In Roman mythology, Jupiter (the king of the gods) lusts after a young woman named Callisto, a nymph of Diana. Juno, Jupiter's jealous wife, discovers that Callisto has a son named Arcas, and believes it is by Jupiter. Juno then transforms the beautiful Callisto into a bear so she no longer attracts Jupiter. Callisto, while in bear form, later encounters her son Arcas. Arcas almost shoots the bear, but to avert the tragedy, Jupiter turns Arcas into a bear too and puts them both in the sky, forming Ursa Major and Ursa Minor. Callisto is Ursa Major and her son, Arcas, is Ursa Minor. In ancient times the name of the constellation was Helike, ("turning"), because it turns around the Pole. In Book Two of Lucan it is called Parrhasian Helice, since Callisto came from Parrhasia in Arcadia, where the story is set. The Odyssey notes that it is the sole constellation that never sinks below the horizon and "bathes in the Ocean's waves", so it is used as a celestial reference point for navigation. It is also referred to as the "Wain".
The smaller bear is represented by Ursa Minor . Ursa Major is the largest northern constellation and third largest constellation in the sky. Its brightest stars form the Big Dipper asterism, one of the most recognizable shapes in the sky, also known as the Plough. Ursa Major is well-known in most world cultures and associated with a number of myths. It was one of the constellations catalogued by the Greek astronomer Ptolemy in the 2nd century. In Greek mythology, it is associated with Callisto, a nymph who was turned into a bear by Zeus’ jealous wife Hera.