High Quality Content by WIKIPEDIA articles! In 2006, the International Astronomical Union (IAU) defined a planet as a body in orbit around the Sun that was large enough to have achieved hydrostatic equilibrium and to have cleared the neighbourhood around its orbit. An object in hydrostatic equilibrium is one that is large enough for its gravity to have overcome its internal rigidity, and so relax into a rounded (ellipsoidal) shape. The practical meaning of "cleared the neighborhood" is that a planet is comparatively massive enough for its gravitation to control the orbits of all objects in its vicinity. By the IAU''s definition, there are eight planets in the Solar System. Those objects in orbit around the Sun that have achieved hydrostatic equilibrium but have not cleared their neighborhoods are classified as dwarf planets, and the remainder are termed small Solar System bodies. In addition, the Sun itself and 19 known natural satellites are also massive enough to have achieved hydrostatic equilibrium. All known objects in the Solar System with a hydrostatic shape are listed below, with a sample of the largest objects whose shape has yet to be accurately determined. The Sun''s orbital characteristics are listed in relation to the Galactic Center. All other objects are listed in order of their distance from the Sun.
