Right now, I'm watching a great show on the National Geographic Channel about comets. The show is titled: Naked Science Comets
This special is describing how a large body of comets exists outside our solar system. The comets themselves are left over debris from the formation of all of the planets. The comets are black as coal and only show-up and develop their tails because of the heat from our sun. Apparently, the tails are simply gases and debris that breaks away from the rock as its heated from the sun. The tails can be a few feet to a million miles in length.
What do you guys know about comets?

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