Most of the constellation names we still use come from ancient Greece. The Greeks took many figures from the Babylonians and linked them to their own myths: a hero, animal or object was "placed among the stars" by the gods as a reward or memorial. This was called catasterism. In the 2nd century AD the astronomer Ptolemy listed 48 constellations in the Almagest; the International Astronomical Union now recognises 88, and all of Ptolemy's are still among them.
| Constellation | Myth | Best seen (northern hemisphere) |
|---|---|---|
| Orion | The giant hunter, killed by the Scorpion | Winter |
| Scorpius | The scorpion sent by Gaia against Orion | Summer |
| Ursa Major | The nymph Callisto turned into a bear | All year |
| Ursa Minor | Callisto's son, Arcas | All year |
| Perseus | The hero who killed Medusa | Autumn |
| Andromeda | The princess rescued by Perseus | Autumn |
| Cassiopeia | The vain queen, Andromeda's mother | All year |
| Pegasus | The winged horse | Autumn |
| Lyra | The lyre of Orpheus | Summer |
| Hercules | Heracles, hero of the twelve labours | Summer |
| Cygnus | Zeus as a swan, seducing Leda | Summer |
| Gemini | Castor and Pollux, the Dioscuri | Winter |
Orion and the Scorpion
Orion was a giant hunter who boasted he could kill every animal on earth. Gaia, the Earth, sent a scorpion that stung him to death. Zeus set both in the sky, but on opposite sides: when Scorpius rises in the east, Orion sets in the west, as if still fleeing. The three stars in a row at Orion's centre form his famous "belt".
Perseus's family
In autumn one patch of sky tells a whole myth. Queen Cassiopeia boasted that her daughter Andromeda was lovelier than the Nereids; Poseidon sent a sea monster, Cetus, and Andromeda was chained to a rock as a sacrifice. Perseus, returning with Medusa's head, saved her. They are all in the sky: Cassiopeia (the "W"), King Cepheus, Andromeda, Perseus, the horse Pegasus and the Whale (Cetus).
The Milky Way
In one myth Zeus put the baby Heracles to the breast of the sleeping Hera so he would become immortal. Hera woke and pushed him away: the milk sprayed across the sky, forming the Milky Way. The Greek galaxias comes from gala, milk: hence the word galaxy.
The Pleiades
The Pleiades were seven sisters, daughters of the Titan Atlas. Pursued by Orion, they were turned by Zeus into doves and then stars. Six can be seen with the naked eye: the seventh, it was said, hides in shame or grief. Hesiod told farmers to reap when the Pleiades rose, in May, and plough when they set, in November.
The planets
The planets have Latin names, but they match Greek gods: Mercury is Hermes, Venus is Aphrodite, Mars is Ares, Jupiter is Zeus, Saturn is Cronus. The moons of Jupiter discovered by Galileo bear the names of Zeus's loves: Io, Europa, Ganymede and Callisto.
See also metamorphoses and Greek mythology.