Kuiper BeltOn August 23, 2006, the International Astronomical Union(IAU, the official authority responsible for naming stars, planets, celestial bodies and phenomena, etc.---the official body of astronomy) re-classified Pluto as a "dwarf planet". A "planet" in our solar system is a celestial body that "(a) orbits the Sun; (b) has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape; and (c) has cleared the neighborhood around its orbit." Pluto fits (a) and (b), but not (c). Pluto, Eris, Ceres, and others will be called "dwarf planets" because although they fit (a) and (b), they have not cleared the neighborhood around their orbits. Also, a "dwarf planet" is not a satellite (which may leave out Charon, but its large mass compared to Pluto may make Charon to be a "dwarf planet"). The third criteria (c) of a planet from the IAU has caused a considerable amount of debate---what does "cleared the neighborhood around its orbit" mean? One interpretation is to say that the
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