Uranus

For thousands of years mankind believed that there were only five planets in the solar system. But an astronomer called William Herschel discovered a new planet in 1781. Uranus orbits the Sun more than twice as far as Saturn. Uranus takes 84 Earth years to complete a single revolution around the Sun. Uranus is a gaseous planet like Saturn and Jupiter, with a distinct blue-green appearence, probably because of the concentration of methane in its upper atmosphere. Uranus has a core composed of silicate rock and metals, with a diameter of roughly 51,800 kilometers. It's core is covered by frozen methane ammonia and water ice 9600 kilometers deep. The most abundant elements in Uranus' atmosphere are hydrogen and helium. Its atmosphere also contains methane acetylane and other hydrocarbons.

Uranus has an axial inclination of 98 degrees, which was discovered in 1829. Uranus also has a ring system which was discovered in 1977. People thought Uranus had only nine rings, but when Voyager two passed Uranus two more were identified. Uranus' ring system probably did not form at the same time as the planet.

The widest ring prior to Voyager 2 visiting Uranus was the outermost ring, Epsilon, which measured from 22 to 96 kilometers. In 1986 Voyager 2 identified a new innermost ring called 1986UR2, which is 2500 kilometers wide. The narrowest complete rings are less than a kilometer wide.