What is the name of a celestial body that orbits a planet?

A celestial body that orbits a planet is called a moon. Moons are natural satellites that can vary in size and composition, and they can be found orbiting planets in our solar system as well as those in other star systems. For example, Earth has one moon, while Saturn has numerous moons, including Titan, which is larger than the planet Mercury.

The other options refer to different types of celestial objects. A star is a massive celestial body that generates light and heat through nuclear fusion, like our Sun. A comet is composed mostly of ice and dust, and it typically has a highly elliptical orbit that takes it close to the Sun, where it displays a coma and sometimes a tail. A galaxy is an enormous collection of stars, gas, dust, and dark matter bound together by gravity, containing millions or even billions of stars, along with their respective planetary systems. Thus, the distinct definition of a moon makes it the correct term for a body that orbits a planet.