Asteroid

Asteroid, planetoid, or minor planet of irregular shape, orbiting the sun. Ranging in diameter from a few feet (1 m) to Ceres's 470 mi (750 km), most (some 50,000 that are too small to yield to diameter measurements) lie in the asteroid belt between the orbits of Mars and Jupiter, their total mass estimated to be 0.001 that of the earth. Ceres was the first to be discovered (1801 by Giuseppe Piazzi), and Vesta is the only one visible to the naked eye. The Apollo asteroids have highly elliptical, earth-approaching orbits, and may have caused several of earth's meteorite craters. The Trojan asteroids share the orbit of the planet Jupiter.