Dwarf planet
A
dwarf planet is an object the size of a planet but that is neither a planet nor a moon or other natural satellite. More explicitly, the International Astronomical Union defines a
dwarf planet as a celestial body in direct orbit of the Sun[1] that is massive enough for its shape to be controlled by gravity, but that unlike a planet has not cleared its orbit of other objects.[2][3] The term
dwarf planet was adopted in 2006 as part of a three-way categorization of bodies orbiting the Sun,[1] brought about by an increase in discoveries of trans-Neptunian objects that rivaled Pluto in size, and finally precipitated by the discovery of an even more massive object, Eris.[4] This classification states that bodies large enough to have cleared the neighbourhood of their orbit are defined as
planets, whereas those that are not massive enough to be rounded by their own gravity are defined as
small Solar System bodies. Dwarf planets come in between.