Out past Neptune are vast reservoirs of icy bodies that can become comets if they get poked into the inner solar system. The Kuiper Belt is a donut-shaped region beyond the planets that is aligned with the plane of the solar system. The Scattered Disk is an eccentric region, and the source of short-period comets. The Oort Cloud, which surrounds the solar system out to great distances, is the source of long-period comets.
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