Worlds of David Darling
Encyclopedia of Science
   
Home > Encyclopedia of Science

moons of Uranus





Uranus moons
Uranus has 27 known moons, placing it third, by this reckoning, behind Jupiter (63) and Saturn (33). The first two were discovered by William Herschel in 1787, and named, by his son, after characters from Shakespeare’s A Midsummer Nights Dream, Titania and Oberon. Two more moons were found by William Lassell in 1851 and named Ariel and Umbriel; G. Kuiper discovered Miranda in 1948. All the moons of Uranus are named after characters from Shakespeare or Alexander Pope. Voyager 2’s flyby in January 1986 led to the discovery of another 10. Twelve additional moons have since been discovered by telescope.

In an unusual move, in late 2001, the International Astronomical Union stripped the title of “moon” from a small body seen in images taken by Voyager and previously reported to be orbiting Uranus. The IAU concluded that there wasn't yet enough data to confirm that the object, designated S/1986 U10, is a satellite. It appeared to be in nearly the same orbit as another moon, Belinda, about 75,000 km from Uranus, and, based on its brightness in the Voyager images, to have a diameter of about 40 km. S/1986 U 10 has not been seen since the Voyager 2 discovery, despite observing efforts that have discovered several other small moons orbiting the planet.

Two of the most recently discovered satellites, Cupid (S/2003 U1) and Mab (S/2003 U2), belong to the inner collection of satellites, each orbiting Uranus in less than a day. Indeed, it's hard to understand how the inner swarm of 13 Uranian moons, which are so close together that they must be gravitationally unstable, can coexist. All the moons from S2001/U3 out move in retrograde orbits. Click on each of the satellite names that appear in orange in the table below for further information.


moon semimajor
axis (km)
orbital
period (days)
orbital
eccentricity
orbital
inclination (o)
diameter
(km)
Cordelia 49,750 0.335 0.0003 0.085 50 × 36
Ophelia 53,760 0.376 0.0099 0.104 54 × 38
Bianca 59,170 0.435 0.0009 0.193 64 × 46
Cressida 61,770 0.464 0.0004 0.006 92 × 74
Desdemona 62,660 0.474 0.0001 0.113 90 × 54
Juliet 64,360 0.493 0.0007 0.065 150 × 74
Portia 66,100 0.513 0.0001 0.060 156 × 126
Rosalind 69,930 0.558 0.0001 0.279 72 × 72
Cupid 74,800 0.618 0.0013 0.1? ~18
Belinda 75,260 0.624 0.0001 0.031 81 ± 16
Perdita 76,420 0.638 0.0012 0.0 30 × 30
Puck 86,000 0.762 0.0001 0.319 162 ± 4
Mab 97,730 0.923 0.0025 0.134 ~25
Miranda 129,390 1.413 0.0013 4.232 472
Ariel 191,020 2.520 0.0012 0.260 1,158
Umbriel 266,300 4.144 0.0039 0.205 1,169
Titania 435,910 8.706 0.0011 0.340 1,578
Oberon 583,520 13.46 0.0014 0.058 1,523
Francisco 4,275,900 267.12 (r) 0.1369 147.460 ~22
Caliban 7,164,900 579.39 (r) 0.0790 139.885 ~72
Stephano 7,952,200 677.48 (r) 0.1444 141.874 ~32
Trinculo 8,501,300 748.83 (r) 0.2177 166.25 ~18
Sycorax 12,189,100 1285.62 (r) 0.5137 152.447 ~150
Margaret 14,420,400 1654.32 (r) 0.7979 51.456 ~20
Prospero 16,162,200 1962.95 (r) 0.3296 146.17 ~25
Setebos 17,419,300 2196.35 (r) 0.5722 145.884 ~24
Ferdinand 20,507,100 2805.51 (r) 0.4312 167.346 ~20




Features in the Uranus system. Credit: NASA, ESA, and A. Feild (STScI)
Features in the Uranus system.
Credit: NASA, ESA, and A. Feild (STScI)



Archived news

Moongazing reveals the chaotic world of Uranus (Dec 28, 2005)


Related category

   • PLANETS AND MOONS