Comets are large pieces of rock and ice that come from a place beyond the solar system. This place is known as the Oort Cloud. Some comets can be up to 10 miles wide! As they come towards the sun they are visible from Earth. They have two tails. One tail is blue and has gas and dust flying out into space behind it. The other is yellow and curved. The comet circles the sun in an elliptical orbit and does not return for a long time, sometimes thousands of years! Halley's Comet, discovered by Edmond Halley in 1705, is a comet that orbits the sun every 75 years or so. It is named after Halley because he predicted the next time that the comet would be visible.
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