Callisto

(kə-lĭsˈtō)

1. Greek Mythology A nymph, beloved of Zeus and hated by Hera. Hera changed her into a bear, and Zeus then placed her in the sky as the constellation Ursa Major.
2. One of the four brightest satellites of Jupiter and the eighth in distance from the planet. Originally sighted by Galileo, it is the largest planetary satellite.