A Gas Giant is a huge planet whose main composition is Hydrogen and Helium, with small amounts of rocky material at their cores. In our Solar System, there are four of them, also known as Jovian or Outer planets: Jupiter, Saturn, Uranus and Neptune. The term was coined in 1952 by american science fiction writer James Blish. The term may be a misnomer, because below the surface, due to extreme pressure and temperature, the planet consist mainly of liquid and solid phases of Hydrogen and Helium.
Characteristics
Ring System
Ring system of Saturn
A ring system around a planet is a disk (or disks) made up of ice and dust. The largest and most know ring
Jupiter with its moons
system of our Solar System is that of Saturn. The other 3 Outer Planets also have rings, but smaller ones.
Moons
The Gas Giants share a common factor: all of them have a lot of moons. Jupiter has 79 moons, the four biggest are Io, Ganymede, Europa and Callisto. Saturn has 62, including the enormous Titan, which is bigger than the planet Mercury. Uranus has 27 and Neptune has 14.