Uranus was discovered by Sir William Herschel in 1781. The planet is actually a gas giant, composed of methane, helium and hydrogen. Its temperature hovers around -355 degrees Fahrenheit. Some scientists believe that despite the cold surface temperatures, a core about fifteen times the size of earth has a temperature of approximately 12,000 degrees Fahrenheit. It possesses at least five major moons, ten minor moons, and thirteen rings. Idea: Encourage children to try to develop some kind of transport that could land on the gas giant. They could learn more at: Uranus.