The International Astronomical Union is about to decide the Solar System has 12 planets. The new planets: Xena would become the most distant planet. Charon would become a planet. Since Pluto and Charon both orbit a point in space outside of both, Pluto and Charon become a double planet system. Ceres, the first and largest asteroid discovered, becomes the solar system's smallest planet. Actually, when Ceres was first discovered, it was classified as a planet and was later downgraded to asteroid status. http://news.yahoo.com/s/space/20060816/sc_space/nineplanetsbecome12withcontroversialnewdefinition [Broken] Don't expect the number to remain at 12 very long. The number of planets in the solar system will jump to anywhere from 24 to 53 fairly quickly, with the number eventually rising into the hundreds or thousands. The new definition is pretty simple: "A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet." (Charon isn't a satellite of Pluto since the two orbit a point in space outside of both objects).