What is a Planet? Definition, Characteristics, and Types

Planet definition, a celestial body larger than a meteoroid and smaller than a star, having a discernible atmosphere, and orbiting a star. See more.
A planet is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape (i.e., it is nearly round in shape), (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.
Planet Definition. A planet is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape (i.e., it is nearly round in shape), (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.
A planet is a celestial body that orbits a star or stellar remnant, and has enough mass to assume a hydrostatic equilibrium shape, meaning it is nearly round in shape. The definition of a planet was revised by the International Astronomical Union (IAU) in 2006 to exclude Pluto and reclassify it as a dwarf planet.