Major moon in the context of Alan Stern

There are 29 known moons of the planet Uranus. The 27 with names are named after characters that appear in, or are mentioned in William Shakespeare's plays and Alexander Pope's poem The Rape of the Lock. Uranus's moons are divided into three groups: fourteen inner moons, five major moons, and ten irregular moons. The inner and major moons all have prograde orbits and are cumulatively classified as regular moons. In contrast, the orbits of the irregular moons are distant, highly inclined, and mostly retrograde.

The inner moons are small dark bodies that share common properties and origins with Uranus's rings. The five major moons are ellipsoidal, indicating that they reached hydrostatic equilibrium at some point in their past (and may still be in equilibrium), and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces. The largest of these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, about one-twentieth the mass of the Earth's Moon. The orbits of the regular moons are nearly coplanar with Uranus's equator, which is tilted 97.77° to its orbit. Uranus's irregular moons have elliptical and strongly inclined (mostly retrograde) orbits at large distances from the planet.

Oberon (/ˈoʊbərɒn/) is the outermost and second-largest major moon of the planet Uranus. It is the second-most massive of the Uranian moons, and the tenth-largest moon in the Solar System. Discovered by William Herschel in 1787, Oberon is named after the mythical king of the fairies who appears as a character in Shakespeare's A Midsummer Night's Dream. Its orbit lies partially outside Uranus's magnetosphere.

Oberon likely formed from the accretion disk that surrounded Uranus just after the planet's formation. The moon consists of approximately equal amounts of ice and rock, and is probably differentiated into a rocky core and an icy mantle. A layer of liquid water may be present at the boundary between the mantle and the core. The surface of Oberon, which is dark and slightly red in color, appears to have been primarily shaped by asteroid and comet impacts. It is covered by numerous impact craters reaching 210 km in diameter. Oberon possesses a system of chasmata (graben or scarps) formed during crustal extension as a result of the expansion of its interior during its early evolution.