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Uranus' moons are named after Shakespearian characters.
Uranus has 27 known moons. The first two moons (Titania and Oberon) were discovered by William Herschel on March 13, 1787. Two more Uranus moons (Ariel and Umbriel) were discovered by William Lassell in 1851. In 1852, Herschel's son John Herschel gave the four then-known Uranus moons their names. In 1948 Gerard Kuiper discovered the moon Miranda.
The flyby of the Voyager 2 space probe in January 1986 led to the discovery of a further 10 inner moons, and another satellite Perdita was later found after studying old Voyager photographs. Two more small inner moons were discovered by astronomers using the Hubble Space Telescope. Until 1997, Uranus was the only giant planet with no known irregular satellites. Since then, nine distant irregular moons have been identified using ground-based telescopes.
The region between the main rings and Miranda appears to be very crowded. The small moons there are constantly perturbed by each other. The system is chaotic and apparently unstable, and simulations show that the moons may perturb each other into crossing orbits which may result in collisions between the moons.
Unlike most planetary moons, which are named from antiquity, all the moons of Uranus are named after characters from the works of Shakespeare and Alexander Pope.
The natural satellites of Uranus.
The Uranian moons are listed here by orbital period, from shortest to longest. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in light blue. Irregular (captured) moons with prograde orbits are shown in light grey, those with retrograde orbits in dark grey.
Sources: NASA/NSSDC, University of Hawaii and Natural Satellites Ephemeris Service (for the outer satellites). These sources give no information on the masses for the small satellites.
Irregular satellites or moons of Uranus.
The diagram illustrates the orbits of the Irregular satellites of Uranus discovered so far. The eccentricity of the orbits is represented by the yellow segments (extending from the pericentre to the apocentre) with the inclination represented on Y axis. The satellites above the axis are prograde, the satellites beneath are retrograde. The X axis is labelled in Gm (million km) and the fraction of the Hill sphere's (gravitational influence) radius (approximately 70 million km for Uranus).
Unlike for Jupiter's irregulars, no correlation axis versus inclination can be found among the known population. Instead, the retrograde moons can be divided into two groups based on axis/eccentricity. The inner group includes satellites closer to Uranus (a < 0.15 rH) and moderately eccentric (~0.2), namely: Francisco, Caliban, Stephano and Trinculo. The outer group (a > 0.15 rH) includes satellites with high eccentricity (~0.5): Sycorax, Prospero, Setebos and Ferdinand.
Naming notes for Uranus moons.
Some asteroids share the same names as moons of Uranus: 171 Ophelia, 218 Bianca, 593 Titania, 666 Desdemona, 763 Cupido and 2758 Cordelia. See also Name conflicts of solar system bodies.
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