Four Gas Giants

Jupiter, Saturn, Uranus and Neptune are less dense than the Earth or the other rocky planets, yet they have 10 times the mass of Earth!  Uranus and Neptune are called the "ice giants" because of their distance from the Sun and they are made up of different gases than Jupiter and Saturn.  They contain more ammonia, and methane gases. 

Within Jupiter and Saturn are layers of molecular hydrogen and liquid hydrogen.  Most scientists agree that Neptune and Uranus have rocky cores, but are covered in ice!

The cores of Jupiter and Saturn are under such massive pressure that they are really, really hot! The estimate is 20,000 degrees Kelvin.  The icy planets, Neptune and Uranus have cooler cores, and they don't have as much mass as the gas giants.  Their estimated core heat is only 5,000 degrees Kelvin.

All four of these outer giants have a ring system.  We are very familiar with Saturn's rings because we can see them so well.

Jupiter's rings are very faint, but they are there.  Meteors and meteorites kick up dust when they hit Jupiter's moons.  This creates a very faint ring as the dust, rocks and debris orbits Jupiter.

Astronomers have discovered other gas giants in our Solar System.  This type of planet is not rare, but very common.