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Astronomy: Asteroid belt
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Thousands of asteroids (also called planetesimals) swarm across the 35 million kilometers of space between the planets Mars and Jupiter. This 'asteroid belt' marks the junction between the inner and outer Solar System and houses 90 - 95% of all asteroids. Other asteroids can be found in the Edgeworth-Kuiper Belt. The origin of the asteroid belt is not quite clear. One theory suggests that the strong gravity of Jupiter kept the planetesimals from forming a planet. Another theory suggests that once there was a planet between Mars and Jupiter, but it was destroyed in earlier times. Suggestions about a large impact of another body, or a civilization that destroyed itself make this a nice story, but impossible to prove. Other asteroids orbit close to the Sun and some have been captured by the gravity of planets like Jupiter, Mars and the Earth. Some asteroids have others revolving around them, just as the Moon revolves around the Earth. Ida, an asteroid about 56km in diameter has its own moon - a tiny body only 1km in size. Other asteroids may well have moons of their own, waiting to be discovered. Some asteroids travel in pairs, spinning around a common centre of gravity. These are called 'binaries'. Astronomers were surprised by this, because they thought their gravity would be too weak to bind them together. But this discovery solved the mystery of why impact craters often appear in pairs on the Earth. Related subjects>> Other planetesimals: the Edgeworth-Kuiper Belt>> Official Near Earth Asteroid Tracking System internetsite >> Official Space Guard Programme internetsite |
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