A celestial body is any natural object in space, such as an ASTEROID, PLANET, STAR, COMET, SUN, or SATELLITE. An ASTEROID is a small rocky body orbiting the SUN, while MARS is the fourth PLANET from the SUN. A STAR is a luminous ball of gas that produces energy from nuclear fusion reactions. A COMET is a small icy body that orbits the SUN and has a visible coma and tail when close to the SUN. The SUN is the STAR at the center of our solar system, and an ORB is a round object or body. A PLANET is a celestial body that orbits the SUN and has enough mass to assume a nearly round shape. Finally, a SATELLITE is an object that orbits another object in space.