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.
head
nucleus and coma
A comet
The "coma".
This is the coma, the portion of the comet that sublimates from the surface as it approaches the sun.
A hazy Cloud called coma sorrounds the head of a comet.
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".