the solar system
Asteroids are dry, dusty lumps, made of rock, metal, or a mix of both, that orbit the sun. If their paths cross, asteroids can collide, break up, and be set on a path toward Earth. a chunk of asteroid landing on earth is termed a meteorite.
There are over a billion asteroids, and more than 200,000 have been discovered so far. Asteroids are material that failed to form a rocky planet some 4.6 billion years ago when the solar system's planets formed. They are mostly irregular in shape and range in size from several hundred miles across, down to
The Main Belt, the Trojans, and some individual asteroids are shown here. All asteroids orbit close to the planetary plane, in the same direction as the planets. Asteroids in the Main Belt take about 3-6 years to orbit. They spin as they orbit, in just hours.
boulder, pebble, and dust size. About 100 are larger than 125 miles (200 km).
over 90 percent of asteroids are in the main belt, also known as the asteroid belt. Ceres, the largest object in the Main Belt, was reclassified as a dwarf planet in 2006. Although the belt has more than a billion asteroids measuring over 1.25 miles (2 km) long, it is not crowded; thousands of miles separate asteroid from asteroid. the near-earth asteroids have orbits that take them outside the belt. the trojans are two groups that follow Jupiter's orbit, one ahead of the planet, the other behind.
both groups follow Jupiter's orbital period
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