Asteroids, sometimes called minor planets, are rocky, airless remnants left over from the early formation of our solar system about 4.6 billion years ago.
The current known asteroid count is: .
Most of this ancient space rubble can be found orbiting the Sun between Mars and Jupiter within the main asteroid belt. Asteroids range in size from Vesta — the largest at about 329 miles (530 kilometers) in diameter — to bodies that are less than 33 feet (10 meters) across. The total mass of all the asteroids combined is less than that of Earth's Moon.
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The total mass of all the asteroids in the main asteroid belt combined is less than that of Earth's Moon.
NASA Space Place: All About Asteroids ›
Asteroids are small, rocky objects that orbit the Sun. Although asteroids orbit the Sun like planets, they are much smaller than planets.
There are lots of asteroids in our solar system. Most of them live in the main asteroid belt—a region between the orbits of Mars and Jupiter.
Some asteroids go in front of and behind Jupiter. They are called Trojans. Asteroids that come close to Earth are called Near Earth Objects, NEOs for short. NASA keeps close watch on these asteroids.
Asteroids are left over from the formation of our solar system.
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