出典:Wikipedia
出典:『Wikipedia』 (2011/06/05 17:44 UTC 版)
In astronomy, a coma (from the Greek κόμη, "hair") 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.