior as it is pulled between Jupiter and the other Galilean satellites—Europa, Ganymede and Callisto. Several volcanoes produce plumes of sulfur and sulfur dioxide that climb as high as 500 km above the surface. Io's surface is also dotted with more than 100 mountains that have been uplifted by extensive compression at the base of Io's silicate crust. Some of these peaks are taller than Mount Everest. Unlike most satellites in the outer Solar System, which are mostly composed of water ice, Io is primarily composed of silicate rock surrounding a molten iron or iron sulfide core. Most of Io's surface is composed of extensive plains coated with sulfur and sulfur dioxide frost.

Janus is an inner satellite of Saturn. It is also known as Saturn X. It is named after the mythological Janus.

Mab, or Uranus XXVI, is an inner satellite of Uranus. It was discovered by Mark R. Showalter and Jack J. Lissauer in 2003 using the Hubble Space Telescope. It was named after Queen Mab, a fairy queen from English folklore who is mentioned in William Shakespeare's play Romeo and Juliet.
Because the moon is small and dark, it was not seen in the heavily scrutinized images taken by Voyager 2 during its Uranus flyby in 1986. However, it is brighter than another moon, Perdita, which was discovered from Voyager's photos in 1997. This led scientists to re-examine the old photos again, and the satellite was finally found in the images.
The size of Mab is not known exactly. If it is as dark as Puck, it is about 24 km in diameter. On the other hand, if it is brightly coloured like the neighbouring moon Miranda, it would be even smaller than Cupid and comparable to the smallest outer satellites.
Mab is heavily perturbed. The actual source for perturbation is still unclear, but is presumed to be one or more of the nearby orbiting moons.
Mab orbits at the same distance from Uranus as the μ ring, a recently discovered dusty ring.

Metis, also known as Jupiter XVI, is the innermost moon of Jupiter. It was discovered in 1979 in images taken by Voyager 1, and was named in 1983 after the first wife of Zeus, Metis. Additional observations made between early 1996 and September 2003 by the Galileo spacecraft allowed the surface of the moon to be imaged.
Metis is tidally locked to Jupiter, and its shape is strongly asymmetrical, with one of the diameters being almost twice as large as the smallest one. It is also one of the two moons known to orbit Jupiter in less than the length of Jupiter's day, the other being Adrastea. It orbits within the main ring of Jupiter, and is thought to be a major contributor of material to the rings.

Mimas is a moon of Saturn which was discovered in 1789 by William Herschel. It is named after Mimas, a son of Gaia in Greek mythology, and is also designated Saturn I.
With a diameter of 396 kilometres it is the twenty-first-largest moon in the Solar System and is the smallest astronomical body that is known to be rounded in shape because of self-gravitation.

Miranda or Uranus V is the smallest and innermost of Uranus's five round satellites. Like the 27 other moons of Uranus, Miranda orbits in its planet's equatorial plane. Because Uranus orbits the Sun on its side, Miranda's orbit is perpendicular to the ecliptic and shares Uranus's extreme seasonal cycle. At just 470 km in diameter, Miranda is one of the smallest objects in the Solar System known to be spherical under its own gravity. Of the bodies that are known to be in hydrostatic equilibrium, only Saturn's moon Mimas is smaller.
Miranda has one of the most extreme and varied topographies of any object in the Solar System, including Verona Rupes, a 20-kilometer-high scarp that is the tallest cliff in the Solar System, and chevron-shaped tectonic features called coronae. The origin and evolution of this varied geology, the most of any Uranian satellite, is still not fully understood, and multiple hypotheses exist regarding Miranda's formation.
Miranda was discovered by Gerard Kuiper on 16 February 1948 at McDonald Observatory, and named after Miranda from William Shakespeare's play The Tempest.

Nereid is the third-largest moon of Neptune. It has a highly eccentric orbit. It was the second moon of Neptune to be discovered, by Gerard Kuiper in 1949.

Nix is a natural satellite of Pluto. It was discovered along with Hydra in June 2005, and is to be visited along with Pluto by the New Horizons mission in July 2015.

Oberon, also designated Uranus IV, is the outermost major moon of the planet Uranus. It is the second-largest and second most massive of the Uranian moons, and the ninth most massive moon in the Solar System. Discovered by William Herschel in 1787, Oberon is named after the mythical king of the fairies who appears as a character in Shakespeare's A Midsummer Night's Dream. Its orbit lies partially outside Uranus's magnetosphere.
It is likely that Oberon formed from the accretion disk that surrounded Uranus just after the planet's formation. The moon consists of approximately equal amounts of ice and rock, and is probably differentiated into a rocky core and an icy mantle. A layer of liquid water may be present at the boundary between the mantle and the core. The surface of Oberon, which is dark and slightly red in color, appears to have been primarily shaped by asteroid and comet impacts. It is covered by numerous impact craters reaching 210 km in diameter. Oberon possesses a system of chasmata formed during crustal extension as a result of the expansion of its interior during its early evolution.

Ophelia is a moon of Uranus. It was discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 8. It was not seen until the Hubble Space Telescope recovered it in 2003. Ophelia was named after the daughter of Polonius, Ophelia, in William Shakespeare's play Hamlet. It is also designated Uranus VII.
Other than its orbit, radius of 21 km and geometric albedo of 0.08 virtually nothing is known about it. At the Voyager 2 images Ophelia appears as an elongated object, the major axis pointing towards Uranus. The ratio of axes of the Ophelia's prolate spheroid is 0.7 ± 0.3.
Ophelia acts as the outer shepherd satellite for Uranus' Epsilon ring. The orbit of Ophelia is within the synchronous orbit radius of Uranus, and therefore the moon is slowly decaying due to tidal forces.

Pandora is an inner satellite of Saturn. It was discovered in 1980 from photos taken by the Voyager 1 probe, and was provisionally designated S/1980 S 26. In late 1985 it was officially named after Pandora from Greek mythology. It is also designated as Saturn XVII.
Pandora was thought to be an outer shepherd satellite of the F Ring. Recent observations have disproved this. It is more heavily cratered than nearby Prometheus, and has at least two large craters 30 kilometres in diameter. The majority of craters on Pandora are shallow as a result of being filled with debris. Ridges and grooves are also present on moon's surface.
The orbit of Pandora appears to be chaotic, as a consequence of a series of four 118:121 mean motion resonances with Prometheus. The most appreciable changes in their orbits occur approximately every 6.2 years, when the periapsis of Pandora lines up with the apoapsis of Prometheus and the moons approach to within about 1,400 kilometres. Pandora also has a 3:2 mean-motion resonance with Mimas.
From its very low density and relatively high albedo, it seems likely that Pandora is a very porous icy body.

Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877.
A small, irregularly shaped object with a mean radius of 11 km, Phobos is seven times more massive than Mars's outer moon, Deimos. Phobos is named after the Greek god Phobos, a son of Ares and Aphrodite which was the personification of Horror. The name "Phobos" is pronounced FOH-bəs, or like the Greek Φόβος.
Phobos orbits 6,000 km from the Martian surface, closer to its primary than any other known planetary moon. It is so close that it orbits Mars faster than Mars rotates, and completes an orbit in just 7 hours and 39 minutes. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 hours 15 min or less, and set in the east, twice each Martian day. Due to tidal interactions, Phobos is drawing closer to Mars by one meter every century, and it is predicted that in 50 million years it will collide with the planet or break up into a planetary ring.
Phobos is one of the least reflective bodies in the Solar System, and features a large impact crater, Stickney.

Phoebe is an irregular satellite of Saturn a little over 200 km in diameter. It is thought to be a captured planetesimal from the Kuiper belt. It was discovered by William Henry Pickering on 17 March 1899 from photographic plates that had been taken starting on 16 August 1898 at the Boyden Observatory near Arequipa, Peru, by DeLisle Stewart. It was the first satellite to be discovered photographically.
Phoebe was the first target encountered upon the arrival of the Cassini spacecraft to the Saturn system in 2004, and is thus unusually well-studied for a natural satellite of its size. Cassini's trajectory to Saturn and time of arrival were specifically chosen to permit this flyby. After the encounter and its insertion into orbit, Cassini would not go much beyond the orbit of Iapetus.

Prometheus is an inner satellite of Saturn. It was discovered in 1980 from photos taken by the Voyager 1 probe, and was provisionally designated S/1980 S 27.
In late 1985 it was officially named after Prometheus, a Titan in Greek mythology. It is also designated Saturn XVI. Pronunciation for Prometheus is, US dict: prō·mē′·thē·əs; Greek: Προμηθεύς.
This small moon is extremely elongated, measuring about 136 by 79 by 59 km. It has several ridges and valleys and a number of impact craters of about 20 km diameter are visible, but it is less cratered than nearby Pandora, Epimetheus and Janus. From its very low density and relatively high albedo, it seems likely that Prometheus is a very porous icy body. There is a lot of uncertainty in these values, however, and so this remains to be confirmed.

Proteus, also known as Neptune VIII, is the second largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 spacecraft in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology. Proteus circles Neptune in a nearly equatorial orbit at the distance of about 4.75 equatorial radii of the planet.
Despite being more than 400 km in diameter Proteus has a somewhat irregular shape with several slightly concave facets and relief as high as 20 km. Its surface is dark, neutral in color and heavily cratered. The largest crater is more than 200 km in diameter. There are also a number of scarps, grooves and valleys related to large craters.
Proteus is probably not an original body that formed with Neptune; it may have accreted later from the debris created when the largest Neptunian satellite Triton was captured.

Rhea is the second-largest moon of Saturn and the ninth-largest moon in the Solar System. It is the smallest body in the Solar System confirmed to be in hydrostatic equilibrium. It was discovered in 1672 by Giovanni Domenico Cassini.

Tethys or Saturn III is a mid-sized moon of Saturn about 1,060 km across. It was discovered by G. D. Cassini in 1684 and is named after the titan Tethys of Greek mythology.
Tethys has a low density of 0.98 g/cm³, the lowest of all the major moons in the Solar System, indicating that it is made of water ice with just a small fraction of rock. This is confirmed by the spectroscopy of its surface, which identified water ice as the dominant surface material. A small amount of an unidentified dark material is present as well. The surface of Tethys is very bright, being the second-brightest of the moons of Saturn after Enceladus, and neutral in color.
Tethys is heavily cratered and cut by a number of large faults/graben. The largest impact crater, Odysseus, is about 400 km in diameter, while the largest graben, Ithaca Chasma, is about 100 km wide and more than 2000 km long. These two largest surface features may be related. A small part of the surface is covered by smooth plains that may be cryovolcanic in origin. Like all other regular moons of Saturn, Tethys formed from the Saturnian sub-nebula—a disk of gas and dust that surrounded Saturn soon after its formation.

Thalassa, also known as Neptune IV, is the second innermost satellite of Neptune. Thalassa was named after sea goddess Thalassa, a daughter of Aether and Hemera from Greek mythology. "Thalassa" is also the Greek word for "sea".
Thalassa was discovered sometime before mid-September 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 5. The discovery was announced on September 29, 1989, but the text only talks of "25 frames taken over 11 days", giving a discovery date of sometime before September 18. The name was given on 16 September 1991.
Thalassa is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit. Unusually for irregular bodies, it appears to be roughly disk-shaped.

Titan is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.
Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter 50% larger than Earth's natural satellite, the Moon, and is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter's moon Ganymede, and is larger by volume than the smallest planet, Mercury, although only 40% as massive. Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the fifth known satellite of another planet.
Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan's surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan's polar regions.

Titania is the largest of the moons of Uranus and the eighth largest moon in the Solar System at a diameter of 1,578 kilometres. Discovered by William Herschel in 1787, Titania is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream. Its orbit lies inside Uranus's magnetosphere.
Titania consists of approximately equal amounts of ice and rock, and is probably differentiated into a rocky core and an icy mantle. A layer of liquid water may be present at the core–mantle boundary. The surface of Titania, which is relatively dark and slightly red in color, appears to have been shaped by both impacts and endogenic processes. It is covered with numerous impact craters reaching up to 326 kilometres in diameter, but is less heavily cratered than the surface of Uranus's outermost moon, Oberon. Titania probably underwent an early endogenic resurfacing event which obliterated its older, heavily cratered surface. Titania's surface is cut by a system of enormous canyons and scarps, the result of the expansion of its interior during the later stages of its evolution.

Triton is the largest moon of the planet Neptune, discovered on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, which is an orbit in the opposite direction to its planet's rotation. At 2,700 kilometres in diameter, it is the seventh-largest moon in the Solar System. Because of its retrograde orbit and composition similar to Pluto's, Triton is thought to have been captured from the Kuiper belt. Triton has a surface of mostly frozen nitrogen, a mostly water ice crust, an icy mantle and a substantial core of rock and metal. The core makes up two-thirds of its total mass. Triton has a mean density of 2.061 grams per cubic centimetre and is composed of approximately 15–35% water ice.
Triton is one of the few moons in the Solar System known to be geologically active. As a consequence, its surface is relatively young, with a complex geological history revealed in intricate and mysterious cryovolcanic and tectonic terrains. Part of its crust is dotted with geysers thought to erupt nitrogen. Triton has a tenuous nitrogen atmosphere less than 1/70,000 the pressure of Earth's atmosphere at sea level.

Umbriel is a moon of Uranus discovered on October 24, 1851, by William Lassell. It was discovered at the same time as Ariel and named after a character in Alexander Pope's poem The Rape of the Lock. Umbriel consists mainly of ice with a substantial fraction of rock, and may be differentiated into a rocky core and an icy mantle. The surface is the darkest among Uranian moons, and appears to have been shaped primarily by impacts. However, the presence of canyons suggests early endogenic processes, and the moon may have undergone an early endogenically driven resurfacing event that obliterated its older surface.
Covered by numerous impact craters reaching 210 km in diameter, Umbriel is the second most heavily cratered satellite of Uranus after Oberon. The most prominent surface feature is a ring of bright material on the floor of Wunda crater. This moon, like all moons of Uranus, probably formed from an accretion disk that surrounded the planet just after its formation. The Uranian system has been studied up close only once, by the spacecraft Voyager 2 in January 1986. It took several images of Umbriel, which allowed mapping of about 40% of the moon’s surface.

Ymir, or Saturn XIX, is a retrograde irregular moon of Saturn. It was discovered by Brett J. Gladman, et al. in 2000, and given the temporary designation S/2000 S 1. It was named in August 2003, from Norse mythology, where Ymir is the ancestor of all the Jotuns or frost giants.
Of the moons that take more than 3 Earth years to orbit Saturn, Ymir is the largest, at about 18 kilometres in diameter. It takes 3.6 Earth years to complete an orbit around Saturn. During this time, hypothetical Ymir visitors would experience ~2650 sunsets.

The Carina Nebula is a large bright nebula that has within its boundaries several related open clusters of stars. Some papers generally refer to this as the Carina Nebula, mostly because of differentiating the many papers published on this object, but the historical precedence as determined by southern observers like James Dunlop and John Herschel, who have both termed it the Eta Argus Nebula or Eta Carinae Nebula. John Herschel also describes "The star η Argus, with the Great nebula about it." with many of his subsequent published papers supporting this.
It contains the two large OB associations Carina OB1 and Carina OB2. Carina OB1 contains the two star clusters Trumpler 14 and Trumpler 16. Trumpler 14 is one of the youngest known star clusters, at half a million years old. Trumpler 16 is the home of WR 25, currently the most luminous star known in our Milky Way galaxy, together with the less luminous but more massive and famous Eta Carinae star system, and HD 93129A. The nebula lies at an estimated distance between 6,500 and 10,000 light years from Earth. It appears in the constellation of Carina, and is located in the Carina–Sagittarius Arm.

The Cat's Eye Nebula or NGC 6543, is a planetary nebula in the constellation of Draco. Structurally, it is one of the most complex nebulae known, with high-resolution Hubble Space Telescope observations revealing remarkable structures such as knots, jets, bubbles and sinewy arc-like features. In the center of the Cat's Eye there is a bright and hot star illuminating the surrounding nebula.
Discovered by William Herschel on February 15, 1786, it was the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins in 1864. The results of the latter investigation demonstrated for the first time that planetary nebulae consist of hot gases, but not stars. The nebula has been observed across the full electromagnetic spectrum, from far-infrared to X-rays.
Modern studies reveal several mysteries. The intricacy of the structure may be caused in part by material ejected from a binary central star, but as yet, there is no direct evidence that the central star has a companion. Also, measurements of chemical abundances reveal a large discrepancy between measurements done by two different methods, the cause of which is uncertain.

The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus. Corresponding to a bright supernova recorded by Chinese astronomers in 1054, the nebula was observed later by English astronomer John Bevis in 1731. At an apparent magnitude of 8.4, comparable to that of the largest moon of Saturn, it is not visible to the naked eye but can be made out using binoculars under favourable conditions.
At X-ray and gamma ray energies above 30 keV, the Crab is generally the strongest persistent source in the sky, with measured flux extending to above 10 TeV. Located at a distance of about 6,500 light-years from Earth, the nebula has a diameter of 11 light years and expands at a rate of about 1,500 kilometers per second. It is part of the Perseus Arm of the Milky Way galaxy.
At the center of the nebula lies the Crab Pulsar, a neutron star 28–30 km across with a spin rate of 30.2 times per second, which emits pulses of radiation from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion.

The Dumbbell Nebula is a planetary nebula in the constellation Vulpecula, at a distance of about 1,360 light years.
This object was the first planetary nebula to be discovered; by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and its diameter of about 8 arcminutes, it is easily visible in binoculars, and a popular observing target in amateur telescopes.
M27 in Vulpecula constellation.
Image from the Spitzer Space Telescope.
Image from a ground-based telescope at Westview Observatory in Cridersville, OH

The Eagle Nebula is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745-46. Its name derives from its shape that is thought to resemble an eagle. It contains several active star-forming gas and dust regions, including the famous "Pillars of Creation", photographed by the Hubble Space Telescope.

The Helix Nebula, also known as The Helix, NGC 7293, is a large planetary nebula located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, this object is one of the closest to the Earth of all the bright planetary nebulae. The estimated distance is about 215 parsecs or 700 light-years. It is similar in appearance to the Cat's Eye Nebula and the Ring Nebula, whose size, age, and physical characteristics are similar to the Dumbbell Nebula, varying only in its relative proximity and the appearance from the equatorial viewing angle. The Helix Nebula has sometimes been referred to as the "Eye of God" in pop culture, as well as the "Eye of Sauron".

The Horsehead Nebula is a dark nebula in the constellation Orion. The nebula is located just to the south of the star Alnitak, which is farthest east on Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. The nebula was first recorded in 1888 by Scottish astronomer Williamina Fleming on photographic plate B2312 taken at the Harvard College Observatory. The Horsehead Nebula is approximately 1500 light years from Earth. It is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gases, which bears some resemblance to a horse's head when viewed from Earth.
The dark cloud of dust and gas is a region in the Orion Molecular Cloud Complex where star formation is taking place. This stellar nursery, as it is known, can contain over 100 known organic and inorganic gases as well as dust consisting of large and complex organic molecules.
The red or pinkish glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. Magnetic fields channel the gases leaving the nebula into streams, shown as streaks in the background glow.

The Lagoon Nebula is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as a H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. A fragile star cluster appears superimposed on it.

The Omega Nebula, also known as the Swan Nebula, Checkmark Nebula, Lobster Nebula, and the Horseshoe Nebula is an H II region in the constellation Sagittarius. It was discovered by Philippe Loys de Chéseaux in 1745. Charles Messier catalogued it in 1764. It is located in the rich starfields of the Sagittarius area of the Milky Way.

The Orion Nebula is a diffuse nebula situated in the Milky Way south of Orion's Belt in the constellation of Orion. It is one of the brightest nebulae, and is visible to the naked eye in the night sky. M42 is located at a distance of 1,344 ± 20 light years and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light years across. It has a mass of about 2000 times the mass of the Sun. Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.
The Orion Nebula is one of the most scrutinized and photographed objects in the night sky, and is among the most intensely studied celestial features. The nebula has revealed much about the process of how stars and planetary systems are formed from collapsing clouds of gas and dust. Astronomers have directly observed protoplanetary disks, brown dwarfs, intense and turbulent motions of the gas, and the photo-ionizing effects of massive nearby stars in the nebula.

The Ring Nebula is a planetary nebula in the northern constellation of Lyra. Such objects are formed when a shell of ionized gas is expelled into the surrounding interstellar medium by a red giant star, which was passing through the last stage in its evolution before becoming a white dwarf.

The Tarantula Nebula is an H II region in the Large Magellanic Cloud. It was originally thought to be a star, but in 1751 Nicolas Louis de Lacaille recognized its nebular nature.
The Tarantula Nebula has an apparent magnitude of 8. Considering its distance of about 49 kpc, this is an extremely luminous non-stellar object. Its luminosity is so great that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast shadows. In fact, it is the most active starburst region known in the Local Group of galaxies. It is also one of the largest such region in the Local Group with an estimated diameter of 200 pc. The nebula resides on the leading edge of the LMC, where ram pressure stripping, and the compression of the interstellar medium likely resulting from this, is at a maximum. At its core lies the compact star cluster R136 that produces most of the energy that makes the nebula visible. The estimated mass of the cluster is 450,000 solar masses, suggesting it will likely become a globular cluster in the future.
In addition to R136, the Tarantula Nebula also contains an older star cluster – catalogued as Hodge 301 – with an age of 20–25 million years.

The Trifid Nebula is an H II region located in Sagittarius. It was discovered by Charles Messier on June 5, 1764. Its name means 'divided into three lobes'. The object is an unusual combination of an open cluster of stars; an emission nebula, a reflection nebula and a dark nebula. Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.

Earth, also known as the World, Terra, or Gaia, is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only celestial body known to accommodate life. The Earth's biodiversity has evolved over hundreds of million years, expanding continually except when punctuated by mass extinctions. It is home to over eight million species. There are over 7.2 billion humans who depend upon its biosphere and minerals. The Earth's human population is divided among about two hundred independent states that interact through diplomacy, conflict, travel, trade, and media.
According to evidence from sources such as radiometric dating, the Earth was formed around four and a half billion years ago. Within its first billion years, life appeared in its oceans and began to affect its atmosphere and surface, promoting the proliferation of aerobic as well as anaerobic organisms and causing the formation of the atmosphere's ozone layer. This layer and the geomagnetic field block the most life-threatening parts of the Sun's radiation, so life was able to flourish on land as well as in water.

Eris is the most massive known dwarf planet in the Solar System and the ninth most massive body known to directly orbit the Sun. It is estimated to be 2,326 ± 12 kilometres in diameter, and 27% more massive than Pluto, or about 0.27% of the Earth's mass.
Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its identity was verified later that year. It is a trans-Neptunian object and a member of a high-eccentricity population known as the scattered disc. It has one known moon, Dysnomia. As of 2014, its distance from the Sun is 96.4 astronomical units, roughly three times that of Pluto. With the exception of some comets, Eris and Dysnomia are currently the most distant known natural objects in the Solar System.
Because Eris appeared to be larger than Pluto, its discoverers and NASA initially described it as the Solar System's tenth planet. This, along with the prospect of other similarly sized objects being discovered in the future, motivated the International Astronomical Union to define the term planet for the first time.

Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with mass one-thousandth of that of the Sun but is two and a half times the mass of all the other planets in the Solar System combined. Jupiter is a gas giant, along with Saturn. Uranus and Neptune are ice giants. Together, these four planets are sometimes referred to as the Jovian, giant, or outer planets. The planet was known by astronomers of ancient times. The Romans named the planet after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus.
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, although helium only comprises about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other gas giants, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid.

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often described as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the second highest known mountain within the Solar System, and of Valles Marineris, one of the largest canyons. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan.
Until the first successful Mars flyby in 1965 by Mariner 4, many speculated about the presence of liquid water on the planet's surface.

Mercury is the smallest and closest to the Sun of the eight planets in the Solar System, with an orbital period of about 88 Earth days. Seen from Earth, it appears to move around its orbit in about 116 days, which is much faster than any other planet. It has no known natural satellites. The planet is named after the Roman deity Mercury, the messenger to the gods.
Because it has almost no atmosphere to retain heat, Mercury's surface experiences the greatest temperature variation of all the planets, ranging from 100 K at night to 700 K during the day at some equatorial regions. The poles are constantly below 180 K. Mercury's axis has the smallest tilt of any of the Solar System's planets, but it has the largest orbital eccentricity. As such it does not experience seasons in the same way as most other planets such as Earth. At aphelion, Mercury is about 1.5 times as far from the Sun as it is at perihelion. Mercury's surface is heavily cratered and similar in appearance to the Moon, indicating that it has been geologically inactive for billions of years.
Mercury is gravitationally locked and rotates in a way that is unique in the Solar System.

Neptune is the eighth and farthest planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Among the gaseous planets in the Solar System, Neptune is the most dense. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth but not as dense. Neptune orbits the Sun at an average distance of 30.1 astronomical units. Named after the Roman god of the sea, its astronomical symbol is ♆, a stylised version of the god Neptune's trident.
Neptune was the first planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier, and its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 13 moons were located telescopically until the 20th century.

Pluto is the largest object in the Kuiper belt; the tenth-most-massive known body directly orbiting the Sun; and the second-most-massive known dwarf planet, after Eris. Like other Kuiper belt objects, Pluto is primarily made of rock and ice, and relatively small, about 1/6 the mass of the Moon and 1/3 its volume. It has an eccentric and highly inclined orbit that takes it from 30 to 49 AU from the Sun. Hence Pluto periodically comes closer to the Sun than Neptune, but an orbital resonance with Neptune prevents the bodies from colliding. In 2014 it was 32.6 AU from the Sun.
Discovered in 1930, Pluto was originally classified as the ninth planet from the Sun. Its status as a major planet fell into question following further study of it and the outer Solar System over the next 75 years. Starting in 1977 with the discovery of the minor planet Chiron, numerous icy objects similar to Pluto with eccentric orbits were found. The most notable of these is the scattered disc object Eris, discovered in 2005, which is 27% more massive than Pluto.

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god of agriculture, its astronomical symbol represents the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth. Although only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive.
Saturn's interior is probably composed of a core of iron, nickel and rock, surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer. The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is weaker than Earth's magnetic field but has a magnetic moment 580 times that of the Earth due to Saturn's larger body radius. Saturn's magnetic field strength is around one-twentieth the strength of Jupiter's. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear.

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both are of different chemical composition to the larger gas giants Jupiter and Saturn. Thus, astronomers sometimes place them in a separate category called "ice giants". Uranus's atmosphere, although similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, contains more "ices", such as water, ammonia, and methane, along with traces of other hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K, and has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane the uppermost layer of clouds. In contrast, the interior of Uranus is mainly composed of ices and rock.
It is the only planet whose name is derived from a figure from Greek mythology rather than Roman mythology like the other planets, from the Latinized version of the Greek god of the sky, Ouranos. Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons.

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has no natural satellite. It is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°.
Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, gravity, and bulk composition. However, it has also been shown to be radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of 735 K, Venus is by far the hottest planet in the Solar System. It has no carbon cycle to lock carbon back into rocks and surface features, nor does it seem to have any organic life to absorb carbon in biomass.

44 Boötis or i Boötis is a triple star system in the constellation Boötes. It is approximately 41.6 light years from Earth.
The primary component, 44 Boötis A, is a yellow-white G-type main sequence dwarf with a mean apparent magnitude of +4.83. The companion component, 44 Boötis B, is a W Ursae Majoris variable spectroscopic binary. The brightness of the binary varies from magnitude +5.8 to +6.40 with a period of 6.43 hours. The components of the eclipsing binary are separated by 0.008 Astronomical Units, roughly 3 times the distance of the Moon from Earth.
The 44 Boötis system is 42 light-years from Earth.

51 Andromedae is a 4th magnitude star, the 5th brighest in the constellation Andromeda. It does not have a Bayer designation. It is occasionally called by the proper name Nembus in Bayer's Uranometria and Bode's star atlas Uranographia.
Ptolemy included this star in Andromeda in the Almagest, but it was moved into Perseus by Johann Bayer, who designated it Upsilon Persei. Flamsteed moved it back, and the International Astronomical Union made Flamsteed's 51 Andromedae its official designation in 1930.
In Chinese, 天大將軍, meaning Heaven's Great General, refers to an asterism consisting of 51 Andromedae, γ Andromedae, φ Persei, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, β Trianguli, γ Trianguli and δ Trianguli. Consequently, 51 Andromedae itself is known as 天大將軍三
51 Andromedae is an orange K-type giant with an apparent magnitude of +3.59. It is approximately 177 light years from the Earth.

51 Pegasi is a Sun-like star located 50.9 light-years from Earth in the constellation Pegasus. It was the first extrasolar Sun-like star found to have a planet orbiting it.

61 Virginis is a G-type main sequence star slightly less massive than the Sun, located about 27.9 light-years away in the constellation of Virgo. The composition of this star is nearly identical to the Sun.
61 Virginis is the first well-established main-sequence star very similar to the Sun with a potential Super-Earth, though COROT-7 is arguably the first.

Achernar, sometimes spelled Achenar, is the brightest star in the constellation Eridanus and the tenth-brightest star in the night sky. Of the ten apparent brightest stars in the nighttime sky, Achernar is the hottest and bluest in color, being of spectral type B. Lying at the southern tip of Eridanus, the star has an unusually rapid rotational velocity, causing it to become oblate in shape. Achernar is actually a binary star system, with the second star known as Achernar B. The second star is smaller and orbits Achernar A at a distance of roughly 12 astronomical units. Achernar B is of spectral type A.

Albireo is the fifth brightest star in the constellation Cygnus. Although it has the Bayer designation beta, it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni. Albireo appears to the naked eye to be a single star of magnitude 3 but through a telescope, even low magnification views resolve it into a double star. The brighter yellow star makes a striking colour contrast with its fainter blue companion star.

Aldebaran is an orange giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky. The name Aldebaran is Arabic and translates literally as "the follower", presumably because this bright star appears to follow the Pleiades, or "Seven Sisters" star cluster in the night sky.
In 1997 a substellar companion was reported but subsequent observations have not confirmed this claim.

Alnilam is a large blue supergiant star in the constellation of Orion. It has a Bayer designation of Epsilon Orionis. Its Flamsteed designation is 46 Orionis.
It is the 30th brightest star in the sky and is a blue-white supergiant. Together with Mintaka and Alnitak, the three stars make up the belt of Orion, known by many names across many ancient cultures. Alnilam is the middle star.
Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is also one of the 57 stars used in celestial navigation. It is at its highest point in the sky around midnight on December 15.
Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium. Within the next million years, this star may turn into a red supergiant and explode as a supernova. It is surrounded by a molecular cloud, NGC 1990, which it brightens to make a reflection nebula. Its stellar winds may reach up to 2000 km/s, causing it to lose mass about 20 million times more rapidly than the Sun.

Alnitak is a triple star some 736 light years distant in the constellation Orion. It is part of Orion's Belt along with Alnilam and Mintaka, and has a Bayer designation of Zeta Orionis and a Flamsteed designation of 50 Orionis.
The primary star is a hot blue supergiant with an absolute magnitude of -5.25, and is the brightest class O star in the night sky with a visual magnitude of +2.04. It has two bluish 4th magnitude companions, producing a combined magnitude for the trio of +1.72. The stars are members of the Orion OB1 association and the Collinder 70 association.

Alpha Andromedae, which has the traditional names Alpheratz and Sirrah, is the brightest star in the constellation of Andromeda. Located immediately northeast of the constellation of Pegasus, it is the northeastern star of the Great Square of Pegasus. Ptolemy considered Alpha Andromedae to be shared by Pegasus, and Bayer assigned it a designation in both constellations: Alpha Andromedae and Delta Pegasi. When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use.
It is located 97 light-years from Earth. Although it appears to the naked eye as a single star, with overall apparent visual magnitude +2.06, it is actually a binary system composed of two stars in close orbit. The chemical composition of the brighter of the two stars is unusual as it is a mercury-manganese star whose atmosphere contains abnormally high levels of mercury, manganese, and other elements, including gallium and xenon. It is the brightest mercury-manganese star known.

Alpha Aquarii is a single star in the Aquarius. It has the traditional name Sadalmelik, which is derived from Arabic for "Luck of the king". The apparent visual magnitude of 2.94 makes this the second-brightest star in Aquarius. Based upon parallax measurements made during the Hipparcos mission, this star is located at a distance of roughly 520 light-years from Earth.
With an age of 53 million years, this star has evolved into a supergiant with a stellar classification of G2 Ib. It has 6.5 as much mass as the Sun and has expanded to around 77 times the Sun's radius. It is radiating 3,000 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 5,210 K. At this heat, the star glows with the yellow hue of a G-type star. Examination of this star with the Chandra X-ray Observatory shows it to be significantly X-ray deficient compared to G-type main sequence stars. This deficit is a common feature of early G-type giant stars.
Sadalmelik has a visual companion, designated CCDM J22058-0019B, with an apparent visual magnitude of approximately 12.2. It is at an angular separation of 110.4 arcseconds from Sadalmelik along a position angle of 40°.

Alpha Arietis is the Bayer designation for the brightest star in the northern zodiacal constellation of Aries. It has the traditional name Hamal, which comes from the Arabic phrase for "head of the ram", and the Flamsteed designation of 13 Arietis. With an apparent visual magnitude of 2.0, it is among the brightest stars in the night sky. Based upon parallax measurements made with Hipparcos astrometry satellite, α Arietis is about 65.8 light-years from Earth. It is a giant star that may host an orbiting planet with a mass greater than Jupiter.

Alpha Caeli is a double star system in the constellation Caelum.
Alpha Caeli A is an F-type main sequence star with a stellar classification of F2V and an apparent magnitude of +4.44. It has 1.48 times the mass of the Sun and 1.3 times the solar radius. The projected rotational velocity at the stellar equator is 47.8 km/s. It is suspected of being a Delta Scuti variable star.
The companion is a spectral class M0.5V red dwarf star with absolute magnitude 9.80. It is a UV Ceti variable star that undergoes random increases in luminosity. This star is currently separated from the primary by an angle of 6.6 arcseconds, which indicates an orbit with a semimajor axis whose expected value is 206 AU.
Alpha Caeli is approximately 65.7 light years from Earth and is an estimated 900 million years old. The space velocity components of this system are U = 10, V = 6 and W = -10 km/s. It is orbiting the Milky Way galaxy at an average distance of 8.006 kpc from the core and with an orbital eccentricity of 0.07. This orbit lies close to the galactic plane, and the system travels no more than 0.05 kpc above or below this plane.

Alpha Camelopardalis is a star in the constellation Camelopardalis, with an apparent visual magnitude of 4.301. It is the third brightest star in this not very prominent circumpolar constellation, the first and second brightest stars being β Camelopardalis and CS Camelopardalis, respectively.It is the farthest constellational star, with a distance of 6000 light-years from Earth.
This star has a stellar classification of O9.5Iae, with the 'Ia' indicating that it is an O-type luminous supergiant and the 'e' showing that there are emission lines in its spectrum. It is a massive star with 43 times the mass of the Sun and 37 times the Sun's radius. The effective temperature of the outer envelope is 27,700 K; much hotter than the Sun's effective temperature of 5,778 K, giving it the characteristic blue hue of an O-type star. It is emitting 680,000 times the luminosity of the Sun and is a weak X-ray emitter.
This star shows multiple patterns of variability. It may be a non-radial pulsating variable star, which is causing changes in the spectrum being emitted by the photosphere.

Alpha Cassiopeiae is a second magnitude star in the constellation Cassiopeia, with the traditional name Schedar, sometimes spelt Shedir. Though listed as the alpha star by Johann Bayer, Schedar's visual brightness closely rivals the beta star in the constellation, Caph. Depending on which passband is used, α Cas may be marginally brighter or dimmer than β Cas. However, recent calculations from the All-Sky catalog indicate that Schedar is the brightest in Cassiopeia, with a visual magnitude of 2.240. With Schedar located farther away from Earth than Caph, at 228 light years versus 54, Schedar is almost 18 times brighter than its rival insofar as intrinsic brightness is concerned.

Alpha Cephei is a second magnitude star in the constellation of Cepheus near the northern pole. The star is relatively close to Earth at only 49 light years. It has the traditional name Alderamin, an Arabic name meaning "the right arm".

Alpha Comae Berenices is a star in the constellation Coma Berenices. Although it has the Bayer designation "alpha", at magnitude 4.32 it is actually fainter than Beta Comae Berenices. It has the traditional name Diadem. It is said to represent the crown worn by Queen Berenice. A name occasionally seen is Al Dafirah, from the Arabic الضفيرة ađ̧-đ̧afīrah "the braid".
In Chinese, 太微左垣, meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of α Comae Berenices, η Virginis, γ Virginis, δ Virginis and ε Virginis. Consequently, α Comae Berenices itself is known as 太微左垣五, representing 東上將, meaning The First Eastern General. 東上將, westernized into Shang Tseang, but the name Shang Tseang was designated for "v Comae Berenices" by R.H. Allen and the meaning is "a Higher General"

Alpha Coronae Borealis is a binary star in the constellation Corona Borealis. It is located about 75 light years from the Solar System.

Alpha Crucis is the brightest star in the constellation Crux, the Southern Cross, and, at a combined visual magnitude 0.77, is the 13th brightest star in the night sky. Acrux is the southernmost first-magnitude star, just a little more southerly than Alpha Centauri.

Alpha Ophiuchi is the brightest star in the constellation Ophiuchus. It has the traditional name Ras Alhague, often condensed to Rasalhague.
Alpha Ophiuchi is a binary star system with an orbital period of about 8.62 years. The orbital parameters were only poorly known until 2011 when observations using adaptive optics produced a better orbital fit, allowing the individual masses of the two components to be determined. The primary component, Alpha Ophiuchi A, has a mass of about 2.4 times the mass of the Sun, while the secondary, Alpha Ophiuchi B, has 0.85 solar masses. Estimates of the mass of the primary by other means range from a low of 1.92 to 2.10 solar masses, up to 2.84 or even 4.8 solar masses. The mass of the secondary suggests that it has a stellar classification in the range K5V to K7V, which indicates it is a main sequence star that is still generating energy by the thermonuclear fusion of hydrogen at its core. The pair reached periastron passage, or closest approach, around April 19, 2012, when they had an angular separation of 50 milliarcseconds.

Peacock is a star in the southern constellation Pavo, near the shared border with the Telescopium constellation. Its name was assigned by Her Majesty's Nautical Almanac Office in the late 1930s during the creation of the Air Almanac, a navigational almanac for the Royal Air Force. Of the fifty-seven stars included in the new almanac, two had no classical names: Epsilon Carinae and Alpha Pavonis. The RAF insisted that all of the stars must have names, so new names were invented. Alpha Pavonis was named "Peacock" whilst Epsilon Carinae was called "Avior".
At an apparent magnitude of 1.94, this is the brightest star in Pavo. Based upon parallax measurements, this star is about 179 light-years distant from the Earth. It has an estimated six times the Sun's mass and 5–6 times the Sun's radius, but 2,200 times the luminosity of the Sun. However, Tetzlaff et al. suggest a much higher mass of 9 times the mass of the Sun. The effective temperature of the photosphere is 18,000 K, which gives the star a blue-white hue. A stellar classification of B2 IV suggests it is a subgiant star that has begun to evolve from the main sequence with the exhaustion of the hydrogen at its core.

Alpha Pegasi is the third brightest star in the constellation Pegasus and one of the four stars in the asterism known as the Great Square of Pegasus. It has the traditional name Markab, which comes from an Arabic word مركب markab, "the saddle of the horse", or is mistranscription of Mankib comes from an Arabic phrase منكب الفرس Mankib al-Faras, " the Shoulder of the Horse" for β Pegasi.
Markab has a stellar classification of B9 III, indicating that it is a B-type giant star that has exhausted the hydrogen at its core and has evolved beyond the main sequence. It is rotating rapidly, with a projected rotational velocity of 125 km/s giving a lower bound on the azimuthal velocity along the star's equator. The effective temperature of the photosphere is nearly 10,000 K and the star has expanded to nearly five times the radius of the Sun.

Alpha Persei is the brightest star in the northern constellation of Perseus, just outshining the constellation's best known star, Algol. Known by the traditional names Mirfak and Algenib, it is a circumpolar star when viewed from the latitude of New York City or higher. It has an apparent visual magnitude of 1.8, placing it among the brightest stars in the sky. Mirfak lies in the midst of a cluster of stars eponymously named the Alpha Persei Cluster, or Melotte 20, which is easily visible in binoculars and includes many of the fainter stars in the constellation. The distance to this star has been determined using the parallax technique, putting it 510 light-years away.

Alpha Ursae Majoris is the second-brightest star in the constellation of Ursa Major. It has the traditional name Dubhe, and a rarer name Ak.
This star forms part of the Big Dipper, and is the northern of the 'pointers', the two stars of Ursa Major which point towards Polaris, the North Star. Dubhe is about 123 light years away and is a giant star that has evolved away from the main sequence after consuming the hydrogen at its core. It is a spectroscopic binary with a main sequence companion α UMa B that has a stellar classification of K0V. The companion star orbits at a mean separation of about 23 astronomical units and completes an orbit every 44.4 years. More than 8,000 AU distant from this pair is a second binary system that includes an F-type star, making this a four star system.
Although it is part of the constellation of Ursa Major, it does not form part of the Ursa Major Moving Group of stars that have a common motion through space.

Alphard is the brightest star in the constellation Hydra. The name Alphard is from the Arabic الفرد, "the solitary one", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In ancient China it formed part of an asterism called the "red bird". The European astronomer Tycho Brahe dubbed it Cor Hydræ, the heart of the snake.
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, it was designated Soheil al Fard, which was translated into Latin as Soheil Solitarius, meaning the bright solitary one.
In Chinese, 星宿, meaning Star, refers to an asterism consisting of Alphard, τ¹ Hydrae, τ² Hydrae, ι Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428. Consequently, Alphard itself is known as 星宿一, "the First Star of Star".

Altair is the brightest star in the constellation Aquila and the twelfth brightest star in the night sky. It is currently in the G-cloud. Altair is an A-type main sequence star with an apparent visual magnitude of 0.77 and is one of the vertices of the Summer Triangle. It is 16.7 light-years from Earth and is one of the closest stars visible to the naked eye.
Altair rotates rapidly, with a velocity at the equator of approximately 286 km/s. A study with the Palomar Testbed Interferometer revealed that Altair is not spherical, but is flattened at the poles due to its high rate of rotation. Other interferometric studies with multiple telescopes, operating in the infrared, have imaged and confirmed this phenomenon.

Arcturus of the constellation Boötes is the brightest star in the northern celestial hemisphere. With a visual magnitude of −0.04, it is the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. It is a relatively close star at only 36.7 light-years from Earth, and, together with Vega and Sirius, one of the most luminous stars in the Sun's neighborhood.
Arcturus is a type K1.5 IIIpe orange giant star, with an absolute magnitude of −0.30. It has likely exhausted its hydrogen from its core and is currently in its active hydrogen shell burning phase. It will continue to expand before entering horizontal branch stage of its life cycle.

Barnard's Star is a very low-mass red dwarf star about six light-years away from Earth in the constellation of Ophiuchus, the Snake-holder. Barnard's Star is the fourth-closest known individual star to the Sun, after the three components of the Alpha Centauri system, and the closest star in the Northern Hemisphere. Despite its proximity, Barnard's Star, at a dim apparent magnitude of about nine, is not visible with the unaided eye; however, it is much brighter in the infrared than it is in visible light. The star is named for American astronomer E.E. Barnard. He was not the first to observe the star, but in 1916 he measured its proper motion as 10.3 arcseconds per year, which remains the largest-known proper motion of any star relative to the Solar System.
Barnard's Star has been the subject of much study, and it has probably received more attention from astronomers than any other class M dwarf star due to its proximity and favorable location for observation near the celestial equator. Historically, research on Barnard's Star has focused on measuring its stellar characteristics, its astrometry, and also refining the limits of possible extrasolar planets.

Bellatrix, also known by its Bayer designation Gamma Orionis, is the third brightest star in the constellation Orion, 5° right of the red giant α Ori. Just between the 1st and 2nd magnitude, it is the 27th brightest star in the night sky.

Beta Andromedae is the Bayer designation for a prominent star in the northern constellation of Andromeda. It has the traditional name Mirach, which is also spelled Merach, Mirac, Mirak. β Andromedae is located northeast of the Great Square of Pegasus and is theoretically visible to all observers north of 54° S. The galaxy NGC 404, also known as Mirach's Ghost, is visible seven arc-minutes away.
This star has an average apparent visual magnitude of 2.05, which makes it the brightest star in the constellation. However, the luminosity varies slightly from magnitude +2.01 to +2.10. Based upon parallax measurements, it is located at a distance of roughly 197 light-years from Earth. The apparent magnitude of this star is reduced by 0.06 from extinction caused by the gas and dust along the line of sight.

Beta Aquarii is a double star in the constellation Aquarius. It has the traditional name Sadalsuud, from an Arabic expression سعد السعود sa‘d al-su‘ūd, the "luck of lucks". Other spellings that are sometimes encountered are Sad es Saud, Sadalsund, and Saad el Sund.
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Nir Saad al Saaoud, which was translated into Latin as Lucida Fortunæ Fortunarum, meaning the brightest of luck of lucks.

Beta Aquilae is a star in the constellation Aquila. It has the traditional name Alshain from the Perso-Arabic term الشاهين aš-šāhīn "the falcon", perhaps by folk etymology from the Persian šāhīn tarāzū, the Persian name for the asterism α, β and γ Aquilae.
In Chinese, 河鼓, meaning River Drum, refers to an asterism consisting of β Aquilae, Altair and γ Aql. Consequently, β Aquilae itself is known as 河鼓一
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Unuk al Ghyrab, which was translated into Latin as Collum Corvi, meaning the crow's neck.
Beta Aquilae has magnitude 3.71 and is of spectral class G8IV. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is approximately 44.7 light years from Earth. It has a 12th magnitude optical companion, β Aquilae B, which is 13 arcseconds away in the sky.

Beta Boötis is the Bayer designation for a star in the northern constellation of Boötes. It has an apparent visual magnitude of 3.5, making it one of the brighter members of the constellation. The traditional name Nakkar or Nekkar for this star is based upon the Arabic name for the constellation. This is a mis-transliteration of the Arabic بقّار baqqār "cattle driver", the Arabic letters b and n differing only in the placement of the dot. In the modern constellation, it marks the head of Boötis the herdsman. Based upon parallax measurements, this star is approximately 225 light-years from Earth. At that distance, the magnitude of the star is reduced by 0.06 from extinction caused by intervening gas and dust.
Nakkar has more than three times the mass of the Sun and greater than 21 times the Sun's radius. At the estimated age of 240–251 million years, it has evolved into a giant star with a stellar classification of G8 IIIa. The star is radiating around 170–194 times as much luminosity as the Sun from its outer envelope at an effective temperature of 4,932 K. This heat gives it the yellow-hued glow of a G-type star.

Beta Cancri is the brightest star in the constellation Cancer. It has the traditional name Tarf or Al Tarf, certainly a derivation from Arabic الطرف aṭ-ṭaraf "the eye" or طرفة aṭ-ṭarfah "the glance". It is approximately 290 light years from Earth.
This is an orange K-type giant, about 49 times the radius of the Sun, with an apparent magnitude of +3.50 and absolute magnitude of -1.25. It has a faint, fourteenth magnitude, red dwarf companion star located 29 arcseconds away. A planet, Beta Cancri b, was discovered on May 13, 2014.

Beta Canis Majoris is a star in the southern constellation of Canis Major, the 'greater dog', and is located at a distance of about 500 light-years from the Earth. In the modern constellation it lies at the position of the dog's head. It has the traditional name Murzim, Al-Murzim or Mirzam, which is derived from the Arabic for 'The Herald', and probably refers to its position, heralding Sirius in the night sky.
In Chinese, 軍市, meaning Market for Soldiers, refers to an asterism consisting of β Canis Majoris, ν³ Canis Majoris, 15 Canis Majoris, π Canis Majoris, ο¹ Canis Majoris and ξ¹ Canis Majoris. Consequently, β Canis Majoris itself is known as 軍市一. From this Chinese name arose the name Kuen She.
The Dunhuang Star Chart noted β Canis Majoris as Yeji "Pheasant Cock", though was located about 10 degrees too far north of its correct position.

Beta Cassiopeiae is a Delta Scuti variable star in the constellation Cassiopeia. It is a subgiant or giant star belonging to the spectral class F2. The white star of second magnitude has an absolute magnitude of +1.16 mag. It has the traditional name Caph, from the Arabic word كف kaf, "palm", also known as Al Sanām al Nākah. Another Arabic name is al-Kaff al-Khadib.

Beta Cephei is a third magnitude star in the constellation Cepheus. It has the traditional name Alfirk, meaning "The Flock" This star, along with α Cep and η Cep, were Al Kawākib al Firḳ, meaning "the Stars of The Flock" by Ulug Beg. Beta Cephei is the prototype of the Beta Cephei variable stars.

Beta Draconis is the third brightest star in the northern circumpolar constellation of Draco. It has the traditional name Rastaban, which has also been used for Gamma Draconis. With an apparent visual magnitude of 2.79, it is bright enough to be easily seen with the naked eye. Based upon parallax measurements from the Hipparcos astrometry satellite, it lies at a distance of about 380 light-years from Earth.
Compared to the Sun, this is an enormous star with six times the mass and roughly 40 times the radius. At this size, Beta Draconis is emitting about 950 times the luminosity of the Sun from its outer envelope at an effective temperature of 5,160 K, giving it the yellow hue of a G-type star. The spectrum matches a stellar classification of G2 Ib–IIa, with the luminosity class notation Ib–IIa indicating it lies part way between the bright giant and supergiant stages of its stellar evolution. It is about 67 million years old.
This is a binary star system, with a binary star designation of ADS 10611, in which the supergiant is orbited by a dwarf companion once every four millennia or so.

Beta Ophiuchi is a star in the equatorial constellation of Ophiuchus. It has the traditional names Celbalrai, which comes from the Arabic كلب الراعي kalb al-rā‘ī meaning "shepherd dog". It is also called Cheleb, Kelb Alrai, or sometimes just Alrai. The apparent visual magnitude of this star is 2.7, which is readily visible to the naked eye even from urban skies. The distance to this star can be estimated using parallax measurements, yielding a value of 81.8 light-years.
This is a giant star with a stellar classification of K2 III. Although it is only 13% greater in mass than the Sun, it has reached a stage in its evolution where the atmosphere has expanded to about 12 times the Sun's radius and is radiating 63 times the luminosity of the Sun. Its outer envelope is relatively cool with an effective temperature of 4,467 K, giving it the orange hue typical of K-type stars. Like some other K-type giants, β Ophiuchi has been found to vary very slightly in brightness,
Cebalrai is a member of the thin disk population.

Beta Pegasi is a red giant star in the constellation Pegasus. The apparent visual magnitude of this star averages 2.42, making it the second brightest star in the constellation after Epsilon Pegasi. Its traditional name is Scheat, a name that has also been used for Delta Aquarii. According to Richard H. Allen, this name comes from the Arabic Al Sā'id for 'the upper arm', or from Sa'd. Arabian astronomers named it Mankib al Faras, meaning the "Horse's shoulder". It forms the upper right corner of the Great Square of Pegasus, a prominent rectangular asterism.
Based upon parallax measurements, Beta Pegasi is located about 196 light-years from the Earth. It is unusual among bright stars in having a relatively cool surface temperature compared to stars like the Sun. This star has a stellar classification of M2.3 II-III, which indicates the spectrum has characteristics partway between a bright giant and a giant star. It has expanded until it is some 95 times as large, and has a total luminosity of 1500 times that of the Sun. The effective temperature of the star's outer envelope is about 3,700 K, giving the star the characteristic orange-red hue of an M-type star.

Beta Pictoris is the second brightest star in the constellation Pictor. It is located 63.4 light years from our solar system, and is 1.75 times as massive and 8.7 times as luminous as the Sun. The Beta Pictoris system is very young, only 8–20 million years old, although it is already in the main sequence stage of its evolution. Beta Pictoris is the title member of the Beta Pictoris moving group, an association of young stars which share the same motion through space and have the same age.
Beta Pictoris shows an excess of infrared emission compared to normal stars of its type, which is caused by large quantities of dust and gas near the star. Detailed observations reveal a large disk of dust and gas orbiting the star, which was the first debris disk to be imaged around another star. In addition to the presence of several planetesimal belts and cometary activity, there are indications that planets have formed within this disk and that the processes of planet formation may still be ongoing. Material from the Beta Pictoris debris disk is thought to be the dominant source of interstellar meteoroids in our solar system.

Beta Tauri is the second brightest star in the constellation Taurus, with an apparent magnitude of 1.68. Ptolemy considered Beta Tauri to be shared by Auriga, and Bayer assigned it a designation in both constellations: Beta Tauri and Gamma Aurigae. When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use. The star has the traditional name Elnath—a reference to "the butting" of the bull's horns.

Beta Ursae Majoris is a star in the northern circumpolar constellation of Ursa Major. It has the traditional name Merak.
The apparent visual magnitude of this star is +2.37, which means it is readily visible to the naked eye. It is more familiar to northern hemisphere observers as one of the "pointer stars" in the Big Dipper, or "The Plough" in England, which is a prominent asterism of seven stars that forms part of the larger constellation. Extending an imaginary straight line from this star through the nearby Alpha Ursae Majoris extends to Polaris, the north star.

Beta Ursae Minoris is the brightest star in the bowl of the "Little Dipper", and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. It has the traditional name Kochab. Kochab is 16 degrees from Polaris and has an apparent visual magnitude of 2.08. The distance to this star can be deduced from the parallax measurements made during the Hipparcos, yielding a value of 130.9 light-years.
Kochab and its neighbor Pherkad are both naked eye stars and are sometimes referred to as the "Guardians of the Pole" or the "Indestructibles". They served as twin pole stars, Earth's North pole stars, from 1500 BC until 500 AD. Neither star was as proximitous to the celestial north pole as Polaris is now. Due to precession of the equinoxes, the previous holder of the title was Thuban, and the next was the present-day Polaris. This succession of pole stars is a result of earth's precessional motion.
Amateur astronomers can use Kochab as a very precise guide for setting up a telescope, as the celestial north pole is located 43 arcminutes away from Polaris, very close to the line connecting Polaris with Kochab.

Betelgeuse, also known by its Bayer designation Alpha Orionis, is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion. Distinctly reddish, it is a semiregular variable star whose apparent magnitude varies between 0.2 and 1.2, the widest range of any first-magnitude star. Betelgeuse is one of three stars that make up the Winter Triangle, and it marks the center of the Winter Hexagon. The star's name is derived from the Arabic يد الجوزاء Yad al-Jauzā', meaning "the hand of Orion". The Arabic character for Y was misread as B by medieval translators, creating the initial B in Betelgeuse.
The star is classified as a red supergiant of spectral type M2Iab and is one of the largest and most luminous observable stars. If Betelgeuse were at the center of the Solar System, its surface would extend past the asteroid belt, possibly to the orbit of Jupiter and beyond, wholly engulfing Mercury, Venus, Earth and Mars. Estimates of its mass are poorly constrained, but range from 5 to 30 times that of the Sun. Its distance from Earth was estimated in 2008 at 640 light-years, yielding a mean absolute magnitude of about −6.02.

Canopus is the brightest star in the southern constellation of Carina, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.65.
Canopus is a supergiant of spectral type F. Canopus is essentially white when seen with the naked eye. It is located in the far southern sky, at a declination of −52° 42' and a right ascension of 06h24.0m.
Its name comes from the mythological Canopus, who was a navigator for Menelaus, king of Sparta.

Castor is the second brightest star in the constellation Gemini and one of the brightest stars in the night sky. Although it has the Bayer designation "alpha", it is actually fainter than Beta Geminorum. Castor is 49.8 light years away from Earth.

Celaeno is a star in the constellation Taurus and a member of the Pleaides open cluster of stars. Celaeno has been called the "Lost Pleiad" by Theon the Younger. Star gazers often only see six of the seven Pleiades sisters with the unaided eye because Celaeno, with an apparent magnitude of +5.45, requires clear, dark skies to be observed.
16 Tauri is a blue-white B-type subgiant with an apparent magnitude of +5.45. It is approximately 430 light years from Earth; about the same distance as the Pleiades. The interstellar extinction of this star is fairly small at 0.05 magnitudes. The projected rotational velocity of the equator is 185 km/s. It is over four times the radius of the Sun and has a surface temperature of 12,800 K.

The Crab Pulsar is a relatively young neutron star. The star is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was widely observed on Earth in the year 1054. Discovered in 1968, the pulsar was the first to be connected with a supernova remnant.
The Crab Pulsar is one of very few pulsars to be identified optically. The optical pulsar is roughly 20 km in diameter and the pulsar "beams" rotate once every 33 milliseconds, or 30 times each second. The outflowing relativistic wind from the neutron star generates synchrotron emission, which produces the bulk of the emission from the nebula, seen from radio waves through to gamma rays. The most dynamic feature in the inner part of the nebula is the point where the pulsar's equatorial wind slams into the surrounding nebula, forming a termination shock. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar into the main body of the nebula.

Delta Aquarii is the third-brightest star in the constellation Aquarius. It has the traditional name Skat, which has also been used for Beta Pegasi. The apparent visual magnitude is 3.3, which can be seen with the naked eye. The distance to this star is estimated as 160 light-years based upon parallax measurements.

Delta Cancri is an orange giant star approximately 180 light-years away in the constellation Cancer. It has the traditional name Asellus Australis which in Latin means "southern donkey colt". It also has the longest of all known star names, Arkushanangarushashutu, derived from ancient Babylonian which means "the southeast star in the Crab".
In Chinese, 鬼宿, meaning Ghost, refers to an asterism consisting of δ Cancri, θ Cancri, η Cancri and γ Cancri. Consequently, δ Cancri itself is known as 鬼宿四
Since it is near the ecliptic, it can be occulted by the Moon and very rarely by planets.

Delta Canis Majoris is a star in the constellation Canis Major. It has the traditional name Wezen or Wesen. It is a yellow-white F-type supergiant with an apparent magnitude of +1.83. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.

Delta Cassiopeiae is a star in the northern circumpolar constellation of Cassiopeia. It has the traditional names Ksora and Ruchbah, derived from the Arabic word ركبة rukbah meaning "knee". It is not to be confused with Alpha Sagittarii, which also is called Ruchbah or Rukbat.
In Chinese, 閣道, meaning Flying Corridor, refers to an asterism consisting of δ Cassiopeiae, ι Cassiopeiae, ε Cassiopeiae, θ Cassiopeiae, ν Cassiopeiae and ο Cassiopeiae. Consequently, δ Cassiopeiae itself is known as 閣道三

Delta Draconis is a yellow star in the constellation Draco. It has the traditional names Aldib, Altais and Nodus Secundus. This star has an apparent visual magnitude of 3.0, making it easily visible to the naked eye. Parallax measurements with the Hipparcos satellite yield a distance estimate of 97.4 light-years from Earth.

Delta Geminorum is a star in the constellation Gemini. It has the traditional name Wasat, which comes from the Arabic word for "middle".
It has an apparent visual magnitude of +3.53, allowing it to be seen with the naked eye. Wasat is only two-tenths of a degree south of the ecliptic, and therefore is occasionally occulted by the Moon and, more rarely, by a planet. The last occultation by a planet was by Saturn on June 30, 1857, and the next will be by Venus on August 12, 2420. In 1930, the dwarf planet Pluto was discovered about 0.5° to the east of this star by American astronomer Clyde Tombaugh.
In Chinese, 天樽, meaning Celestial Wine Cup, refers to an asterism consisting of δ Geminorum, 57 Geminorum and ω Geminorum. Consequently, δ Geminorum itself is known as 天樽二. From this Chinese name, the name Ta Tsun has appeared.

Delta Leonis is a star in the zodiac constellation of Leo. It has the traditional names Zosma and Duhr. Rare spellings include Zozca, Zosca, Zubra, and Dhur. The name Zosma means girdle in ancient Greek, referring to the star's location in its constellation, on the hip of the lion. Based upon parallax measurements, it lies at a distance of about 58.4 light-years from the Earth.

Delta Ursae Majoris is the Bayer designation for a star in the northern circumpolar constellation of Ursa Major. It has the traditional names Megrez, and Kaffa. Megrez has an apparent magnitude of +3.3, making it the dimmest of the seven stars in the Big Dipper asterism. Parallax measurements yield a distance estimate of 58.4 light-years from Earth.
Megrez has 63% more mass of the Sun and is about 1.4 times the Sun's radius. It has a stellar classification of A3 V, which means it is an A-type main sequence star that is generating energy at its core through the nuclear fusion of hydrogen. It shines at 14 times the luminosity of the Sun, with this energy being emitted from its outer envelope at an effective temperature of 9,480 K. This gives it the white hue typical of an A-type star.
This star has an excess emission of infrared radiation, indicating the presence of circumstellar matter. This forms a debris disk around an orbital radius of 16 Astronomical Units from the star. This radius is unusually small for the estimated age of the disk, which may be explained by drag from the Poynting–Robertson effect causing the dust to spiral inward.

Deneb is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars. However, its exact distance has been difficult to calculate, so it is anywhere between 54,000 and 196,000 times as luminous as the sun.
Other names include Arided and Aridif, but these have fallen out of use.

Denebola is the third brightest star in the zodiac constellation of Leo. It is an A-type main sequence star with 75% more mass than the Sun and twelve times the Sun's luminosity. Based on parallax measurements from the Hipparcos astrometry satellite, the star is at a distance of about 36 light-years from Earth. Its apparent visual magnitude is 2.14, making it readily visible to the naked eye. Denebola is a Delta Scuti type variable star, meaning its luminosity varies very slightly over a period of a few hours.

Electra, also cataloged as 17 Tauri, is a blue-white giant star in the constellation of Taurus. The star is one of the nine brightest stars in the Pleiades open cluster. The most visible stars in this group are named for the Seven Sisters of Greek mythology.
The star has an apparent brightness of 3.72, the third brightest of the stars in the group. Electra belongs to the spectral class B6 IIIe and is approximately 370 light years from the Sun. Electra is one of the four Pleiades stars that is classed as a giant; one that is starting to expand as the internal hydrogen fuel in the core is exhausted.
The projected rotational velocity of this star is 181 km/s, making it a fast rotator. This is the velocity component of the star's equatorial rotation along the line of sight to the Earth. The estimated inclination of the star's pole is 46.8° ± 1.6, giving it a true equatorial rotational velocity of 320 ± 18 km/s. The rapid rotation rate of this star flattens the poles and stretch the equator. This makes the surface gravity of the star non-uniform and causes temperature variation. This effect is known as gravity darkening, because it results in a variation of radiation by latitude.

Epsilon Aquarii is the Bayer designation for a star in the equatorial zodiac constellation of Aquarius. It has an the traditional name Albali and is visible to the naked eye with an apparent visual magnitude of 3.77. The distance to this star can be determined from parallax measurements, yielding an estimated value of around 208 light-years from Earth. Epsilon Aquarii is an A-type main sequence star with a stellar classification of A1 V.

Epsilon Aurigae is the Bayer designation for a star in the northern constellation of Auriga. It is traditionally known as Almaaz, Haldus, or Al Anz. Epsilon Aurigae is an unusual eclipsing binary system comprising an F0 supergiant and a companion which is generally accepted to be a huge dark disk orbiting an unknown object, possibly a binary system of two small B-type stars. About every 27 years, Epsilon Aurigae's brightness drops from an apparent visual magnitude of +2.92 to +3.83. This dimming lasts 640–730 days. In addition to this eclipse, the system also has a low amplitude pulsation with a non-consistent period of around 66 days. The distance to the system is still a subject of debate, but modern estimates place it approximately 2,000 light years from Earth.
Epsilon Aurigae was first suspected to be a variable star when German astronomer Johann Heinrich Fritsch observed it in 1821. Later observations by Eduard Heis and Friedrich Wilhelm Argelander reinforced Fritsch's initial suspicions and attracted attention to the star. Hans Ludendorff, however, was the first to study it in great detail.

Epsilon Carinae is a star in the southern constellation of Carina. It is also known by the name Avior. At apparent magnitude +1.86 it is one of the brightest stars in the night sky, but is not visible from the northern hemisphere.
Epsilon Carinae is a double star located roughly 560–660 light-years away from the Earth. Measurements during the Hipparcos mission give the pair an angular separation of 0.46 arcseconds with a difference in magnitude of 2.0. At their estimated distance, this angle is equivalent to a physical separation of around 4 Astronomical Units. This pair may form an eclipsing binary system with a period of 785 days, resulting in a magnitude change of 0.12 during each eclipse.
The primary component has an apparent visual magnitude of 2.2, which by itself would still make it the third brightest star in the constellation. It is an evolved giant star with a stellar classification of K0 III. However, examination of the ultraviolet flux from this star suggests it may instead be of spectral type K7. The fainter secondary companion has an apparent visual magnitude of 4.1, which, if it were a solitary star, would be bright enough to be seen with the naked eye.

Epsilon Eridani is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows it to be viewed from most of Earth's surface. At a distance of 10.5 light years, it has an apparent magnitude of 3.73. It is the third closest individual star or star system visible to the unaided eye and was the closest star known to host a planet until the unconfirmed discovery of Alpha Centauri Bb. Its age is estimated at less than a billion years. Because of its youth, Epsilon Eridani has a higher level of magnetic activity than the present-day Sun, with a stellar wind 30 times as strong. Its rotation period is 11.2 days at the equator. Epsilon Eridani is smaller and less massive than the Sun, and has a comparatively lower level of elements heavier than helium. It is a main-sequence star of spectral class K2, which means that energy generated at the core through nuclear fusion of hydrogen is emitted from the surface at a temperature of about 5,000 K, giving it an orange hue.
The motion of Epsilon Eridani along the line of sight to Earth, known as the radial velocity, has been regularly observed for more than twenty years.

Epsilon Indi is a star system approximately 12 light-years away from the Earth in the constellation of Indus consisting of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf and ε Indi Bb a late T dwarf separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.

Epsilon Pegasi is the brightest star in the northern constellation of Pegasus. It has the traditional name Enif. The name Enif is derived from the Arabic word for nose, due to its position as the muzzle of Pegasus. With an apparent visual magnitude of 2.4, this is a second-magnitude star that is readily visible to the naked eye. The distance to this star can be estimated using parallax measurements from the Hipparcos astrometry satellite, yielding a value of around 690 light-years.
Other traditional names for the star include Fom al Feras, Latinised to Os Equi. In Chinese, 危宿, meaning Rooftop, refers to an asterism consisting of ε Pegasi, α Aquarii and θ Peg. Consequently, ε Pegasi itself is known as 危宿三

Epsilon Ursae Majoris is the brightest star in the constellation Ursa Major, and at magnitude 1.76 is the thirty-first brightest star in the sky. It has the traditional name Alioth. It is the star in the tail of the bear closest to its body, and thus the star in the handle of the Big Dipper closest to the bowl. It is also a member of the large and diffuse Ursa Major moving group. Historically, the star was frequently used in celestial navigation in the maritime trade, because it is listed as one of the 57 navigational stars.

Eta Boötis is a star in the constellation Boötes. It has the traditional names Muphrid and Saak, and the Flamsteed designation 8 Boötis. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
The name Muphrid is from the Arabic مفرد الرامح mufrid ar-rāmiħ "the one of the lancer". In Chinese, 右攝提, meaning "the Right Conductor", refers to an asterism consisting of Eta Boötis, Tau Boötis and Upsilon Boötis. Consequently, Eta Boötis itself is known as 右攝提一. In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Ramih al Ramih, which was translated into Latin as Lancea Lanceator, possibly meaning the lance of the lancer.
This star is a subgiant that has begun the process of evolving from a main sequence star into a red giant. It has about 1.7 times the mass of the Sun and 2.7 times the Sun's radius. The estimated age of this star is about 2.7 billion years. Based on its spectra, Eta Boötis has a significant excess of elements heavier than helium. In fact the ratio of iron to hydrogen is considered close to the upper limit for dwarf stars in the galactic disk.

Eta Canis Majoris is a star in the constellation Canis Major. It has the traditional name Aludra. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
The name Aludra originates from the Arabic: عذرا al-‘aðrā "the virgin". This star, along with ε CMa, δ CMa and ο² CMa, were Al ʽAdhārā, the Virgins.
In Chinese, 弧矢, meaning Bow and Arrow, refers to an asterism consisting of η Canis Majoris, δ Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris, κ Canis Majoris and π Puppis. Consequently, δ Canis Majoris itself is known as 弧矢二

Eta Ursae Majoris is a star in the constellation Ursa Major. It has the traditional names Alkaid and Benetnash. Alkaid is the most eastern star in the Big Dipper asterism. However, unlike most stars of the Big Dipper, it is not a member of the Ursa Major moving group. With an apparent visual magnitude of +1.84, it is the third brightest star in the constellation and one of the brightest stars in the night sky.

This is a 10 million year old B-type main sequence star with a stellar classification of B3 V. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It has six times the mass of the Sun and 3.4 times the Sun's radius. Eta Ursae Majoris is radiating around 1,350 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of about 16,823 K, giving it the blue-white hue of a B-type star. This star is an X-ray emitter with a luminosity of 9.3 × 10²⁸ erg s–1.

Fomalhaut is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. It is a class A star on the main sequence approximately 25 light-years from Earth as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk. Fomalhaut, K-type star TW Piscis Austrini and M-type star LP 876-10 constitute a trinary system.
Fomalhaut holds a special significance in extrasolar planet research, as it is the center of the first stellar system with an extrasolar planet candidate imaged at visible wavelengths. The image was published in Science in November 2008. Fomalhaut is the third brightest star known to have a planetary system, after Pollux and the Sun.

GJ 1214 is a dim M4.5 red dwarf in the constellation Ophiuchus with an apparent magnitude of 14.7. It is located at a distance of approximately 47 light years from Earth. It is about one-fifth as large as the Sun with a surface temperature estimated to be 3,000 K. Its luminosity is only 0.003% that of the Sun.
The estimate for the stellar radius is 15% larger than predicted by theoretical models. It also shows a 1% intrinsic variability in the near-infrared probably caused by stellar spots.

Gamma Aquilae is a star in the constellation Aquila. It has the traditional name Tarazed. This star has an apparent visual magnitude of 2.712, so it is readily visible to the naked eye at night. Parallax measurements place it at a distance of 395 light-years from Earth.

Gamma Boötis is a star in the constellation Boötes. It has the traditional name Seginus of uncertain origin. It was listed as Haris in Bečvář.

Gamma Capricorni is a giant star in the constellation Capricornus. It has the traditional name Nashira, which comes from the Arabic سعد ناشرة - sa'd nashirah for "the lucky one" or "bearer of good news".
In Chinese, 壘壁陣, meaning Line of Ramparts, refers to an asterism consisting of γ Capricorni, κ Capricorni, ε Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, λ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, γ Capricorni itself is known as 壘壁陣三
Because it is near the ecliptic, γ Capricorni can be occulted by the Moon, and by planets.
γ Capricorni is a blue-white A-type giant star with a mean apparent magnitude of +3.69. It is approximately 139 light years from Earth. It is classified as an Alpha2 Canum Venaticorum type variable star and its brightness varies by 0.03 magnitudes.

Gamma Cassiopeiae is the Bayer designation for a star in the northern circumpolar constellation of Cassiopeia. Although it is a fairly bright star with an apparent visual magnitude of 2.47, it has no traditional Arabic or Latin name. However, in Chinese, it has the name Tsih, derived from the word 策, meaning "the whip". It is located at the center of the distinctive "W" shape that forms the constellation's asterism. American astronaut Virgil Ivan "Gus" Grissom nicknamed the star Navi after his own middle name spelled backwards. The star was used as an easily identifiable navigational reference point during space missions. Based upon parallax measurements made by the Hipparcos satellite, this star is located at a distance of roughly 550 light-years from Earth.

Gamma Corvi is the brightest star in the southern constellation of Corvus, having an apparent visual magnitude of 2.6. Its traditional name is Gienah, which it shares with Epsilon Cygni. The name "Gienah Corvi", or "Gienah Ghurab", may be used to distinguish it from this star in Cygnus. The distance to this star has been measured directly using the parallax technique, yielding an estimated 154 light-years from Earth.

Gamma Cygni is the Bayer designation for a star in the northern constellation Cygnus, forming the intersection of an asterism of five stars called the Northern Cross. It has the traditional name Sadr, which name comes from the Arabic word صدر şadr, "chest", the same word which gave rise to the star Schedar. In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Sadr al Dedjadjet, which was translated into Latin as Pectus Gallinǣ, meaning the hen's chest.
In Chinese, 天津, meaning Celestial Ford, refers to an asterism consisting of γ Cygni, δ Cygni, 30 Cygni, α Cygni, ν Cygni, τ Cygni, υ Cygni, ζ Cygni and ε Cygni. Consequently, γ Cygni itself is known as 天津一.

Gamma Draconis is the Bayer designation for a star in the northern constellation of Draco. It has the traditional name Etamin, Eltanin or Ettanin and the Flamsteed designation 33 Draconis. Despite its gamma designation, it is actually the brightest star in Draco at magnitude 2.4, outshining Rastaban by nearly half a magnitude. Its proximity to the zenith point directly overhead of London has earned it the name "Zenith Star." As for other places, it is relatively easy to locate in the night sky. If one finds Vega, Eltanin is the red star just north-northwest of it.
Eltanin lies around 154.3 light-years away, as determined by parallax measurements from the Hipparcos astrometry satellite. In 1728, while unsuccessfully attempting to measure the parallax of this star, James Bradley discovered the aberration of light resulting from the movement of the Earth. Bradley's discovery confirmed Copernicus' theory that the Earth revolved around the Sun.

Gamma Leonis is a binary star system in the constellation Leo. It has the traditional name Algieba or Al Gieba.

Gamma Ursae Majoris is a star in the constellation Ursa Major It has the traditional name Phad, or Phecda. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Based upon parallax measurements with the Hipparcos astrometry satellite, it is located at distance of around 83.2 light-years.
It is more familiar to most observers in the northern hemisphere as the lower-left star forming the bowl of the Big Dipper, together with Dubhe, Merak and Megrez. Along with four other stars in this well-known asterism, Phecda forms an actual loose, association of stars known as the Ursa Major moving group. Like the other stars in the group, it is a main sequence star not unlike our Sun, although somewhat hotter, brighter and larger.
Gamma Ursae Majoris is an Ae star, which is surrounded by an envelope of gas that is adding emission lines to the spectrum of the star; hence the 'e' suffix in the stellar classification of A0 Ve. It has 2.6 times the mass of the Sun, three times the Sun's radius, and an effective temperature of 9,355 K in its outer atmosphere.

Gamma Ursae Minoris is a star in the northern circumpolar constellation of Ursa Minor. It has the traditional name Pherkad, which derives from the Arabic فرقد farqad "calf", short for aḫfa al farkadayn "the dim one of the two calves", Pherkad and Kochab. Gamma Ursae Minoris is sometimes called Pherkad Major to distinguish it from 11 Ursae Minoris Pherkad Minor. Together with Beta Ursae Minoris, or Kochab, Gamma forms the end of the dipper pan of the "Little Dipper", which is a colloquial name for the constellation. Pherkad and Kochab are sometimes called the "Guardians of the Pole" or the "Indestructibles", as they appear to circle around the north star Polaris as the Earth rotates.
In Chinese, 北極, meaning North Pole, refers to an asterism consisting of γ Ursae Minoris, β Ursae Minoris, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694. Consequently, γ Ursae Minoris itself is known as 北極一, representing 太子, meaning Crown Prince
Gamma Ursae Minoris has apparent magnitude +3.05 and can be readily observed with the naked eye even in a city-lit night sky. Based upon parallax measurements, it is approximately 487 light-years from Earth, giving it an absolute magnitude of –2.84.

Gliese 436 is a red dwarf approximately 33.1 light-years away in the zodiac constellation of Leo. It has an apparent visual magnitude of 10.67, which is much too faint to be seen with the naked eye. However, it can be viewed with even a modest telescope of 2.4 in aperture. In 2004, the existence of a transiting extrasolar planet, Gliese 436b, was verified as orbiting the star. In 2012, the existence of a second planet, UCF-1.01, was also verified.

Gliese 581 is a star of spectral type M3V about 20 light years away from Earth in the constellation Libra. Its estimated mass is about a third of that of the Sun, and it is the 89th closest known star to the Sun. Observations suggest that the star has a planetary system consisting of three planets, designated Gliese 581 b, c and e in order of discovery. Additional outer planets, which received the designations Gliese 581 d, f, and g have been proposed, but the evidence that led to the discovery claims has been shown to be the result of stellar activity mimicking the radial velocity variations due to orbiting planets.
Gliese 581 has been the subject of a "huge amount of attention" in the quest to discover the first habitable extrasolar planet; first for c, and then d and g. Gliese 581 c, the first low-mass extrasolar planet found near a habitable zone, was discovered in April 2007. It has since been shown that under known terrestrial planet climate models, Gliese 581 c is likely to have a runaway greenhouse effect, and hence is probably too hot to be habitable, analogous to Venus.

Gliese 710 is a star in the constellation Serpens Cauda with an apparent visual magnitude of 9.69. It has a stellar classification of K7 Vk, which means it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The mass of this star is about 60% of the Sun's mass and it has an estimated 67% of the Sun's radius. It is a suspected variable star that may vary in magnitude from 9.65–9.69.
This star is currently about 63.8 light-years from Earth, but its proper motion, distance, and radial velocity indicate that it will approach within a very small distance—perhaps under one light year—from the Sun within 1.4 million years, based on past and current Hipparcos data. At closest approach it will be a first-magnitude star about as bright as Antares. The proper motion of Gliese 710 is very small for its distance, meaning it is traveling nearly directly in our line of sight.
In a time interval of ±10 million years from the present, Gliese 710 is the star whose combination of mass and close approach distance will cause the greatest gravitational perturbation of the Solar System.

Gliese 876 is a red dwarf approximately 15 light-years away from Earth in the constellation of Aquarius.
It is the third closest known star to the Sun confirmed to possess a planetary system and the closest such system known to consist of multiple planets. As of 2011, four extrasolar planets have been found to orbit the star.
The planetary system is also notable for the orbital properties of its planets. It is the only known system of orbital companions to exhibit a triple conjunction in the rare phenomenon of Laplace resonance. It is also the first extrasolar system around a normal star with measured coplanarity.
Two of the middle planets are located in the system's habitable zone, however they are giant planets believed to be analogous to Jupiter.

HD 188753 is a hierarchical triple star system approximately 151 light-years away in the constellation of Cygnus, the Swan. In 2005, an extrasolar planet was announced to be orbiting the primary star in the system. Follow-up measurements by an independent group in 2007 did not confirm the planet's existence.

HD 209458 is an 8th magnitude star in the constellation Pegasus. It is very similar to our Sun, and it is classified as a yellow dwarf. Because it is located at a distance of about 150 light years, it is not visible to the unaided eye. With good binoculars or small telescope it should be easily detectable.
In 1999 two teams working independently discovered an extrasolar planet orbiting the star by using the radial velocity planet search method. Soon after the discovery, separate teams led by David Charbonneau and Gregory W. Henry were able to detect a transit of the planet across the surface of the star making it the first known transiting extrasolar planet. The planet received the designation HD 209458 b.
Because the planet transits the star, the star is dimmed by about 2% every 3.5 days making it an extrinsic variable. The variable star designation for HD 209458 is V376 Pegasi. It is the prototype of the variable class "EP" in the General Catalogue of Variable Stars, defined as stars showing eclipses by their planets.

HD 40307 is an orange main-sequence star located approximately 42 light-years away in the constellation of Pictor, taking its primary name from its Henry Draper Catalogue designation. It is calculated to be slightly less massive than the Sun. HD 40307 was observed during or before 1900 as part of the Cape Photographic Durchmusterung. The star has six known planets, three discovered in 2008 and three more in 2012. One of them, HD 40307 g, is a potential super-Earth in the habitable zone, with an orbital period of about 200 days. This object might be capable of supporting liquid water on its surface, although much more information must be acquired before its habitability can be assessed.

IK Pegasi is a binary star system in the constellation Pegasus. It is just luminous enough to be seen with the unaided eye, at a distance of about 150 light years from the Solar System.
The primary is an A-type main-sequence star that displays minor pulsations in luminosity. It is categorized as a Delta Scuti variable star and it has a periodic cycle of luminosity variation that repeats itself about 22.9 times per day. Its companion is a massive white dwarf—a star that has evolved past the main sequence and is no longer generating energy through nuclear fusion. They orbit each other every 21.7 days with an average separation of about 31 million kilometres, or 19 million miles, or 0.21 astronomical units. This is smaller than the orbit of Mercury around the Sun.
IK Pegasi B is the nearest known supernova progenitor candidate. When the primary begins to evolve into a red giant, it is expected to grow to a radius where the white dwarf can accrete matter from the expanded gaseous envelope. When the white dwarf approaches the Chandrasekhar limit of 1.44 solar masses, it may explode as a Type Ia supernova.

Iota Draconis is a star in the northern circumpolar constellation of Draco. It has the traditional name Edasich, a name that comes from the Arabic Al Ḍhiba' of Ulug Beg and the Dresden Globe, or Al dhīlī 'Male hyena' by Kazwini, with Eldsich being recorded in the Century Cyclopedia. A visually unremarkable star of apparent magnitude 3.3, in 2002 it was discovered to have a planet. From parallax measurements, this star is located at a distance of about 101.2 light-years from Earth.

Kepler-10, formerly known as KOI-72, is a sunlike star in the constellation of Draco which lies 173 parsecs from the Earth. Kepler-10 was targeted by NASA's Kepler spacecraft, as it was seen as the first star identified by the Kepler mission that could be a possible host to a small, transiting exoplanet. The star is slightly less massive, slightly larger, and slightly cooler than the Sun; at an estimated 10.4 billion years in age, Kepler-10 is almost 2.6 times the age of the Sun. Kepler-10 is host to a planetary system made up of at least two planets. Kepler-10b, the first undeniably rocky planet, was discovered in its orbit after eight months of observation and announced on January 10, 2011. The planet orbits its star closely, completing an orbit every 0.8 days, and has a density similar to that of iron. The second planet, Kepler-10c, was confirmed on May 23, 2011, based on follow-up observations by the Spitzer Space Telescope. The data shows it has an orbital period of 42.3 days and has a radius more than double that of Earth, but a higher density, making it the largest and most massive rocky planet discovered as of June 2014.

Kepler-11 is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,000 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars. Announced on February 2, 2011, the star system is among the most compact and flattest systems yet discovered. It is the first discovered case of a star system with six transiting planets. All discovered planets are larger than Earth, with the larger ones being about Neptune's size.

Kepler-7 is a star located in the constellation Lyra in the field of view of the Kepler Mission, a NASA operation in search of Earth-like planets. It is home to the fourth of the first five planets that Kepler discovered; this planet, a Jupiter-size gas giant named Kepler-7b, is as light as styrofoam. The star itself is more massive than the Sun, and is nearly twice the Sun's radius. It is also slightly metal-rich, a major factor in the formation of planetary systems. Kepler-7's planet was presented on January 4, 2010 at a meeting of the American Astronomical Society.

Lambda Aquarii is the Bayer designation for a star in the equatorial constellation of Aquarius. It has the obscure traditional names Hydor and Ekkhysis, from the ancient Greek ὕδωρ "water" and ἔκχυσις "outpouring". The apparent visual magnitude of this star is 3.722, which is bright enough to be visible with the naked eye. It is roughly 390 light-years from Earth.
In Chinese, 壘壁陣, meaning Line of Ramparts, refers to an asterism consisting of λ Aquarii, κ Capricorni, ε Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, λ Aquarii itself is known as 壘壁陣七
Lambda Aquarii is a red giant star with a stellar classification of M2.5 III. It is a semiregular variable star star with pulsation periods of 24.5, 32.0, and 49.5 days. This star is on the asymptotic giant branch and is generating energy through the nuclear fusion of hydrogen and helium along concentric shells surrounding an inert core of carbon and oxygen.

Maia is a star in the constellation Taurus. It is the fourth brightest star in the Pleiades open star cluster, after Alcyone, Atlas and Electra, in that order. The name Maia originates with the Greek: Μαῖα and Latin: Maia. She is one of the seven daughters of Atlas and Pleione in Greek mythology—stars which are also included in the Pleaides star cluster. Maia is a blue giant of spectral type B8 III, and a mercury-manganese star.

Merope is a star in the constellation Taurus and a member of the Pleiades star cluster. It is approximately 360 light years from Earth.
Merope is a blue-white B-type subgiant with a mean apparent magnitude of +4.14. Richard Hinckley Allen described the star as lucid white and violet. It has a luminosity of 630 times that of the Sun and a surface temperature of 14,000 kelvins. Merope's mass is roughly 4.5 solar masses and has a radius more than 4 times as great as the Sun's. It is classified as a Beta Cephei type variable star and its brightness varies by 0.01 magnitudes.
Surrounding Merope is the Merope Nebula. Part of the nebula that the Pleiades Cluster is currently passing through, it appears brightest around Merope and is listed in the Index Catalogue as number IC 349.

The Mizar–Alcor stellar sextuple system consists of the quadruple system Mizar and the binary system Alcor.

Mu Arae, often referred to by its designation in the Henry Draper catalogue HD 160691, is a main sequence G-type star around 50 light-years away from Earth in the constellation of Ara. The star has a planetary system with four known planets, three of them with masses comparable to that of Jupiter. The system's innermost planet was the first "hot Neptune or super-Earth" to be discovered.

Mu Cephei, also known as Herschel's Garnet Star, is a red supergiant star in the constellation Cepheus. It is one of the largest and most luminous stars known in the Milky Way. It appears garnet red and is given the spectral class of M2 Ia. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.

Nu Ophiuchi is a star in the equatorial constellation of Ophiuchus. This star is sometimes called by the name Sinistra, meaning left side in Latin. The apparent visual magnitude is +3.3, making it one of the brighter members of this constellation. Based upon parallax measurements made during the Hipparcos mission, this star is located about 151 light-years from Earth.
In China, the star is part of 天市左垣, meaning Left Wall of Heavenly Market Enclosure. The stars in this group include ν Ophiuchi, δ Herculis, λ Herculis, μ Herculis, ο Herculis, 112 Herculis, ζ Aquilae, θ¹ Serpentis, η Serpentis, ξ Serpentis and η Ophiuchi. Consequently, ν Ophiuchi itself is known as 天市左垣九, and together with ζ Capricorni represents the state Yan in the Twelve States constellation.
Nu Ophiuchi has about three times the mass of the Sun and is roughly 330 million years old. The spectrum of the star matches a stellar classification of K0 IIIa, indicating it is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence of stars like the Sun. Unusually, it displays an anomalously low abundance of cyanogen for a star of its type.

PSR B1257+12, is a pulsar located 1000 light years from the Sun. In 1992, two planets were discovered orbiting the pulsar, and a third was confirmed in 1994.

PSR B1913+16 is a pulsar which together with another neutron star is in orbit around a common center of mass, thus forming a binary star system. PSR 1913+16 was the first binary pulsar to be discovered. In 1974 it was discovered by Russell Alan Hulse and Joseph Hooton Taylor, Jr., of the University of Massachusetts Amherst. Their discovery of the system and analysis of it earned them the 1993 Nobel Prize in Physics "for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation."
The system is also called the Hulse–Taylor binary pulsar after its discoverers.

Pi³ Orionis is the Bayer designation for a star in the equatorial constellation of Orion. It has the traditional name of Tabit and the Flamsteed designation 1 Orionis. At an apparent visual magnitude of 3.16, it is readily visible to the naked eye. Pi³ Orionis is the brightest star in the lion's hide that Orion is holding. The distance to this star, as measured using the parallax technique, is 26.32 light-years. Though no extrasolar planets have been observed around Pi³ Orionis, the star is considered a prime location for planets as small as the Earth.
Pi³ Orionis is a main-sequence star of spectral type F6 V. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Compared to the Sun, it has about 124% of the mass, 132% of the radius, and nearly 3 times the luminosity. This energy is being radiated from the star's outer atmosphere at an effective temperature of 6,516 K, giving it the yellow-white glow of an F-type star. Pi³ Orionis is most likely single; a nearby star is probably an optical companion.

The Pistol Star is a blue hypergiant and is one of the most luminous known stars in the Milky Way Galaxy. It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region. The star owes its name to the shape of the Pistol Nebula, which it illuminates. It is located approximately 25,000 light years from Earth in the direction of Sagittarius. It would be visible to the naked eye as a fourth magnitude star, if it were not for the interstellar dust that completely hides it from view in visible light.

Pleione is a binary star in the Pleiades star cluster, located roughly 390 light years away in the constellation of Taurus. Pleione was not given a Bayer designation, but did receive a Flamsteed number—hence its designation 28 Tauri. Since the star is located close to Atlas, it's difficult for stargazers to distinguish with the naked eye, even though it's a hot type B star 190 times more luminous than the Sun. Pleione rotates even faster than Achernar on its axis, close to its breakup velocity.
The brighter star of the binary pair, component A, is a classical Be star with certain distinguishing traits: periodic phase changes and a complex circumstellar environment composed of two gaseous disks at different angles to each other. Although some research on the system has been performed, stellar characteristics of the orbiting B component are not well known. Pleione is the seventh brightest star in the Pleiades, after Taygeta.

Polaris is the brightest star in the constellation, Ursa Minor, and the 45th brightest star in the night sky. It is very close to the north celestial pole, making it the current northern pole star.
It is a multiple star, comprising the main star, α UMi Aa, which is a supergiant; two smaller companions, α UMi B and α UMi Ab; and two distant components, α UMi C and α UMi D. α UMi B was discovered in 1780 by William Herschel.
Many recent papers calculate the distance to Polaris at about 434 light-years. Some suggest that it may be 30% closer, which, if correct, is especially notable because Polaris is the closest Cepheid variable to Earth, so its physical parameters are critically important to the whole astronomical distance scale.

Pollux is a star in the northern constellation of Gemini, the Twins. It is an evolved giant star with an orange hue. At an apparent visual magnitude of 1.1, Pollux is the brightest star in the constellation; brighter even than its neighbor Castor. Parallax measurements made with the Hipparcos astrometry satellite place it at a distance of about 33.78 light-years from Earth. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. In 2006, Pollux was confirmed to have an extrasolar planet orbiting it.

Proxima Centauri is a red dwarf about 4.24 light-years from the Sun, inside the G-cloud, in the constellation of Centaurus. It was discovered in 1915 by Scottish astronomer Robert Innes, the Director of the Union Observatory in South Africa, and is the nearest known star to the Sun, although it is too faint to be seen with the naked eye, with an apparent magnitude of 11.05. Its distance to the second- and third-nearest stars, which form the bright binary Alpha Centauri, is 0.237 ± 0.011 ly. Proxima Centauri is very likely part of a triple star system with Alpha Centauri A and B, but its orbital period may be greater than 500,000 years.
Because of the proximity of this star, its distance from the Sun and angular diameter can be measured directly, from which it can be determined that its diameter is about one-seventh of that of the Sun. Proxima Centauri's mass is about an eighth of the Sun's, and its average density is about 40 times that of the Sun. Although it has a very low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness because of magnetic activity.

RR Lyrae is a variable star in the Lyra constellation, located near the border with the neighboring constellation of Cygnus. As the brightest star in its class, it became the eponym for the RR Lyrae variable class of stars and it has been extensively studied by astronomers. RR Lyrae variables serve as important standard candles that are used to measure astronomical distances. The period of pulsation of an RR Lyrae variable depends on its mass, luminosity and temperature, while the difference between the measured luminosity and the actual luminosity allows its distance to be determined via the inverse square law. Hence, understanding the period-luminosity relation for a set of local RR Lyrae-type variable stars allows the distance of more distant stars of this type to be determined.
The variable nature of RR Lyrae was discovered by the Scottish astronomer Williamina Fleming at Harvard Observatory in 1901.
The distance of RR Lyrae remained uncertain until 2002 when the Hubble Space Telescope's Fine Guidance Sensor was used to determine the distance of RR Lyrae within a 5% margin of error, yielding a value of 854 light-years.

Rho Cassiopeiae is a yellow hypergiant star in the constellation Cassiopeia. It is about 8,200 light-years away from Earth, yet can still be seen by the naked eye, as it is 500,000 times more luminous than the Sun. On average, it has an absolute magnitude of −9.5, making it one of the visually brightest stars known. Its surface diameter measures 450 times that of the Sun, or approximately 630,000,000 kilometers. As a yellow hypergiant it is one of the rarest types of stars. Although only around a dozen are known in the Milky Way, it is not the only one in its constellation, which also includes V509 Cassiopeiae. Rho Cassiopeiae is a single star, and is categorized as a semiregular variable.

Rigel, also known by its Bayer designation Beta Orionis, is the brightest star in the constellation Orion and the seventh brightest star in the night sky, with visual magnitude 0.13. The star as seen from Earth is actually a triple star system, with the primary star a blue-white supergiant of absolute magnitude −7.84 and around 120,000 times as luminous as the Sun. An Alpha Cygni variable, it pulsates periodically. Visible in small telescopes, Rigel B is itself a spectroscopic binary system, consisting of two main sequence blue-white stars of spectral type B9.

SGR 1806-20 is a magnetar, a particular type of neutron star. It was discovered in 1979 and has been identified as a soft gamma repeater. SGR 1806-20 is located about 14.5 kiloparsecs from Earth on the far side of our Milky Way galaxy in the constellation of Sagittarius. It has a diameter of no more than 20 kilometres and rotates on its axis every 7.5 seconds. As of 2012, SGR 1806-20 is the most highly magnetized object ever observed, with a magnetic field over 10¹⁵ gauss in intensity. SGR 1806-20 has a magnetic field that is a quadrillion times stronger than that of the Earth.

Sagittarius A is a complex radio source at the center of the Milky Way. It is located in the Sagittarius constellation, and is hidden from view at optical wavelengths by large clouds of cosmic dust in the spiral arms of the Milky Way.
It consists of three components, the supernova remnant Sagittarius A East, the spiral structure Sagittarius A West, and a very bright compact radio source at the center of the spiral, Sagittarius A*. These three overlap: Sagittarius A East is the largest, West appears off-center within East, and A* is at the center of West.

Sigma Octantis is a magnitude 5.42 star in the constellation Octans most notable for being the current South Star. Sigma Octantis is approximately 270 light years from Earth, and is classified as a giant, with a spectral type of F0 III. It is a Delta Scuti variable, with magnitude varying by about 0.03 magnitudes over 2.3 hours.
Sigma Octantis is the dimmest star to be represented on a national flag. It appears on the flag of Brazil, symbolising the Brazilian Federal District.
Its position near the southern celestial pole makes it the southern hemisphere's pole star, hence its occasional name, Polaris Australis.

Sigma Sagittarii is the second brightest star in the constellation Sagittarius. Its modern name Nunki is an Assyrian or Babylonian name recovered by archaeologists and made public by R. H. Allen. Nunki has an apparent magnitude of +2.05, making it readily visible to the naked eye. The distance to this star, determined using parallax measurements from the Hipparcos astrometry satellite, yields an estimated value of 228 light-years from Earth.
Nunki has a spectrum matching a stellar classification of B2.5 V, which indicates this is a B-type main sequence star. The total luminosity of σ Sgr is 3300 times that of the Sun while it has a surface temperature of 18,890 K. X-ray emission has been detected from this star, which has an estimated X-ray luminosity of 1.2 × 10²⁸ erg s–1. Sigma Sgr has a magnitude +9.5 optical companion located 5.2 arcminutes away.
Because it is close to the ecliptic, Nunki can be occulted by the Moon and very rarely by planets. The last occultation of Nunki by a planet took place on November 17, 1981, when it was occulted by Venus. Furthermore, Nunki is the brightest star that can be principally occulted by an exterior planet between 5000 BC and 5000 AD.

Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Σείριος Seirios. The star has the Bayer designation Alpha Canis Majoris. What the naked eye perceives as a single star is actually a binary star system, consisting of a white main-sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, called Sirius B. The distance separating Sirius A from its companion varies between 8.2 and 31.5 AU.
Sirius appears bright because of both its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs, as determined by the Hipparcos astrometry satellite, the Sirius system is one of Earth's near neighbors. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to recede, but it will continue to be the brightest star in the Earth's sky for the next 210,000 years.
Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of 1.42.

The Sun is the star at the center of the Solar System. It is almost spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,684 km, around 109 times that of Earth, and its mass accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, whereas the rest is mostly helium. The remaining 1.69% consists of heavier elements, including oxygen, carbon, neon and iron, among others.
The Sun formed about 4.567 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, whereas the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all stars form by this process. The Sun is a G-type main-sequence star based on spectral class and it is informally designated as a yellow dwarf because its visible radiation is most intense in the yellow-green portion of the spectrum.

T Tauri is a variable star in the constellation Taurus, the prototype of the T Tauri stars. It was discovered in October 1852 by John Russell Hind. T Tauri appears from Earth amongst the Hyades cluster, not far from ε Tauri; but it is actually 420 light years behind it and was not formed with the rest of them.
Like all T Tauri stars, it is very young, being only a million years old. Its distance from Earth is about 460 light years, and its apparent magnitude varies unpredictably from about 9.3 to 14.
The T Tauri system consists of at least three stars, only one of which is visible at optical wavelengths; the other two shine in the infrared and one of them also emits radio waves. Through VLA radio observations, it was found that the young star dramatically changed its orbit after a close encounter with one of its companions and may have been ejected from the system.
Physically nearby is NGC 1555, a reflection nebula known as Hind's Nebula or Hind's Variable Nebula. It is illuminated by T Tauri, and thus also varies in brightness.

Tau Boötis is a yellow-white dwarf approximately 51 light-years away in the constellation of Boötes. The system is also a binary star system, with the secondary star being a red dwarf. As of 1999, an extrasolar planet has been confirmed to be orbiting the primary star.

Tau Ceti is a star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years from the Solar System, it is a relatively nearby star, and is the closest solitary G-class star. The star appears stable, with little stellar variation.
Tau Ceti is metal-deficient, a deficiency usually associated with systems having no giant planets and few terrestrial planets. Observations have however detected more than ten times as much dust surrounding Tau Ceti as is present in the Solar System.
Since December 2012, there has been evidence of possibly five planets orbiting Tau Ceti, with one of these being potentially in the habitable zone. Because of its debris disk, any planet orbiting Tau Ceti would face far more impact events than Earth. Despite this hurdle to habitability, its solar analog characteristics have led to widespread interest in the star. Given its stability, similarity and relative proximity to the Sun, Tau Ceti is consistently listed as a target for the Search for Extra-Terrestrial Intelligence, and it appears in some science fiction literature.

Theta Leonis is a star in the constellation Leo. It has the traditional names Chertan, Chort and Coxa. With an apparent visual magnitude of +3.324 it is visible to the naked eye and forms one of the brighter stars in the constellation. The distance from Earth can be directly determined from parallax measurements, yielding a value of about 165 light-years.
This is a large star with 2.5 times the mass of the Sun. The spectrum matches a stellar classification of A2 V, making this a seemingly typical A-type main sequence star. However, the spectrum shows enhanced absorption lines of metals, marking this as a chemically peculiar Am star. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, appears around 12% higher than in the Sun. It is radiating 141 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 9,350 K, literally giving it a white-hot glow.
Theta Leonis is much younger than the Sun, with an estimated age of around 550 million years. It has a moderately high rate of rotation, with a projected rotational velocity of 23 km s–1.

Thuban, also known by its Bayer designation Alpha Draconis, is a star in the constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star in ancient times. Thuban is an Arabic word for snake ثعبان thuʿbān.
Even though Johann Bayer gave Thuban the designation Alpha, its apparent magnitude of 3.65 is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis, whose apparent magnitude is 2.24.

V838 Monocerotis is a red variable star in the constellation Monoceros about 20,000 light years from the Sun. The previously unknown star was observed in early 2002 experiencing a major outburst, and was possibly one of the largest known stars for a short period following the outburst. Originally believed to be a typical nova eruption, it was then realized to be something completely different. The reason for the outburst is still uncertain, but several conjectures have been put forward, including an eruption related to stellar death processes and a merger of a binary star or planets.
The remnant is evolving rapidly. By 2009 its temperature had increased to 3,270K and its luminosity was 15,000 times solar, but its radius had decreased to 380 times that of the sun although the ejecta continues to expand. The opaque ejected dust cloud has completely engulfed the B-type companion.

VB 10 or Van Biesbroeck's star is a very small and very dim M-type red dwarf located in the constellation Aquila. It is part of a binary star system. Although it is relatively close to Earth, at about 19 light years, VB 10 is a dim magnitude 17, making it difficult to image with amateur telescopes as it can get lost in the glare of the primary star.

VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus, approximately 5,000 light years from Earth. A red supergiant fills the system's Roche lobe when closest to its companion blue star, the latter appearing to be on the main sequence. Matter flows from the red supergiant onto the blue companion for at least part of the orbit and the hot star is obscured by a large disk of material. The red supergiant primary, known as VV Cephei A, is currently recognised as one of the largest stars in the galaxy, with an estimated solar radius of 1,475. It should be possible to calculate the masses of eclipsing binary stars with some accuracy, but in this case mass loss, changes in the orbital parameters, a disk obscuring the hot secondary, and doubt about the distance of the system have led to wildly varying estimates. Calculations before the most recent primary and secondary eclipses had started to settle on masses of around 20 for both stars, but more recent papers have suggested that even this is too high.

Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus. It is a relatively close star at only 25 light-years from Earth, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood.
Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun." Vega was the northern pole star around 12,000 BCE and will be so again around the year 13,727 when the declination will be +86°14'. Vega was the first star other than the Sun to be photographed and the first to have its spectrum recorded. It was one of the first stars whose distance was estimated through parallax measurements. Vega has served as the baseline for calibrating the photometric brightness scale, and was one of the stars used to define the mean values for the UBV photometric system.

Winnecke 4 is a double star in the constellation Ursa Major. It was discovered by Charles Messier in 1764 while he was searching for a nebula that had been reported in the area by Johann Hevelius. Not seeing any nebulae, Messier catalogued this double star instead. It was subsequently rediscovered by Friedrich August Theodor Winnecke in 1863, and included in the Winnecke Catalogue of Double Stars as number 4. Burnham calls M40 "one of the few real mistakes in the Messier catalog," faulting Messier for including it when all he saw was a double star, not a nebula of any sort.
In 1991 the separation between the components was measured at 51".7, an increase since Messier's time. Data gathered by astronomers Brian Skiff and Richard L. Nugent strongly suggest that this is merely an optical double star rather than a physically connected system.
The nearby nebula observed by Hevelius may have been the nearby ring galaxy NGC 4290. The galaxy, being 12th magnitude, may have been bright enough to notice for large telescopes at the time, but not quite bright enough for Messier.

Wolf 359 is a red dwarf that is located in the constellation Leo, near the ecliptic. At a distance of approximately 7.8 light years from the Earth, it has an apparent magnitude of 13.5 and can only be seen with a large telescope. Wolf 359 is one of the nearest stars to the Solar System; only the Alpha Centauri system, Barnard's Star, Luhman 16, and WISE 0855–0714 are known to be closer. Its proximity to Earth has led to its mention in several works of fiction.
Wolf 359 is one of the faintest and lowest-mass stars known. At the light-emitting layer called the photosphere, it has a temperature of about 2,800 K, which is low enough for chemical compounds to form and survive. The absorption lines of compounds such as water and titanium oxide have been observed in the spectrum. The surface has a magnetic field that is stronger than the average magnetic field on the Sun. As a result of magnetic activity caused by convection, Wolf 359 is a flare star that can undergo sudden increases in luminosity for several minutes. These flares emit strong bursts of X-ray and gamma ray radiation that have been observed by space telescopes.

Xi Persei is a star in the constellation Perseus. It has the traditional name Menkib . Menkib has an apparent magnitude of +4.06 and is classified as a blue giant (spectral class O7.5III). It is approximately 1800 light years from Earth.
It is intrinsically 12,700 times brighter than the Sun with absolute magnitude -5.5 in the V band. If the ultraviolet light that emanates from Menkib is included in its total, bolometric, luminosity is 263,000 times that of the Sun.
The star has a mass of some 30 solar masses and a surface temperature of 35,000 kelvins, making it one of the hottest stars that can be seen with the naked eye. The fluorescence of the California Nebula (NGC 1499) is due to this star’s prodigious radiation.

Zeta Leonis is a third-magnitude star in the constellation Leo, the lion. It has the traditional name Adhafera, from the Arabic الضفيرة al-ðafīrah "the braid/curl", a reference to its position in the lion's mane. It forms the second star in the blade of "The Sickle", which is an asterism formed from the head of Leo.

Zeta Ophiuchi is a star located in the constellation of Ophiuchus. It has an apparent visual magnitude of 2.57, making it the third brightest star in the constellation. Parallax measurements give an estimated distance of roughly 366 light-years from the Earth.

Zeta Puppis is a star in the constellation of Puppis. It is also known by the traditional names Naos and Suhail Hadar in Arabic.
Its spectral class is O4If, making it an exceptionally hot star, and it is one of the sky's few naked-eye class O-type stars as well as one of the closest to Earth. It had been assumed to be part of the Vela complex near the Gum nebula over 400 parsecs from Earth, but the 2008 reduction of Hipparcos data gave a distance of 335 parsecs ± 4%. Its surface temperature is 42,000 K . The current mass is calculated at 22.5 solar masses and the radius at 14 times the solar radius but these values are highly uncertain. Older derivations assumed the larger distance and were correspondingly larger, but some new calculations still give values up to twice these.
Zeta Puppis is an extreme blue supergiant, one of the most luminous stars in the Milky Way. Visually, it is 12,500 times more powerful than the Sun, but being an extreme blue star, most of its radiation is in the ultraviolet and hence its bolometric luminosity is over 500,000 times that of the sun. It is also the 62nd brightest star in terms of apparent magnitude from Earth

16 Cygni or 16 Cyg is a triple star system approximately 69 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 1996 an extrasolar planet was discovered in an eccentric orbit around 16 Cygni B.

40 Eridani is a triple star system less than 16.5 light years away from Earth, in the constellation Eridanus. It is also known as Omicron² Eridani for all components, or Keid for component A, from the Arabic word qayd, shells.
The primary star of the system, 40 Eridani A, is easily visible to the naked eye. The pair 40 Eridani B/C was discovered on January 31, 1783, by William Herschel, p. 73 It was again observed by Friedrich Georg Wilhelm Struve in 1825 and by Otto Wilhelm von Struve in 1851. In 1910, it was discovered that although component B was a faint star, it was white in color. This meant that it had to be a small star; in fact it was a white dwarf, the first discovered.

61 Cygni, sometimes called Bessel's Star or Piazzi's Flying Star, is a visual binary system in the constellation Cygnus. It consists of a pair of K-type dwarf stars that orbit each other in a period of about 659 years, forming a visual binary. At fifth and sixth apparent magnitudes, they are among the least conspicuous stars visible in the night sky to an observer without an optical instrument.
61 Cygni first attracted the attention of astronomers because of its large proper motion. In 1838, Friedrich Wilhelm Bessel measured its distance from Earth at about 10.3 light years, very close to the actual value of about 11.4 light years; this was the first distance estimate for any star other than the Sun, and first star to have its stellar parallax measured. Over the course of the twentieth century, several different astronomers reported detections of a massive planet orbiting one of the two stars, but recent high-precision radial velocity observations have shown that all such claims were erroneous. To date, no planets have been confirmed in this system and all of the past claims are now considered spurious.

AE Aquarii is a cataclysmic variable binary star of the DQ Herculis type. Based upon parallax measurements, the system is located at a distance of about 280 light-years from the Earth. Because of its unique properties, this system has been subject to a number of scientific studies.
The AE Aquarii system consisting of an ordinary star in a close orbit around a magnetic white dwarf; the pair orbit each other with a period of 9.88 hours. The white dwarf primary has 63% of the Sun's mass but a radius of only about 1% of the Sun. As of 2009, it has the shortest known spin period of any white dwarf, completing a full revolution every 33.08 seconds. This spin is decreasing at a rate of 1.78 ns per year, which is unusually high. The secondary star has a stellar classification of K4-5 V, making it a main sequence star that is generating energy at its core through the thermonuclear fusion of hydrogen. It has about 37% of the Sun's mass but 79% of the Sun's radius.
This system displays flare activity that has been observed across multiple bands of the electromagnetic spectrum, including X-rays.

Alcyone is a star system in the constellation Taurus. It is the brightest star in the Pleiades open cluster, which is a young cluster, aged at less than 50 million years. Alcyone is approximately 400 light years from Earth. It is named after the mythological figure Alcyone, one of the mythological Pleiades. It is known as 昴宿六 in Chinese.

Alpha Cancri is a star system in the constellation Cancer. It has the traditional name Acubens, from the Arabic الزوبنةal zubanāh, "the claws"

Alpha Herculis is a multiple star system in the constellation Hercules. It has the traditional name Rasalgethi or Ras Algethi, and the Flamsteed designation 64 Herculis. The traditional name "Head" comes from the fact that in antiquity Hercules was depicted upside down on the constellation maps.
The term ra's al-jaθiyy or Ras al Djathi was appeared in the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, which was translated into Latin as Caput Ingeniculi.
In Chinese astronomy, Rasalgethi is called 帝座, Pinyin: Dìzuò, meaning Emperor's Seat, this star is marking itself and stand alone in the center of Emperor's Seat asterism, Heavenly Market enclosure. 帝座 was westernized into Ti Tso by R.H. Allen, with the same meaning

Alpha Librae is the Bayer designation for the second brightest star in the constellation Libra. It has the traditional name Zubenelgenubi. The name, from Arabic الزبن الجنوبي, means "southern claw" and was coined before Libra was recognized as distinct from Scorpius. The alternate names Kiffa Australis and Elkhiffa Australis, partial Latin translations of Arabic al-kiffah al-janūbiyy, mean "southern pan". Another name used in older astronomy texts, equivalent to "southern scale or pan", was Lanx Australis.
Alpha² Librae is 0.33 degree from the ecliptic so it can be easily occulted by the Moon and by planets. The next occultation by a planet will be by Mercury on 10 November 2052.

Atlas is a triple star system in the Pleiades open cluster. It is also known as 27 Tauri.
The primary component, Atlas A, is a blue-white B-type giant with an apparent magnitude of +3.62. It is a spectroscopic binary whose components have magnitudes of +4.1 and +5.6. The binary makes one orbit every 1250 days. Atlas also has a dimmer magnitude +6.8 companion, Atlas B, at a separation of 0.4 arcseconds or at least 52 astronomical units away.

BD Camelopardalis is an S star and symbiotic star in the constellation Camelopardalis. It was recognized as a spectroscopic binary star in 1922, and its orbital solution published in 1984; it has a 596-day orbital period. A spectroscopic composition analysis was done of the red giant primary star in 1986.

Beta Arietis is a binary star system in the constellation Aries, marking the Ram's second horn. It has the traditional name Sherawan, and the Flamsteed designation 6 Arietis. The traditional name, in full Al Sharatan, is from the Arabic الشراطان aš-šarāţān "the two signs", a reference to the star having marked the northern vernal equinox together with Gamma Arietis several thousand years ago.
In Chinese, 婁宿, meaning Bond, refers to an asterism consisting of β Arietis, γ Arietis and α Arietis. Consequently, β Arietis itself is known as 婁宿一.

Beta Lyrae is a binary star system approximately 960 light-years away in the constellation Lyra. Beta Lyrae has the traditional name Sheliak, from الشلياق šiliyāq, the Arabic name of the constellation Lyra. The Bayer designation for this star was given by the German astronomer Johann Bayer with the publication of his star atlas Uranometria in 1603. It was given the Flamsteed designation 10 Lyrae by John Flamsteed in 1712 with the first publication of his star catalogue. The variable luminosity of this system was discovered in 1784 by the British amateur astronomer John Goodricke.
Beta Lyrae is a semidetached binary system made up of a stellar class B7II primary star and a secondary that is probably also a B-type star. The fainter, less massive star in the system was once the more massive member of the pair, which caused it to evolve away from the main sequence first and become a giant star. Because the pair are in a close orbit, as this star expanded into a giant it filled its Roche lobe and transferred most of its mass over to its companion.

Beta Scorpii is a multiple star system in the southern zodiac constellation of Scorpius. It has the traditional names Acrab, Akrab or Elacrab, all come from al-'Aqrab, the Scorpion, for the whole constellation, as well as Graffias, a name it shares with Xi Scorpii. It was known as 房宿四 in Chinese.
Observed through a small telescope, Beta Scorpii appears as a binary star with a separation between the two components of 13.5 arcseconds. This pair, β¹ and β², form the top branches of the hierarchy of orbiting components in this system. β¹ Scorpii, the brighter of the pair, consists of two sub-components, β Sco A and β Sco B, orbiting at an angular separation of 3.9 arcseconds with an orbital period of 610 years. β Sco A is itself a spectroscopic binary with the components β Sco Aa and β Sco Ab separated by 1.42 milliarcseconds and an orbital period of 6.82 days.
The second visual component, β² Scorpii, has two sub-components, β Sco C and β Sco E, orbiting at an angular separation of 0.1328 arcseconds with an orbital period of 39 years. β Sco E is a spectroscopic binary with the components β Sco Ea and β Sco Eb having an orbital period of 10.7 days.

Cor Caroli is the brightest star in the northern constellation Canes Venatici. It is a binary star consisting of two distantly separated components. The name Cor Caroli means "Charles's Heart", and was named in the 17th century to honour the King Charles I of England who was beheaded in 1649.

Delta Capricorni, also traditionally named Deneb Algedi and Scheddi, is a binary star system approximately 39 light-years away in the constellation of Capricornus. The primary star in the system is a white giant star and the combined light of its members makes it the brightest "single" star within the constellation.
Because it is near the ecliptic, Delta Capricorni can be occulted by the Moon, and also by planets.

Delta Cephei is the Bayer designation for a binary star system located approximately 887 light-years away in the northern circumpolar constellation of Cepheus, the King. At this distance, the visual magnitude of the star is diminished by 0.23 as a result of extinction caused by gas and dust along the line of sight. It is the prototype of the Cepheid variable stars that undergo periodic changes in luminosity.

Delta Muscae, often catalogued as HD 112985, is a spectroscopic binary star system and the closest to the Earth in the southern hemisphere constellation of Musca at a distance of approximately 27.8 parsecs. The main star is classified as a giant star with an orange tint. It is one of the stars given a Bayer designation by astronomer Johann Bayer. It was recorded in Bayer's 1603 publication Uranometria. In addition it is one of the main stars used in the visual formation of the Musca constellation.

Delta Scorpii is a star in the constellation Scorpius. It has the traditional name Dschubba or Dzuba, from Arabic jabhat, "forehead"; also Iclarcrau or Iclarkrav.
Because Delta Scorpii is near the ecliptic it is occasionally occulted by the Moon, or by planets.
Delta Scorpii is a proper motion member of the Upper Scorpius subgroup of the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years. A recent analysis of the HR diagram position for Delta Scorpii estimates its effective temperature to be 27,400 K with a luminosity of 38,000 times that of the Sun, consistent with an isochronal age of 9–10 million years and an estimated mass of 14.6–14.9 solar masses.

Epsilon Boötis is a double star in the northern constellation of Boötes. It has the traditional names Izar and Pulcherrima. The star system can be viewed with the unaided eye at night, but resolving the pair with a small telescope is challenging; an aperture of 76 mm or greater is required.

Epsilon Lyrae, also known as the Double Double, is a multiple star system approximately 162 light-years away in the constellation of Lyra.

Eta Carinae is a stellar system in the constellation Carina, about 7,500 to 8,000 light-years from the Sun. The system contains at least two stars, of which the primary is a luminous blue variable that initially had around 150 solar masses, of which it has lost at least 30. A hot supergiant of approximately 30 solar masses is in orbit around the primary, although an enormous thick red nebula surrounding Eta Carinae makes it impossible to detect this companion at optical wavelengths. The Eta Carinae system is enclosed in the Homunculus Nebula, in turn a part of the much larger Carina Nebula, and currently has a combined bolometric luminosity of over five million times the Sun's. It is not visible north of latitude 30°N and is circumpolar south of latitude 30°S. Because of its mass and the stage of its life, it is expected to explode as a supernova or hypernova in the astronomically near future.

Eta Cassiopeiae is a star system in the northern circumpolar constellation of Cassiopeia. It has the traditional name Achird. Based upon parallax measurements, the distance to this system is 19.42 light-years from Earth.
In Chinese, 王良, meaning Wang Liang, refers to an asterism consisting of η Cassiopeiae, β Cassiopeiae, κ Cassiopeiae, α Cassiopeiae and λ Cassiopeiae. Consequently, η Cassiopeiae itself is known as 王良三

GRS 1915+105 or V1487 Aquilae is an X-ray binary star system which features a regular star and a black hole. It was discovered on August 15, 1992 by the WATCH all-sky monitor aboard Granat. "GRS" stands for "GRANAT source", "1915" is the right ascension and "105" is declination in units of 0.1 degree. The NIR counterpart was confirmed by spectroscopic observations. The binary system lies 11,000 parsecs away in Aquila. GRS 1915+105 is the heaviest of the stellar black holes so far known in the Milky Way Galaxy, with 10 to 18 times the mass of the Sun. It is also a microquasar, and it appears that the black hole may rotate at 1,150 times per second.

Gamma Andromedae is the third brightest point of light in the constellation of Andromeda. It is also known by the traditional name Almach.
In 1778, Johann Tobias Mayer discovered that γ Andromedae was a double star. When examined in a small telescope, it appears to be a bright, golden yellow star next to a dimmer, indigo blue star, separated by approximately 10 arcseconds. It is often considered by stargazers to be a beautiful double star with a striking contrast of color. It was later discovered that γ² Andromedae is itself a triple star system. What appears as a single star to the naked eye is thus a quadruple star system, approximately 350 light-years from the Earth.

Gamma Cephei, traditionally named Errai, Er Rai, and or Alrai, is a binary star system approximately 45 light-years away in the constellation of Cepheus. Gamma Cephei contains an apparent magnitude of 3.22. The visible part of the system is a stellar class K1III-IV orange subgiant star on its first ascent off the main sequence. It is about 6.6 billion years old. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
Gamma Cephei is the naked-eye star that will succeed Polaris as the Earth's northern pole star, due to the precession of the equinoxes. It will be closer to the northern celestial pole than Polaris around 3000 CE and will make its closest approach around 4000 CE. The "title" will pass to ι Cephei some time around 5200 CE.
The star has a companion star with a mass approximately 0.409 times that of our Sun. Gamma Cephei B is of stellar mass and is assumed to be of similar age to its primary. It is probably a red dwarf of class M4, 6.2 degrees of magnitude fainter than the K-type primary star.

Gliese 229 is a red dwarf about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun, 69% of the Sun's radius, and a very low projected rotation velocity of 1 km/s at the stellar equator.
The star is known to be a low activity flare star, which means it undergoes random increases in luminosity because of magnetic activity at the surface. The spectrum shows emission lines of calcium in the H and K bands. The emission of X-rays has been detected from the corona of this star. These may be caused by magnetic loops interacting with the gas of the star's outer atmosphere. No large-scale star spot activity has been detected.
The space velocity components of this star are U = +12, V = –11 and W = –12 km/s. The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.

The Great Diamond is an asterism. Astronomy popularizer Hans A. Rey called it the Virgin's Diamond. It is composed of the stars Cor Caroli, Denebola, Spica, and Arcturus. It is somewhat larger than the Big Dipper.
The three southernmost stars are sometimes given their own asterism, the Spring Triangle.
Lying within the Great Diamond is the set of stars traditionally assigned to Coma Berenices. Many nearby galaxies, including galaxies within the Virgo Cluster, are located within this asterism, and some of these galaxies can easily be observed with amateur telescopes.

HD 189733, also catalogued as V452 Vulpeculae, is a binary star system approximately 63 light-years away in the constellation of Vulpecula. The primary star is suspected to be an orange dwarf star, while the secondary star is a red dwarf star. Given that this system has the same visual magnitude as HD 209458, it promises much for the study of close transiting extrasolar planets. The star can be found with binoculars 0.3 degrees east of the Dumbbell Nebula.
As of 2005, it has been confirmed that an extrasolar planet orbits the primary star within the system.

HD 80606 and HD 80607 are two stars comprising a binary star system approximately 190 light-years away in the constellation of Ursa Major. Both stars orbit each other at an average distance of 1,200 astronomical units. The binary system is listed as Σ1341 in the Struve Catalogue of Double Stars, however this designation is not in wide use and the system is usually referred to by the HD designations of its constituent stars. An extrasolar planet has been confirmed to orbit HD 80606 in a highly elliptical orbit.

Lambda Scorpii is a blue star and the second brightest star system in the constellation Scorpius, and one of the brightest stars in the nighttime sky. It has the Bayer designation λ despite being the second brightest in its constellation. It has the traditional name Shaula, which comes from the Arabic الشولاء al-šawlā´ meaning the raised [tail], as it is found in the tail of the scorpion. It is known as Wei Xiu Ba 尾宿八 in Chinese.

Luyten 726-8 is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus. Luyten 726-8B is also known under the variable star designation UV Ceti, being the archetype for the class of flare stars.
The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and cataloged it as Luyten 726-8. The two stars are of nearly equal brightness, with visual magnitudes of 12.7 and 13.2 as seen from Earth. They orbit one another every 26.5 years. The distance between the two stars varies from 2.1 to 8.8 astronomical units (310 to 1,320 Gm). The Luyten 726-8 system is approximately 2.63 parsecs (8.58 ly) from Earth's Solar System, in the constellation Cetus, and is thus the seventh-closest star system to Earth. Its own nearest neighbor is Tau Ceti, 0.88 pc (2.87 ly) away from it. If R_v=+29 km/s then approximately 28,700 years ago Luyten 726-8 was at its minimal distance of 2.21 pc (7.2 ly) from the Sun.

Mintaka is a star some 916 light years distant in the constellation Orion. It has a Bayer designation of Delta Orionis and a Flamsteed designation of 34 Orionis. The name Mintaka comes from منطقة manṭaqa, which means "the belt" in Arabic. Together with Alnitak and Alnilam, the three stars make up the belt of Orion, known by many names among ancient cultures. When Orion is close to the meridian, Mintaka is the right-most of the belt's stars as seen by an observer in the Northern Hemisphere facing south.

Mira is a red giant star estimated 200–400 light years away in the constellation Cetus. Mira is a binary star, consisting of the red giant Mira A along with Mira B. Mira A is also an oscillating variable star and was the first non-supernova variable star discovered, with the possible exception of Algol. Mira is the brightest periodic variable in the sky that is not visible to the naked eye for part of its cycle. Its distance is uncertain; pre-Hipparcos estimates centered on 220 light-years; while Hipparcos data from the 2007 reduction suggest a distance of 299 light-years, with a margin of error of 11%.

Mu Boötis is a triple star system in the constellation Boötes. It has the traditional name Alkalurops, and the Flamsteed designation 51 Boötis. Mu Boötis is approximately 121 light-years from Earth.
The name Alkalurops is from Greek καλαύροψ kalaurops "shepherd's staff", through the Arabic.
It is known as 七公六 in Chinese.
The primary component, μ¹ Boötis, is a yellow-white F-type subgiant with an apparent magnitude of +4.31.

S Antliae is a W Ursae Majoris-type eclipsing binary variable star in Antlia. It varies in apparent magnitude from 6.27 to 6.83 over a period of 15.6 hours. The system shines with a combined spectrum of A9V. Based upon an annual parallax shift of 11.84 milliarc seconds as measured by the Hipparcos satellite, this system is 270 light-years from Earth. Analysing and recalibrating yields a parallax of 13.30 and hence a distance of 250 light-years. The system is classed as an A-type W Ursae Majoris variable—the primary is hotter than the secondary and the drop in magnitude is caused by the latter passing in front of the former. Calculating the properties of the component stars from the orbital period indicates that the primary star has a mass 1.94 times and a diameter 2.026 times that of the Sun, and the secondary has a mass 0.76 times and a diameter 1.322 times that of the Sun. The primary has a surface temperature of 7800 K, while the secondary is a little cooler at 7340 K. The two stars have similar luminosity and spectral type as they have a common envelope and share stellar material. The system is thought to be around 5-6 billion years old.

SS 433 is one of the most exotic star systems observed. It is an eclipsing X-ray binary system, with the primary most likely a black hole, or possibly a neutron star. The spectrum of the secondary companion star suggests that it is a late A-type star. SS 433 is a microquasar, the first discovered.
SS 433's designation comes from its catalogers, Case Western Reserve astronomers Nicholas Sanduleak and C. Bruce Stephenson. It was the 433rd entry in their 1977 catalog of stars with strong emission lines.

The Solar System comprises the Sun and the objects that orbit it, whether they orbit it directly or by orbiting other objects that orbit it directly. Of those objects that orbit the Sun directly, the largest eight are the planets that form the planetary system around it, while the remainder are significantly smaller objects, such as dwarf planets and small Solar System bodies such as comets and asteroids.
The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. The vast majority of the system's mass is in the Sun, with most of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, called the gas giants, are substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are composed largely of substances with relatively high melting points, called ices, such as water, ammonia and methane, and are often referred to separately as "ice giants".

Theta Eridani is a star in the constellation Eridanus. It has the traditional name Acamar from the Arabic آخِر النَّهْر Ākhir an-nahr which means "the end of the river". Historically, Acamar represented the end of the constellation Eridanus. Now that distinction is held by the star Achernar, a star which shares the same Arabic etymology. Achernar is not visible from the Greek isles, hence the choice of Acamar as the river's end during the time of Hipparchus and later Ptolemy.
The term Ākhir an-nahr or Achr al Nahr was appeared in the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, which was translated into Latin as Postrema Fluminis.
In Chinese, 天園, meaning Celestial Orchard, refers to an asterism consisting of θ Eridani, χ Eridani, φ Eridani, κ Eridani, HD 16754, HD 23319, HD 24072, HD 24160, υ⁴ Eridani, 43 Eridani, υ² Eridani and υ¹ Eridani. Consequently, θ Eridani itself is known as 天園六
Acamar is a double star with some evidence suggesting it is part of a multiple star system. The main star, θ¹ Eri, is of the spectral class A4 and has a +3.2 apparent magnitude. Its companion star, θ² Eri, is of the spectral class A1 and has an apparent magnitude of +4.3.

UScoCTIO 108 is a binary system, approximately 470 light-years away in the Upper Scorpius OB association. The primary, UScoCTIO 108A, with mass around 0.06 solar masses, is a brown dwarf or low-mass red dwarf. The secondary, UScoCTIO 108B, with a mass around the deuterium burning limit of 13 Jupiter masses, would be classified as either a brown dwarf or an extrasolar planet.

UX Tauri, abbreviated as UX Tau, is a binary star system approximately 450 light-years away in the constellation of Taurus. It is notable for the fact that, despite its recent creation, the Spitzer Space Telescope discovered that its protoplanetary disk contains a gap. The dust, which normally accumulates in an expanding ring starting right next to the star at such a young age, is either very thin or nonexistent at a range of 0.2 to 56 AU from the star. Typically, this means that the early ancestors of planets may be forming from the disk, though the star only ignited about 1 million years ago. In contrast, Earth was formed approximately 4.54 billion years ago, placing its formation about sixty million years after the Sun's ignition around 4.6 billion years ago.