The gas giants are Jupiter, Saturn, Uranus and Neptune. Jupiter and Saturn are made of Hydrogen and Helium. There symbols are H and He. Jupiter is a failed star but it is not glowing. Its fast rotation is warming it up. Saturn has the second fastest rotation. Jupiter's rotation is 9 hours and Saturn's is 10. Uranus' and Neptune's are also quick. Before I found out they were quick, I thought they were 20 hours.