Orcus

Orcus is a dwarf planet candidate in the Kuiper belt with one large moon, Vanth, and an estimated diameter between 870 and 960 kilometers, comparable to the inner Solar System dwarf planet Ceres. Its surface is relatively bright, with an albedo reaching about 23 percent, neutral in color and rich in water ice that is mostly crystalline, a state that may point to past cryovolcanic activity, with methane or ammonia possibly present as well. It was discovered on 17 February 2004 by the American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz.