Comet

A comet is a body of ice, dust, and rock that grows a glowing atmosphere and tail as it nears the Sun. Heating turns its ices directly to gas, releasing dust and forming a coma around the nucleus along with tails that always stream away from the Sun. Short-period comets come mostly from the Kuiper Belt, while long-period ones fall in from the distant Oort Cloud. Because their material has stayed frozen since the solar system formed, comets preserve a record of its original chemistry.

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