A dwarf planet is a celestial body that -orbits the sun, has enough mass to assume a nearly round shape, has not cleared the neighborhood around its orbit and is not a moon. In 2006, with the discovery of several other rocky bodies similar in size or larger than Pluto, the IAU decided to re-classify Pluto as a dwarf planet. Despite its small size — 0.2 percent the mass of Earth and only 10 percent the mass of Earth's moon — Pluto's gravity is enough to capture five moons of its own.