Pluto was discovered in 1930 and was awarded the position of the 9th planet in the solar system. However, in 2006 it was re-classified as a dwarf planet, as a result of the discovery of at least one larger Kuiper Belt object. The orbit of the planet around the Sun - taking nearly 250 years - is quite eccentric. At times this eccentricity brings it closer to the sun than Neptune. Pluto has three moons, the largest named Charon (pronounced KA-ron) is over half the diameter of Pluto. The otheres are named Nix and Hydra and are much smaller. All three can be seen in this HST image.