Coma
A coma is the fuzzy cloud of gas and dust that surrounds a comet's nucleus as it nears the Sun.
A coma is the glowing cloud around the solid nucleus of a comet. When a comet gets close enough to the Sun, its ices, mainly water, carbon dioxide and carbon monoxide, warm up and turn directly into gas. The gas streams away, carrying dust with it, and forms a hazy cloud that can be hundreds of thousands of kilometres across, larger than the Sun in some cases.
The coma shines partly by reflecting sunlight off dust and partly because gas molecules glow when struck by ultraviolet light. Some comets have a green coma, caused by molecules of carbon, called C2, that glow green before being broken apart by sunlight.
The coma is where comet dust begins its journey. Some of it is swept back into tails, and some spreads along the comet's orbit, forming a meteoroid stream. When Earth passes through the stream, we see a meteor shower.
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Level: Beginner Ages 7 and up