What is a constellation?
A constellation is a group of stars that, when seen from Earth, form a pattern. The stars in the sky are divided into 88 constellations.
The brightest constellation is Crux (the Southern Cross). The constellation with the greatest number of visible stars in it is Centaurus (the Centaur – with 101 stars). The largest constellation is Hydra (the Water Snake) which extends over 3.158% of the sky.
There are also asterisms, smaller apparent star patterns within a constellation, like the Big Dipper (in Ursa Major), the Little Dipper (in Ursa Minor), Keystone (in Hercules), and the Pleiades (in Taurus).
The 88 constellations
The 12 constellations of the Zodiac
The zodiac is a band of 12 constellations along the ecliptic.
|Aquarius, the water bearer||Libra, the scales|
|Aries, the ram||Pisces, the fish|
|Cancer, the crab||Sagittarius, the archer|
|Capricorn, the goat||Scorpius, the scorpion|
|Gemini, the twins||Taurus, the bull|
|Leo, the lion||Virgo, the virgin|
The constellations of the Southern Hemisphere
(some are seasonally visible in the Northern Hemisphere)
|Apus, the bird of paradise||Mensa, the table|
|Ara, the altar||Musca, the fly|
|Carina, the ship’s keel||Norma, the surveyor’s level|
|Centaurus, the centaur||Octans, the octant|
|Chamaeleon, the chameleon||Pavo, the peacock|
|Circinus, the compass||Phoenix, the phoenix|
|Crux, the southern cross||Pictor, the easel|
|Dorado, the swordfish||Reticulum, the net|
|Eridanus, the river||Triangulum Australe, the southern triangle|
|Grus, the crane||Tucana, the toucan|
|Hydrus, the water snake||Vela, the ship’s sails|
|Indus, the Indian||Volans, the flying fish|
|Lepus, the rabbit|
The constellations of the Northern Hemisphere
(some are seasonally visible in the Southern Hemisphere)
|Andromeda, the princess||Hydra, the water snake|
|Antlia, the pump||Lacerta, the lizard|
|Aquila, the eagle||Leo Minor, the little lion|
|Auriga, the chariot driver||Lupus, the wolf|
|Bootes, the herdsman||Lynx, the lynx|
|Caelum, the chisel||Lyra, the harp|
|Camelopardalis, the giraffe||Microscopium, the microscope|
|Canes Venatici, the hunting dogs||Monoceros, the unicorn|
|Canis Major, the big dog||Ophiuchus, the sepent holder|
|Canis Minor, the little dog||Orion, the hunter|
|Cassiopeia, the queen||Pegasus, the flying horse|
|Cepheus, the king||Perseus, the Medusa killer|
|Cetus, the whale||Pisces Austrinus, the southern fish|
|Columba, the dove||Puppis, the ship’s stern|
|Coma Berenices, Berenice’s hair||Pyxis, the ship’s compass|
|Corona Australis, the southern crown||Sagitta, the arrow|
|Corona Borealis, the northern crown||Sculptor, the sculptor|
|Corvus, the crow||Scutum, the shield|
|Crater, the cup||Serpens, the snake|
|Cygnus, the swan||Sextans, the sextant|
|Delphinus, the dolphin||Telescopium, the telescope|
|Draco, the dragon||Triangulum, the triangle|
|Equuleus, the little horse||Ursa Major, the big bear|
|Fornax, the furnace||Ursa Minor, the little bear|
|Hercules, the hero||Vulpecula, the little fox|
|Horologium, the clock|
There are many families of constellations. These families consist of constellations that either are close to one another in our view of the sky or have some other relationship (for example, depicting figures from a particular ancient myth). Some constellation families include:
- The Zodiac
- 12 constellations are star groupings that lie along the ecliptic (the plane in which most of our Solar System lies). Usually, 12 constellations are listed in the Zodiac, but there is actually a thirteenth constellation that crosses the ecliptic, Ophiuchus (between Scorpio and Sagittarius). The signs of the Zodiac are Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius.
- The Ursa Major Family
- 10 constellations circling the northern celestial pole, including Ursa Major (containing the Big Dipper), Ursa Minor (containing Polaris, the northern pole star), Canes Venatici, Boötes, Coma Berenice, Corona Borealis, Camelopardalis, Lynx, Draco, and Leo Minor.
- The Perseus Family
- 9 constellations depicting figures from the myth of Perseus, including Cassiopeia, Cepheus, Andromeda, Perseus, Pegasus, Cetus, Auriga, Lacerta, Triangulum.
- The Hercules Family
- 19 constellations depicting figures from the myth of Heracles, including Hercules, Sagitta, Aquila, Lyra, Cygnus, Vulpecula, Hydra, Sextans, Crater, Corvus, Ophiuchus, Serpens, Scutum, Centaurus, Lupus, Corona Australis, Ara, Triangulum Australe, Crux.
- The Orion Family
- 5 constellations, including Orion (the hunter), Canis Major and Canis Minor (Orion’s two gods), Monoceros (the unicorn), Lepus (the hare).
- The Heavenly Waters (aka the Cosmic Waters)
- 9 constellations whose names are related to water, including Delphinus, Columba, Equuleus, Vela, Puppis, Eridanus, Piscis Austrinus, Carina, Pyxis,
- The Bayer Group
- 11 Southern Hemisphere constellations depicting animals, named by Johann Bayer in 1603. Includes Hydrus, Dorado, Volans, Apus, Pavo, Grus, Phoenix, Tucana, Indus, Chamaeleon, Musca.
- The La Caille Family
- 13 Southern Hemisphere constellations, named by Nicolas Louis de Lacaille in 1756. Includes Norma, Fornax, Circinus, Telescopium, Microscopium, Sculptor, Caelum, Horologium, Antlia, Pictor, Reticulum, Octans, Mensa.
- [Abbreviation: And] Andromeda (the princess, the daughter of Cassiopeia) is a northern hemisphere constellation. Alpha Andromeda (called Sirrah, meaning “Horse’s navel”) is the same as Delta Pegasi (from the constellation Pegasus).
- [Abbreviation: Aqr] Aquarius (the water bearer) is a constellation of the zodiac. This faint constellation is seen along the ecliptic. The sun passes through Aquarius from mid-February until mid-March. There are many interesting celestial objects in this large constellation, including globular clusters (M2 and M72), planetary nebulae (NGC 7009 and NGC 7293), the star group M73, a double star (zeta Aqr). Aquarius is the radiant for the meteor showers: March Aquarids, Delta Aquarids, Eta Aquarids, and Iota Aquarids. Alpha Aquarii (the brightest star in Aquarius) is called Sadalmelik (meaning the Lucky One of the King) and beta Aquarii (the second-brightest star in Aquarius) is named Sadalsuud (meaning the Luckiest of the Lucky); they are twin supergiants.
- [Abbreviation: Ari] Aries (the ram) is a constellation of the zodiac located along the ecliptic between Pisces and Taurus. This tiny, faint constellation is seen just north of the ecliptic. The brightest star in Aries (Alpha Ari) is Hamal, the second-brightest star (Beta Ari) is Sharatan, the third-brightest star (Gamma 2 Ari) is Mesarthim, and the fourth-brightest is Botein (Delta Ari)
- Big Dipper
- The Big Dipper is a group of 7 stars (it is an asterism and not a constellation) contained in the Northern Hemisphere constellation Ursa major (The Great Bear).
- [Abbreviation: Boo] Boötes (the herdsman) is a large constellation in the northern hemisphere. The brightest star in Boötes is Arcturus, a red giant that is the fourth brightest star in the sky.
- [Abbreviation: Cnc] Cancer (the crab) is a very faint constellation of the zodiac that is shaped like a crab. Cancer is seen along the ecliptic and is located between Leo and Gemini. At the center of the crab’s shell is a huge open cluster, the Beehive cluster, also known as Praesepe (M44). The open cluster M67 is nearby. The brightest star in Cancer is Acubens (meaning claw); the second-brightest is Al Tarf (meaning tip).
- Canis Major
- Canis major (The Great Dog) is a constellation near Orion. The brightest star in Canis Major (and the brightest star in the sky) is Sirius, also known as the dog star. Canis Major is one of the constellation Orion’s hunting dogs (together with Canis Minor).
- Canis Venatici
- Canes Venatici (The Two Hunting Dogs or greyhounds [of the herdman Boötes]) is a small Northern Hemisphere constellation near Ursa Major and Boötes. The brightest star in Canis Venatici is Cor Caroli (alpha CVn), a blue-white star (magnitude 2.9) with a companion star (magnitude 5). The Whirlpool Nebula (M51), the Sab galaxy (M94) and the globular cluster M3 (magnitude 6) can be found in Canis Venatici. The Canes Venaticids meteor shower occurs from January 13 - January 30. Canes Venatici was named by the Polish astronomer Johannes Hevelius in 1690.
- [Abbreviation: Cap] Capricornus (the goat) is a constellation of the zodiac. Capricorn is seen along the ecliptic between Sagittarius and Aquarius. The brightest stars in Capricornus are Prima Giedi (Alpha 1 Cap) and Secunda Giedi (Alpha 2 Cap). The globular cluster M30 is in Capricorn.
- Cassiopeia is an easily-seen constellation that is in the far northern sky. It circles the pole star (Polaris) throughout the year and also straddles the Milky Way. The five major stars of Cassiopeia (also known as “The Lady of the Chair”) are shaped like a “W” (or an “M,” depending on your orientation). All of the stars in Cassiopeia are all less than second magnitude brightness. The brightest star in Cassiopeia is Schedar (alpha CAS), which is a multiple star that is pale rose in color and varies in magnitude from 2.2 to 2.8 magnitudes. The second-brightest, called Caph (beta CAS), is a white star of magnitude 2.4. Cassiopeia contains two open clusters, M52 (magnitude 7.3) and M103 (magnitude 7.4). The strongest radio source, Cassiopeia A, emanates from Cassiopeia; it is the remnant of a supernova which ocurred about A.D. 1660, and is 10,000 light years from us. The constellation Cassiopeia was named for Cassiopeia, the mother of Andromeda (and the wife of Cephus) in Greek mythology.
- Cepheus is a house-shaped constellation in the Northern Hemisphere. It is a circumpolar constellation; it never dips under the horizon in the Northern hemisphere. Errai (Gamma Cephei) is a third-magnitude orange subgiant star that will become the Earth’s north polar star in 2,000 years. Cepheus is next to the constellations Andromeda and Perseus. Cepheus was named after King Cepheus in Greek mythology, and is abbreviated Cep.
- Cetus is a constellation that straddles the celestial equator. Cetus means whale, and is abbreviated Cet. The first-known variable star Mira, is Omicron Ceti.
- Columba (the dove, abbreviated Col) is a small constellation in the Southern Hemisphere. This constellation pictures a dove holding an olive branch in its mouth. Columba is a member of the “Heavenly Waters,” a family of constellations. Columba was named by the astronomer Bayer, but was populatized by the French astronomer Augustin Royer in 1679 (before that, Colmba’s stars have been included in the constellation Canis Major). Alpha Col (the brightest star in Columba) is called Phaet; beta Col (the second-brightest star in Columba) is called Wezn. The globular cluster NGC 1851 and the blue magnitude 5 star (mu Col, a “runaway star”) are in Columba.
- Crux (or Crux Australis) is the scientific name of the Southern Cross constellation. This well-known, cross-shaped Southern Hemisphere constellation is on the Australian flag. The brightest star in Crux is Acrux (alpha Cru), a double-star system at the base of the cross. The second-brightest star is Becrux or Mimosa (Beta Cru); the third-brightest is Gacrux (Gamma Cru). The Jewel Box (also known as Kappa Crucis) is an open cluster of about 100 stars in the Southern Cross. Crux lies on the Milky Way and is surrounded by the constellation Centaurus on three sides.
- Cygnus (the swan) is a constellation that is shaped like a large cross. It is also known as the Northern Cross. It is seen along the Milky Way in the northern hemisphere. At its tail is the very bright star Deneb (alpha Cygni), and at its head is the double star Albireo (beta Cygni).
- Draco (from the dragon in Greek mythology) is a constellation in the Northern Hemisphere. It is the radiant of the Quadrantids and Draconids (meteor showers). Draco is near the northern celestial pole; the tail of Draco is between the Big Dipper and the Little Dipper. The brightest star in the Draco is Thuban; it is located in the dragon’s tail. (Thuban means “dragon or serpent” in Arabic. Thuban was the Earth’s pole star about 5,000 years ago.) The second-brightest star in the Draco is Rastaban (which means “head of the dragon or serpent”).
- [Abbreviation: Eri] Eridanus (the River) is a southern constellation that is may have been named for the river Nile, the river Euphrates, or for the river of tears wept by the mythical Heliades. Eridanus is located near the constellations Fornax and Lepus. The brightest star in Eridanus, alpha Eri, is Achernar (meaning “end of the river”); it is the 9th brightest star in the sky (magnitude 0.46). The second-brightest, beta Eri, is Cursa (meaning “chair/footstool of Orion” ). The third-brightest, gamma Eri, is Zaurak (meaning “boat” ). The fourth-brightest, delta Eri, is Rana (meaning “frog” ). The fifth-brightest, zeta Eri, is Zibal (part of the “Ostrich’s Nest”). Eridanus was one of the original 48 constellations first noted by Ptolemy
- [Abbreviation: Gem] Gemini (also known as “The Twins”) is one of the constellations of the zodiac, located along the ecliptic between Taurus and Cancer. The brightest stars in Gemini are Castor (a sextuple star - three double stars) and Pollux (a 1st magnitude yellow star). The open cluster M35 is located in Gemini. The Geminid meteor shower seems to radiate from Gemini.
- Hercules is a Northern Hemisphere constellation that is the fifth largest in the sky. It is named for Hercules, the legendary hero of Greek mythology. The brightest of its rather dim stars is Ras Algethi (alpha Her), a variable red supergiant. The four stars of the central trapezoid within Hercules, epsilon Her, zeta Her, eta Her and pi Her, form the asterism called Keystone. The globular star cluster M13 is located on the western part of the Keystone. The Tau Herculid meteor shower seems to radiate from Hercules.
- [Abbreviation: Leo] Leo (the lion) is a constellation of the zodiac that is shaped like a lion. Leo is seen along the Milky Way in the Northern Hemisphere along the ecliptic between Virgo and Cancer. The brightest star (Alpha Leo) in Leo is Regulus (meaning “little king”). The second-brightest star (Beta Leo) is Denebola (meaning “tail of the lion”), and the third-brightest star (Gamma 1 Leo) is Algieba (meaning “forehead”). The spiral galaxies M65, M66, M95, M96, and the elliptical galaxy M105 are nearby.
- [Abbreviation: Lib] Libra (the balance) is a constellation of the zodiac. Libra is seen along the ecliptic between Virgo and Scorpius. The brightest star (Alpha 2 Lib) in Libra is Zuben Elgenubi, the second-brightest star (Beta Lib) is Zuben Elschemali, the third-brightest star (Gamma Lib) is Zuben Elakrab, and the fourth-brightest star (Delta Lib) is Zuben Elakribi.
- Lupus (the wolf) is a constellation in the Southern Hemisphere. It is located between Centaurus to the west, Scorpius to the northeast. The open star cluster NGC 5822 is in Lupus.
- Lyra (the lyre) is a small, bright constellation in the Northern Hemisphere. The brightest star in Lyra is Vega (meaning “falling eagle”) which has a white color and is the fifth brightest star in the sky.
- Orion, also known as “The Hunter,” is a constellation. The brightest stars in Orion are Rigel. Betelgeuse, and Bellatrix. The Horsehead Nebula and the nebulae M42 and M43 (called the Orion nebula) are also in this constellation.
- Pegasus (the flying horse) is a large northern hemisphere constellation. Delta Pegasi is shared with the constellation Andromeda. 51 Pegasi (51 Peg), off the Great Square of Pegasus, is a nearby, Sun-like star that has been found to have an orbiting planet.
- Perseus is a constellation in the Milky Way in the Northen Hemisphere. It is abbreviated Per. Perseus’ major star is alpha Per, called Marfak or Algenib; it is an F5 supergiant. Beta Per is the eclipsing binary Algol. Perseus was a hero in Greek mythology who killed the monstrous Medusa. Each year in August, the Perseid meteor shower radiates from this constellation’s northern part.
- [Abbreviation: Psc] Pisces (the fish) is a faint equatorial constellation of the zodiac. Pisces is seen along the ecliptic between Aries and Aquarius. The brightest star in Pisces (Alpha Psc) is Al Rischa (or Alrisha), the second-brightest-star (Beta Psc) is Fum al Samakah. The spiral galaxy M74 is in Pisces.
- [Abbreviation: Sgr] Sagittarius is the ninth constellation of the zodiac. To the ancients, it represented a centaur (half-man, half-horse) archer who was aiming at the Scorpion (the next constellation) which bit Orion. Its central section (the archer’s chest) also resembles a teapot. The center of the Milky Way Galaxy is in the direction of Sagittarius. Many meteor showers, including the Sagittariids, seem to radiate from Sagittarius. The brightest star in Sagittarius (Alpha Sgr) is Rukbat (which means “knee” in Arabic).
- [Abbreviation: Sco] Scorpius (the scorpion) is a constellation of the zodiac. This constellation is seen along the ecliptic between Libra and Sagittarius. The brightest star in Scorpius is Antares, a red supergiant star that is about 500 light-years away from Earth and is about 230 times as big as the Sun. The second-brightest (Beta 1 Sco) is Graffias.
- Southern Cross
- Crux is the scientific name of the Southern Cross constellation. This well-known, cross-shaped Southern Hemisphere constellation is on the Australian flag. The brightest star in Crux is Acrux, a double-star system at the base of the cross. This constellation lies on the Milky Way and is surrounded by the constellation Centaurus on three sides. It is abbreviated Cru.
- [Abbreviation: Tau] Taurus (the bull) is a constellation of the zodiac. This constellation is seen along the ecliptic between Aries and Gemini. The brightest star (Alpha Tau) in Taurus is Aldebaran, which is one of the bull’s eyes (Aldebaran is the 13th brightest star in the sky). The second-brightest star in Taurus (Beta Tau) is Alnath, the third brightest (Gamma Tau) is Hyadum I.
- Ursa Major
- Ursa major (The Great Bear) is a well-known constellation in the Northern Hemisphere that contains the 7 stars of the Big Dipper.
- Ursa Minor
- Ursa minor (The Little Bear) is a Northern Hemisphere constellation that is also known as the Little Dipper. This group of stars starts at Polaris, the pole star of the Northern Hemisphere
- [Abbreviation: Vir] Virgo (the virgin) is a constellation of the zodiac. It is located along the ecliptic between Leo and Libra. Virgo is seen along the ecliptic. The brightest star in Virgo is Spica (meaning “ear of wheat”). Virgo is the second-largest constellation (of the 88 constellations), after Hydra.