Oberon (moon) the spacecraft "Voyager 2" took several images of Oberon in January 1986, allowing 40% of the moon's surface to be mapped. Oberon was discovered by William Herschel on January 11, 1787; on the same day he discovered Uranus's largest moon, Titania. He later reported the discoveries of four more satellites, although they were subsequently revealed as spurious. For nearly fifty years following their discovery, Titania and Oberon would not be observed by any instrument other than William Herschel's, although the moon can be seen from Earth with a present-day high-end amateur telescope. All of the moons of Uranus are named
Definition of planet the Solar System. After 1992, however, astronomers began to discover many additional objects beyond the orbit of Neptune, as well as hundreds of objects orbiting other stars. These discoveries not only increased the number of potential planets, but also expanded their variety and peculiarity. Some were nearly large enough to be stars, while others were smaller than Earth's moon. These discoveries challenged long-perceived notions of what a "planet" could be. The issue of a clear definition for "planet" came to a head in January 2005 with the discovery of the trans-Neptunian object Eris, a body more massive than the smallest