The asteroid belt is a doughnut-shaped concentration of asteroids orbiting the Sun between the orbits of Mars and Jupiter, closer to the orbit of Mars. Most asteroids orbit from between 186 million to 370 million miles (300 million to 600 million km or 2 to 4 AU) from the Sun. The asteroids have a slightly elliptical orbit. The time for one revolution around the Sun varies from about three to six Earth years.
The strong gravitational force of the planet Jupiter shepherds the asteroid belt, pulling the asteroids away from the Sun, keeping them from careening into the inner planets
Asteroids are rocky or metallic objects, most of which orbit the Sun in the asteroid belt between Mars and Jupiter. A few asteroids approach the Sun more closely. None of the asteroids have atmospheres.
Asteroids are also known as planetoids or minor planets.
Asteroids - From The Astronomy Dictionary
