Its the nebulous shock around the nucleus of the comet. Basically its the head of the comet.
The Coma is the fuzzy outer layer of a comet.
The "coma".
Halley's comet coma is 100,000 miles vs 15 miles.
This is the coma, the portion of the comet that sublimates from the surface as it approaches the sun.
nucleus and coma
The "coma".
A comet
head
The tail of a comet, also known as its coma, grows as the comet gets close to the sun because of increases in temperature and force exerted by the solar wind. Since a comet's coma is usually composed of dust and vapor, the solar wind causes it to stream out away from the sun.
Comet Tempel 1, as viewed by the Stardust-NEXT mission Credit. The total brightness of coma and nucleus is 10 units, the coma is 9 units.
A comet forms a so-called coma when it passes near the Sun. A comet undergoes sublimation when it warms up therefore producing a fuzzy like appearance. The term coma comes from the Greek word "kome" which means "hair".
A hazy Cloud called coma sorrounds the head of a comet.