A planet () is an astronomical object] [[orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.This definition is drawn from two separate IAU declarations; a formal definition agreed by the IAU in 2006, and an informal working definition established by the IAU in 2001/2003 for objects outside of the Solar System.
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