Where do comets come from ? 

Oort Cloud (Artist's Impression)

Trillions of comet nuclei are stored at the edge of our solar system. This cloud of comets, called the Oort cloud in honour of the Dutch astronomer who proposed this idea first. It is thought to be at a distance of more than one trillion kilometers (one followed by twelve zeros) from the earth and the sun. Comet nuclei may also be found in a second location that is much closer viz., the Kuiper belt, a region between the orbits of Neptune and Pluto. About a billion comets may be stored here. Notice that both locations are very far away from the sun. At the low temperatures found at these locations comet nuclei remain frozen mud balls! They are so tiny and so dark that they cannot be detected even with the most powerful telescopes at these distances.

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