planet science definition

1. In the traditional model of solar systems, a celestial body larger than an asteroid or comet, illuminated by light from a star, such as the Sun, around which it revolves.
2. A celestial body that orbits the Sun, has sufficient mass to assume nearly a round shape, clears out dust and debris from the neighborhood around its orbit, and is not a satellite of another planet. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was considered to be a planet until its reclassification in 2006 as a dwarf planet.  A planetlike body with more than about ten times the mass of Jupiter would be considered a brown dwarf  rather than a planet. See also extrasolar planet, inner planet, outer planet.

Related Forms:

• planetary planetary adjective