What is the head of a comet usually containing a nucleus referred to as?

The head of a comet, which contains the nucleus, is referred to as the coma. The coma is the nebulous envelope surrounding the nucleus of a comet, formed when the comet approaches the Sun. As the comet gets closer to the Sun, the heat causes the nucleus, which is made up of ice, dust, and gas, to vaporize and release material, creating this cloud-like atmosphere. The coma can be quite extensive and is often visible from Earth, which gives comets their striking appearance.

In contrast, the tail of a comet refers to the stream of gas and dust particles that are pushed away from the comet's nucleus by the solar wind and radiation pressure, creating a distinct tail that points away from the Sun. The orbit denotes the curved path that the comet follows around the Sun, while the core typically refers to the central part of an object. Understanding the term "coma" helps distinguish the various structural components of a comet and their interactions with solar forces.