Asteroids are small, rocky, irregular bodies
orbiting the sun. The first asteroid was discovered by Giuseppe Piazzi in 1801.
He originally thought he had found a comet, but found that its orbit more
closely matched those of planets rather than comets. He named the object Ceres.
Ceres is the largest of all known asteroids. It is 933 km in diameter and
contains about 25% of the mass of all the asteroids. The asteroids together
have a mass less than that of the Moon.
The majority of the known asteroids exist between Mars and Jupiter. This area contains over 4,000 numbered bodies. This area is unique because the asteroids did not form a planet. Jupiter's early formation may have affected this area by either sweeping up or ejecting many of the bodies.
Asteroids within the asteroid belt, or Main Belt asteroids are divided into subgroups named after the main asteroid of the subgroup. Asteroids not within the Main Belt are either Near Earth Asteroids or Trojans, which are asteroids near Jupiter.
