Comets and stars are two different celestial objects, with distinct characteristics that set them apart.

A comet is a small, icy body that orbits the Sun. When a comet comes close to the Sun, the heat causes some of the ice to vaporize, creating a glowing coma (a bright, fuzzy halo) around the comet. The comet's tail, composed of gas and dust, is also created by the vaporization of ice as it is blown away from the coma by the solar wind.

On the other hand, a star is a massive, luminous object that is powered by nuclear fusion, which produces light and heat. Unlike comets, stars are not made of ice or dust, and they do not have a coma or a tail. Stars are typically much larger than comets and have a much longer lifespan.

The main differences between comets and stars can be summarized as follows:

1. Composition: Comets are made of ice and dust, while stars are made of gas, primarily hydrogen, and helium.

2. Size: Comets are relatively small, usually only a few kilometers in diameter, while stars can be massive, ranging in size from a few times the size of the Earth to hundreds of times larger than the Sun.

3. Luminosity: Comets are not luminous on their own and only become visible when they are close to the Sun, whereas stars are self-luminous and can be seen from great distances.

4. Lifespan: Comets have a relatively short lifespan, typically only surviving for a few passes around the Sun before they break apart or dissipate. In contrast, stars have much longer lifespans, with some living for billions of years.

In summary, comets and stars are two distinct celestial objects with different characteristics. Comets are small icy bodies that create a glowing coma and a tail when they come close to the Sun, while stars are massive, self-luminous objects that are powered by nuclear fusion.