Gas Giants: Facts About the Outer Planets

A gas giant is a large planet composed mostly of gases, such as hydrogen and helium, with a relatively small rocky core. The gas giants of our solar system are Jupiter, Saturn, Uranus and Neptune. 

These four large planets reside in the outer part of the solar system past the orbits of Mars and the asteroid belt. But the worlds are quite distinct from one another. Jupiter and Saturn are substantially larger than Uranus and Neptune, and each pair of planets (Jupiter and Saturn, vs. Uranus and Neptune) has a somewhat different composition.