The layer of gases that covers a planet, star, or moon is called an atmosphere.

Here's a breakdown:

* Planets: Most planets in our solar system have atmospheres. They can vary greatly in composition and density, from the thick, mostly carbon dioxide atmosphere of Venus to the thin, nitrogen-oxygen atmosphere of Earth.

* Stars: Stars are essentially giant balls of hot gas, so they technically have an atmosphere. However, the term "atmosphere" is rarely used for stars. Instead, we talk about their photosphere, which is the visible surface layer of the star.

* Moons: Some moons, like Titan (Saturn's largest moon) and Europa (Jupiter's moon) have thin atmospheres. However, many moons have no significant atmosphere at all.

Let me know if you have any other questions!