Why is there an asteroid belt?

Some asteroids are large, solid bodies — there are more than 16 in the belt with a diameter greater than 150 miles (240 km). The largest asteroids, Vesta, Pallas and Hygiea, are 250 miles (400 km) long and bigger. The region also contains the dwarf planet Ceres. read more

The asteroid belt encompasses an area between 2 and 4 astronomical units from the Sun. The belt was formed 4.6 million years ago, when either the gravitational stress of Jupiter or a collision likely destroyed a planet or protoplanet roughly half the size of the Moon. read more

Most of these objects, called planetoids or asteroids — meaning"star-like" — orbit between Mars and Jupiter in a grouping known as the Main Asteroid Belt. The Main Asteroid Belt lies more than two-and-a-half times as far as Earth does from the sun. read more

The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids. About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. read more