The International Astronomical Union (IAU) divides the sky into 88 official constellations with precise boundaries, so that every direction belongs to exactly one constellation. These are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages.
The zodiac includes the following 12:
- Aries, the ram
- Taurus, the bull
- Gemini, the twins
- Cancer, the crab
- Leo, the lion
- Virgo, the virgin
- Libra, the scales
- Scorpius (also called Scorpio), the scorpion
- Sagittarius, the archer
- Capricornus (also called Capricorn), the sea goat
- Aquarius, the water carrier
- Pisces, the fish
- Andromeda
- Aquila, the eagle
- Ara, the altar
- Argo Navis, the ship of the argonauts, since divided into Carina, Puppis and Vela
- Auriga, the charioteer
- Boötes, the herdsman
- Canis Major, the greater dog
- Canis Minor, the lesser dog
- Cassiopeia
- Centaurus, the centaur
- Cepheus
- Cetus, the whale
- Corona Australis, the southern crown
- Corona Borealis, the northern crown
- Corvus, the raven
- Crater, the cup
- Cygnus, the swan
- Delphinus, the dolphin
- Draco, the dragon
- Equuleus, the little horse
- Eridanus, the river
- Hercules
- Hydra, the sea monster
- Lepus, the hare
- Lupus, the wolf
- Lyra, the lyre
- Ophiuchus, the serpent-bearer - actually intersects the ecliptic
- Orion, the hunter
- Pegasus
- Perseus
- Piscis Austrinus, the southern fish
- Sagitta, the arrow
- Serpens, the serpent
- Triangulum, the triangle
- Ursa Major, the greater bear
- Ursa Minor, the lesser bear
- Antlia, the pump
- Apus, the bird of paradise
- Caelum, the chisel
- Camelopardalis, the giraffe
- Canes Venatici, the hunting dogs
- Chamaeleon
- Circinus, the drawing compasses
- Columba, the dove
- Coma Berenices (traditional asterism), Berenice's hair
- Crux, the cross
- Dorado, the swordfish
- Fornax, the furnace
- Grus, the crane
- Horologium, the clock
- Hydrus, the water snake
- Indus, the Indian
- Lacerta, the lizard
- Leo Minor, the lesser lion
- Lynx
- Mensa - originally Mons Mensae, table mountain
- Microscopium, the microscope
- Monoceros, the unicorn
- Musca, the fly
- Norma, the square
- Octans, the octant
- Pavo, the peacock
- Phoenix
- Pictor - originally Equuleus Pictoris, the painter's easel
- Pyxis, the compass
- Reticulum, the reticle
- Sculptor
- Scutum, the shield
- Sextans, the sextant
- Telescopium, the telescope
- Triangulum Australe, the southern triangle
- Tucana, the toucan
- Volans - originally Piscis Volans, the flying fish
- Vulpecula - originally Vulpecula Cum Ansere, the fox with the goose
- the Big Dipper in Ursa Major;
- the Little Dipper in Ursa Minor;
- the Teapot in Sagittarius,
- Orion's belt;
- the Summer Triangle (Deneb, Altair, and Vega, or α Cygni, Aquilaee, and Lyrae);
- the Great Square of Pegasus (which includes α Andromedaee);
- the Urn in Aquarius;
- the Sickle in Leo.
See also: list of constellations by area