The discovery of Kuiper belt object (KBO) 2003 UB313, now officially named Eris, prompted the recent reevaluation of Pluto's status as a planet and the creation of a new category called "dwarf planets": objects in orbit around the Sun that are large enough to be in hydrostatic equilibrium but have insufficient mass to gravitationally dominate their region of the solar system. Eris is larger than Pluto (2, 3) and thus the largest currently known member of dwarf planets.
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