Τhe myth
In Greek mythology, Andromeda was the daughter of Cepheus and Cassiopeia, king and queen of the kingdom Aethiopia.

Her mother Cassiopeia boasted that her daughter was more beautiful than the Nereids, the nymph-daughters of the sea god Nereus and often seen accompanying Poseidon. To punish the queen for her arrogance, Poseidon, brother to Zeus and god of the sea, sent a sea monster named Cetus to ravage the coast of Aethiopia including the kingdom of the vain queen. The desperate king consulted the Oracle of Apollo, who announced that no respite would be found until the king sacrificed his daughter, Andromeda, to the monster. Stripped naked, she was chained to a rock on the coast.

Perseus was returning from having slain the Gorgon Medusa. After he happened upon the chained Andromeda, he approached Cetus while invisible (for he was wearing Hades’s helm), and killed the sea monster. He set Andromeda free, and married her.

After Andromeda’s death, at about 412 BCE according to Euripides, Athena placed her among the constellations in the northern sky, near Perseus and Cassiopeia; the constellation of Andromeda, so known since antiquity, is named after her.

Τhe constellation
Andromeda is a galaxy of 4000 stars (a mg 3,47). The galaxy is known as Massier 31, a rotating nebula in spiral form located south of Cassiopeia among the constellations of Pegasus and Perseus approximately 2310000 light years from our earth. The Milky Way is moving towards the Andromeda nebula. Studies on the halo of the Andromeda galaxy suggest that it is very similar to that of our Milky Way and is the most distant nebula can be distinguished by the naked eye.