Ursa Major and Callisto: the nymph who never sets
Callisto turned into a bear, her son Arcas and Hera's revenge: the Greek myth of Ursa Major, the Plough or Big Dipper and the seven oxen of the north.
For anyone living in the northern hemisphere, Ursa Major is the most familiar constellation. The seven stars of the Plough, or Big Dipper, are visible all year round, wheel around the pole and never sink below the horizon at Mediterranean latitudes. The ancient Greeks wondered why that figure never bathed in the waters of Ocean, as all the others did, and found the answer in one of the most painful stories in mythology.
The nymph of Artemis
Callisto, whose name means “the most beautiful”, was the daughter of Lycaon, king of Arcadia, and a hunting companion of Artemis. Like all the goddess's followers she had taken a vow of chastity. Zeus, however, fell in love with her and, according to Ovid's account in the Metamorphoses, approached her by taking on the appearance of Artemis herself. From the union a son was born, Arcas, and when the pregnancy was discovered Callisto was driven out of the band of huntresses.
The sources disagree about who turned her into a bear: for some it was Hera, jealous of her husband; for others Artemis, offended by the broken vow; for others still Zeus himself, trying to hide her. For years Callisto wandered the woods in animal form. When Arcas, now grown and a hunter, met her, he did not recognise her and raised his spear to strike. Zeus intervened and placed mother and son among the stars.
The ban of Ocean
In many versions Arcas became the constellation Boötes, the “herdsman”, whose chief star, Arcturus, means “guardian of the bear”. Hera did not accept the honour granted to her rival and asked the sea deities Oceanus and Tethys never to receive the bear into their waters. This, says the myth, is why Ursa Major never sets: a poetic explanation of its circumpolar position.
Homer himself, in the Iliad, describing the shield of Achilles, mentions the Bear that men also call the Wain, the only one “without share in the baths of Ocean”. The double image of bear and wagon is therefore very ancient, and in Greece the two names, Arktos and Hamaxa, coexisted for centuries. From the first comes our adjective “arctic”: the Arctic regions are, literally, the lands lying beneath the Bear.
The seven oxen and the travellers' guide
The Romans saw in these stars seven yoked oxen, the septem triones, turning slowly around the pole as around a threshing floor. From this expression comes the Italian word “settentrione”, used for the north. Two stars of the Plough, Dubhe and Merak, point the way to the Pole Star: extending the distance between them about five times leads to the small star that marks the north.
In the handle of the Plough the star Mizar has a fainter companion beside it, Alcor, and tradition long regarded the ability to tell them apart as a test of good eyesight. The same group of stars has been read elsewhere as a plough, a ladle or a funeral bier, a sign of how universal attention to this figure has been.
Ursa Major carries into the sky a story of unwilling guilt and missed reconciliation, in which a mother and a son are saved only by being turned into stars. Every night their rotation around the pole recalls the journey of Callisto, condemned never to rest in Ocean and at the same time destined never to vanish from human sight.