Oberon is one of Uranus’s moons. It was discovered in 1787 by the German-born British astronomer William Herschel.
Mass: 3.01 x 1021 kg
Composition: Water-ice, rock and organic compounds
Orbit: 5.83 x 105 m from Uranus
Oberon is the outermost of Uranus’ five major moons and the ninth-largest moon in the Solar System. Uranus has five major satellites and 22 minor satellites, according to NASA. The major five moons were discovered from direct observations on Earth, 11 others were discovered by the Voyager 2 spacecraft mission and the remainder by sensitive charge-coupled-device (CCD) detectors from Earth.
All of Uranus’s moons were give the names of characters from the works of William Shakespeare and Alexander Pope. Oberon got its name from one of the characters in Shakespeare’s “A Midsummer Night’s Dream”. John, the son of William Herschel, suggested these names in 1852. William Lassell, a British astronomer who discovered two other moons of Uranus and called them Umbriel and Ariel, had requested this of John Herschel.
The composition of Oberon seems to be equal proportions of water-ice and non-ice components. As in Titania, these other components consist of rock and organic compounds such as clathrate hydrates and methane. Clathrate hydrates are molecules of methane that are trapped within water molecules and are also called methane hydrates or gas hydrates. Oberon may have a core of rock enclosed by an ice mantle. Like Titania, Oberon might have a level of liquid ocean at the boundary between core and mantle if the moon’s water-ice contains sufficient ammonia or another compound that acts as an antifreeze.
Oberon is the second-darkest large moon of Uranus after Ariel and has the reddest surface of the major Uranus moons. The surface is marked with craters and chasmata. The latter are canyons and lineaments that resemble rift valleys and escarpments. The older chasmata are between 70 and 80 km wide, while younger structures are about 20 km wide. These were caused by extensional forces in the surface layer of the moon as well as heavy bombardment by meteorites. Oberon’s largest single crater, Hamlet, is 206 km in diameter. The most prominent canyon is Mommur Chasma, named after the enchanted forest ruled by Oberon.
Oberon orbits synchronously around Uranus over an orbital period of 13.5 Earth days. This coincides with the rotational period of the moon on its own axis. The same hemisphere of Titania always faces Uranus. Along with Uranus and its other satellites, Oberon takes 84 Earth years to orbit the sun.
The Voyager 2 spacecraft mission in 1986 photographed Uranus and its moons. Its closest approach was at a distance of 470,600 km and the photographs had a resolution of 6 km. There have been no other missions to Uranus and its moons since then.