ETYM Old Eng. planete, French plančte, Latin planeta, from Greek planes a planet; prop. wandering, from planasthai to wander.
Any of the celestial bodies (other than comets or satellites) that revolve around the sun in the solar system.
Large celestial body in orbit around a star, composed of rock, metal, or gas. There are nine planets in the Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune, Uranus, and Pluto. The inner four, called the terrestrial planets, are small and rocky, and include the planet Earth. The outer planets, with the exception of Pluto, are called the major planets, and consist of large balls of rock, liquid, and gas; the largest is Jupiter, which contains more than twice as much mass as all the other planets combined. Planets do not produce light, but reflect the light of their parent star.
As seen from the Earth, all the historic planets are conspicuous naked-eye objects moving in looped paths against the stellar background. The size of these loops, which are caused by the Earth's own motion round the Sun, are inversely proportional to the planet's distance from the Earth.