American astronomer who, with Jane Luu, discovered several small, icy bodies in orbit between planets Neptune and Pluto. Prior to this discovery, the presence of many "Kuiper Belt" objects was predicted. It has even been suggested that Pluto may simply be the largest object in the Kuiper Belt and not a bona fide planet after all. The Kuiper Belt, a ring of comets and other small celestial objects beyond the orbit of Neptune, is thought to be home to many short-period comets, such as Halley's Comet.