The
coma is the nebulous envelope around the
nucleus of a
comet. It is formed when the comet passes close to the
Sun on its highly
elliptical orbit; as the comet warms, parts of it
sublimate. This gives a comet a "fuzzy" appearance when viewed in
telescopes and distinguishes it from
stars. The word
coma comes from the Greek "kome" (κόμη), which means "hair" and is the origin of the word
comet itself.