Orbit

Orbit, path followed by 1 celestial body revolving under the influence of gravity about another. In the solar system, the planets mainly orbit the sun, and the moons the planets, in elliptical paths. The point in the planetary, asteroidal, or cometary orbit closest to the sun is called its perihelion; the farthest point is termed the aphelion. In the case of a moon or artificial satellite orbiting a planet or other moon, the corresponding terms are perigee and apogee. Celestial objects of similar masses, particularly double stars, may orbit each other.