Gas giant

A gas giant is a giant planet that has a solid core, but a very thick atmosphere. This means that most of the planet is made up of gas. These planets are very large. The main components are hydrogen and helium.

The inside of Jupiter. The solid core is shown in brown

In our Solar System, there are formally four gas giants: Jupiter and Saturn are mainly composed of hydrogen, helium, and neon, however Uranus, and Neptune are formally or not included here, they are also called ice giants of formal form.

Jupiter and Saturn are similar because they are made up of mostly hydrogen and helium. They both contain massive, rocky cores that are bigger than Earth. Neptune and Uranus are similar because they are mainly made up of ice and rock (a mixture of one or several minerals).

Gas giants have also been found around other stars than the sun. Most of those giant extrasolar planets are "hot giants" orbiting close to their star.