A comet's gaseous envelope (which creates the tail) is called what?

The gaseous envelope that creates the tail of a comet is called the coma. The coma is formed as the comet approaches the sun and the heat causes the icy nucleus of the comet to vaporize, releasing gas and dust particles. The coma is a glowing, cloud-like structure that surrounds the nucleus and can extend for thousands of kilometers. As the sun's radiation pushes against the coma, it creates a glowing tail that always points away from the sun due to solar wind. The coma plays a crucial role in the visual appearance of comets and provides valuable information about their composition and activity.