Astronomy Practice Exam

What is a gas giant?

1. A planet with a solid surface and an atmosphere

2. A planet primarily made up of gases

3. A planet with a very high density

4. A small rocky planet

The correct answer is: A planet primarily made up of gases

A gas giant is defined as a planet primarily made up of gases. These planets, like Jupiter and Saturn, have thick atmospheres composed mainly of hydrogen and helium, often with traces of other gases. Unlike terrestrial planets, gas giants do not have a well-defined solid surface; instead, they may have a core surrounded by a dense atmosphere that transitions from gaseous to liquid states under immense pressure deep within the planet. This characteristic composition and structure distinguish gas giants from other types of planets. Options that describe planets with solid surfaces, high density, or those that are small and rocky do not accurately represent the nature of gas giants.