40 people bested this!
1 person is curious.
Pluto is a dwarf planet in the solar system, orbiting 29 – 49 AU from the Sun. About a fifth the mass of the Moon, Pluto is primarily composed of rock and water ice. It has an eccentric orbit that is highly inclined with respect to the planets and takes it closer to the Sun than Neptune during a portion of its orbit. Pluto and its largest satellite Charon have often been considered a binary system because they are more nearly equal in size than any of the planet/moon combinations in the solar system, and because the barycentre of their orbits does not lie within either body. Two smaller moons named Nix and Hydra were discovered in 2005. Pluto is smaller than several of the natural satellites or moons in our solar system (see the list of solar system objects by radius).