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# Write a note on Asteroids.

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* Asteroids are rocks with irregular shape(s) revolving around sun, which failed to assemble into planets (form planets) during the formation of the solar system.
* They are found in the belt between the orbits of Mars and Jupiter.
* There are about 1 lakh (0.1 million) asteroids.
* Orbits of about 4000 asteroids are known.
* Ceres is the largest asteroid known and it was the first asteroid to be discovered. Its diameter is about 1000 km.
* Vesta is another asteroid which is luminous and has diameter of about 400 km. It was discovered in 1807 AD.
* During their movement around sun, they sometimes collide with one another and get broken.
* The debris of asteroids sometimes enters earth's atmosphere in the form of meteors which burn out due to atmospheric friction.
* If a meteor is very large, it reaches the earth's surface. Then it is called a meteorite.
* Asteroids contain silicon, nickel, chromium and calcium with possibly gold and platinum.