What is the mythology of Ursa Major the group of stars commonly known as the Big Dipper?

Ursa Major, the great bear, was supposed to be a nymph called Callisto. She was vowed to the service of the goddess Artemis, and was supposed to remain a virgin. However she was seduced/tricked (depending on the version of the myth) by Zeus and bore a son, Arcas. Hera, out of jealousy transformed her into a bear. Years later, Arcas, unknowing, was about to shoot her when Zeus saved her by turning Arcas into a bear too. He placed them both in the sky, with Arcas becoming the Little Bear, Ursa Minor.