What is the term for the temporary, vast, hazy atmosphere that forms around a comet's nucleus when it becomes active?

Answer

Coma

The escaping gas and dust driven off the nucleus form an expansive, temporary atmosphere surrounding the solid core, which is termed the coma.

What is the term for the temporary, vast, hazy atmosphere that forms around a comet's nucleus when it becomes active?
Spaceastronomycometcelestial objectspace object