Moons of Uranus
Uranus, the seventh planet of the Solar System, has 27 known moons, all of which are named after characters from the works of William Shakespeare and Alexander Pope. Uranus's moons are divided into three groups: thirteen inner moons, five major moons, and nine irregular moons. The inner moons are small dark bodies that share common properties and origins with Uranus's rings. The five major moons are massive enough to have reached hydrostatic 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, and about one-twentieth the mass 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.
Naming of moons
In 1847 the seven then known moons of Saturn were named by John Herschel. Herschel named Saturn's two innermost moons (Mimas and Enceladus) after the mythological Greek Giants, and the outer five after the Titans (Titan, Iapetus) and Titanesses (Tethys, Dione, Rhea) of the same mythology. Until then, Titan was known as the "Huygenian (or Huyghenian) satellite of Saturn" and the other moons had Roman numeral designations in order of their distance from Saturn. Subsequent discoverers of Saturnian moons followed Herschel's scheme: Hyperion was discovered soon after in 1848, and the ninth moon, Phoebe, was named by its discoverer in 1899 soon after its discovery; they were named for a Titan and a Titaness respectively. The name of Janus was suggested by its discoverer, Audouin Dollfus.