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Asteroids Comets Meteors and Meteorites
Asteroids or planetoids are swarms of tiny bodies revolving around the sun mostly between the orbits of Jupiter and Mars. The largest among the asteroids is the Geres.
Comets differ a great deal from the planets. They are made up of very tenuous material and actually contain very little mass. They are believed to be originating from a vast cloud of matter which completely surrounds the solar system and stretches out from just beyond the orbit of Pluto to a distance of about two light years. This matter is known as Oort's Cloud. The gravitational pull of the passing stars releases clumps of matter from this cloud setting them off towards the inner reaches of the solar system in the form of comets. They become visible only when they reach close to the sun. One of the most famous comets, Haily's Comet appears every 76 years. Many of the comets, however, are unpredictable. The tail of a comet is made up of low density gas.
Meteors and Meteorites
Meteors and meteorites appear as shooting stars in the night sky. Many of them have a very close relationship with comets. They are some moving objects in the solar system which get attracted towards the earth due to its gravitational force and enter the atmosphere of the earth. As they pass through the atmosphere of the earth at a great velocity the friction generated causes them to get heated and start glowing. Usually they are completely burnt before they can reach the surface of the earth. However, a few of them may reach the surface of the earth and hit the earth with great force forming huge craters where they strike. They are called meteorites.