Pluto is considered a dwarf planet and the largest object of the Kuiper belt. Pluto is only 1/6th the size of Earth and is smaller than the Moon. Although Pluto was considered as a planet, many bodies orbiting in the same volume as Pluto have been discovered. The data demonstrated that Pluto is part of a set of objects called the Kuiper belt. According to the definition a planet (1) is the object in orbit around the Sun, (2) is massive enough to be rounded by own gravity, and (3) has a clear neighborhood around its orbit (except its satellites). It was decided that Pluto does not meet the third criteria due to the presence of several other objects with the same size near Pluto (i.e., Eris). As a result, Pluto, as well as Eris and some other objects in the Kuiper belt, has been classified as a dwarf planet.