What are celestial objects composed of mixtures of dust and gas called?

The term used to describe celestial objects composed of mixtures of dust and gas is specifically known for comets. Comets are composed primarily of water ice, frozen gases, dust, and rocky materials. When they come close to the Sun, the heat causes the ice to vaporize, releasing gas and dust in a glowing tail that is characteristic of these objects. This composition is what differentiates comets from other celestial bodies, such as asteroids, which are primarily made of rock and metal, or planets and stars, which have more distinct formation and structural differences. The presence of ices and the ability to form a coma and a tail when near the Sun are defining features of comets.