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nucleus (cometary)

nucleus of a comet
Artist's impression of a comet's nucleus
A cometary nucleus is the central and relatively small part of a comet. It is often described as a "dirty snowball" since it is made up of about 75 percent ices (including frozen water, ammonia and carbon dioxide) and about 25 percent dust and rock.

Related entry

   • Halley's Comet

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