Pluto is a dwarf planet that usually orbits beyond the orbit of Neptune. It was discovered by Clyde Tombaugh on Feb. 18, 1930 (Pluto was considered to be a planet from its discovery until 2006, when it was reclassified as a dwarf planet; there are many smaller dwarf planets in our Solar System).
Pluto has one large moon, Charon, that is close in size to Pluto. Two very tiny moons were discovered in 2005.
Pluto is smaller than a lot of the other planets' moons, including our moon (Pluto may actually be an asteroid). Pluto has not been visited by spacecraft yet; we only have blurry pictures of its surface. Pluto's composition is unknown. It is probably made up of about 70% rock and 30% water (this is determined from density calculations).
