Callisto

Callisto was another maiden who made Juno jealous. To take away her beauty, she decided to turn her into a bear.

So Callisto was a bear, unable to call for help, and all by herself in the forest. One day she came upon a young man who was hunting. He was about to kill her, but a god intervened and made them both stars; known today as the Little Bear and the Great Bear.

Yet Juno was angry that her attempt to destroy Callisto had gone so badly, and she asked the powers of the ocean not to allow the two bears to sink in the ocean with the other stars, which is why those two constellations wander around heaven but never sink down to the sea with the other ones.

I read another myth on why the Great and Small Bears were formed, from the Native Americans. I liked that one better, because it had more details and more adventure.