Description: A gas giant is a giant planet mostly composed of hydrogen and helium which are gases in interstellar and interplanetary space, hence the name. However, most of the hydrogen and helium in gas giants is actually in a liquid state.

Gas giants are thought to have rocky cores which are surrounded by thick layers of hydrogen and helium. In the deepest parts of the planet these gases are compressed into liquid form with the deepest layers thought to contain an ocean of metallic hydrogen. In the outer layers the hydrogen and helium are in gas form. Other elements in the atmosphere can form clouds and rain. In the coolest gas giants the clouds in the upper layer can be made of water or ammonia vapor. In deeper, hotter layers of cooler gas giants and in the outer layers of hotter gas giants the clouds can be made of iron and minerals which are solid at room temperature.

The two largest planets in the Solar System, Jupiter and Saturn, are gas giants.

Related Terms:

• Giant Planet
• Jupiter
• Saturn

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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