Its called the 'Coma'. Its is both the dust that the solar wind blows off the comet as well as gases expelled as the comet heats up.
A coma
The center of a comet is called its nucleus.
The Coma is the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun.
The frozen portion of a comet consists mainly of ice, including water ice, carbon dioxide ice (dry ice), and various other frozen gases and compounds. This frozen portion makes up the nucleus of the comet, which is surrounded by a cloud of gas and dust when the comet is active.
The halo of light around a comet is called the coma. It is made up of gas and dust that are released from the comet as it approaches the sun and is illuminated by sunlight, creating a glowing cloud around the comet.
The part of a comet around the nucleus is called the coma. It is a dense cloud of gas and dust that forms around the nucleus as the comet approaches the Sun and starts to heat up, creating a glowing halo.
A hazy Cloud called coma sorrounds the head of a comet.
This is the coma, the portion of the comet that sublimates from the surface as it approaches the sun.
The "coma".
Particles around a comet usually include dust and gas that are released as the comet approaches the sun. These particles form a glowing cloud called a coma which envelops the nucleus of the comet. As the comet gets closer to the sun, the solar wind pushes on the particles in the coma, creating the tail that points away from the sun.
The bright glowing gases at the central part of a comet are called the coma. They are produced as the comet comes closer to the sun and the heat causes the ice and other volatile compounds on the comet's surface to sublimate, creating a cloud of gas and dust around the nucleus.
The hazy cloud surrounding the center of a comet is called the coma. It is formed as the comet approaches the Sun, causing volatile compounds to vaporize and create a fuzzy, expanding atmosphere around the nucleus.