orbit

Path of one body in space around another, such as the orbit of the Earth around the Sun or of the Moon around the Earth. Both bodies move around their common centre of mass. The movement of objects in orbit follows Kepler's laws, which apply to artificial satellites as well as to natural bodies.

As stated by the laws, the orbit of one body around another is an ellipse. The ellipse can be highly elongated, as are comet orbits around the Sun, or it may be almost circular, as are those of some planets. The closest point of a planet's orbit to the Sun is called perihelion; the most distant point is aphelion. (For a body orbiting the Earth, the closest and furthest points of the orbit are called perigee and apogee.)