Gas giant

A gas giant is a type of planet comprised primarily of gas, generally with a small rocky core located deep within the layers of gas at the center of the planet.

The most common gas giants are made primarily of helium and hydrogen, although other elements are common. It is possible that a gas giant can have an oxygen-rich layer, but is generally rare. The most famous gas giant to have a habitable layer is Khettal, the capital world of Pollux.