Oberon is named for Shakespeare's King of the Fairies from "A Midsummer Night's Dream." It is the second largest moon of Uranus, and was first studied when NASA's Voyager 2 flew by in 1986. This photo, taken by Voyager 2, shows "several large craters in Oberon's icy surface surrounded by bright rays similar to those seen on Jupiter's moon Callisto." Like the rest of Uranus' large moons, Oberon is mostly made of ice and rock. It was first discovered in 1787 by astronomer William Herschel. At present, Uranus has about 27 named moons.