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.
Jumping-Jupiter scenario
The encounters between planets also perturb the orbits of the moons of the other outer planets. Saturn's moon Iapetus could have been excited to its current inclination, if the ice giant's closest approach was out of the plane of Saturn's equator. If Saturn acquired its tilt before the encounters, Iapetus's inclination could also be excited due to multiple changes of its semi-major axis, because the inclination of Saturn's Laplace plane would vary with the distance from Saturn. In simulations, Iapetus was excited to its current inclination in five of ten of the jumping-Jupiter models tested, though three left it with excessive eccentricity. The preservation of Oberon's small inclination favors the 5-planet models, with only a few encounters between Uranus and an ice giant, over 4-planet models in which Uranus encounters Jupiter and Saturn. The low inclination of Uranus's moon Oberon, 0.1°, was preserved in nine out of ten of five planet models, while its preservation was found to be unlikely in four planet models. The encounters between planets may have also be responsible for the absence of regular satellites of Uranus beyond the orbit of Oberon.