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Uranus Menu  

Moons of Uranus

Uranus has at least 27 moons known to orbit it. Its largest moons are Titania, Oberon, Umbriel, Ariel and Miranda. Titania and Oberon were discovered by William Herschel in 1787. Herschel was the astronomer who discovered Uranus itself six years earlier. Umbriel and Ariel were discovered by William Lassell in 1851, and Miranda was discovered by Gerard Kuiper in 1948. These five moons are all large enough to be spherical in shape.

In 1986, the spacecraft Voyager 2 reached Uranus and discovered ten small inner moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda and Puck. A moon called Perdita was also imaged by Voyager 2, but it wasn't until 1999 that astronomers realised this. Since Voyager 2's visit, several even more moons have been spotted by eagle-eyed astronomers using powerful modern telescopes. These are Cupid, Mab, Francisco, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos and Ferdinand. Most of these are very distant outer moons.

Unlike other moons in the Solar System which are named after mythological figures, the moons of Uranus get their names from characters in works of literature written by William Shakespeare and Alexander Pope. There's even a moon called Margaret!

Not just your regular moons

Like all of the large outer planets, Uranus has a bunch of regular inner moons, a bundle of regular major moons and a collection of outer irregular moons. Regular moons are those that formed in an orbit of Uranus from materials spinning and swirling around it, irregular ones are those that Uranus has captured.

The regular inner moons orbit fairly closely to the planet and its rings, in the same direction that the planet rotates (known as prograde) and roughly on a flat plane around the planet's equator.

Major moons are the planet's largest moons. Like the inner moons, they travel in a prograde direction and orbit around Uranus' equatorial plane. Uranus orbits on its side which means that its inner moons and major moons appear to go under and over it rather than around it.

Uranus' irregular moons orbit at great distances from the planet, in orbits which can be highly eccentric (oval-shaped) and aren't on the same plane as the planet's equator. This type of orbit is called an inclined orbit. All but one of Uranus' irregular moons travel in the opposite direction (retrograde) to the rotation of the planet.

Below is a list of the moons of Uranus. They are put into colour-coded groups because it makes the page look more attractive. Oh, and because it might be useful to have them in groups too.


Groups of Uranus' Moons

Shepherd Moons (Inner Group)
Two regular moons, Cordelia and Ophelia, which orbit on either side of Uranus' narrow ε ring (ε is the Greek equivalent of letter "e"). Their orbit appears to hold the ring together and prevent it from breaking apart.
Portia Group (Inner Group)
Regular moons with shared orbital characteristics. Little is known about them other than the fact that their close orbits constantly disturb each other leading to the possibility of them colliding with each other, breaking up or crashing into Uranus at some point in their futures.
Other Inner Group Moons
A couple of other regular moons which keep themselves out of the way of the Portia moons but share a lot of other similarities.
Major Moons
Uranus' largest moons, all spherical in shape and thought to have formed from a disk of materials scattered around Uranus after its formation.
Irregular Retrograde Moons (Outer Group)
Relatively small moons that orbit at distances between 4 million to 24 million kilometres from Uranus in inclined orbits between 141 to 170 degrees. They travel in an opposite direction to the rotation of Uranus and are probably objects that have been captured by Uranus.
Irregular Prograde Moons (Outer Group)
One moon, Margaret, which orbits at a distance of 14 million kilometres in an inclined orbit of 57 degrees and travels in the same direction of Uranus' rotation.

List of Uranus' Moons

Name of Moon Diameter Orbital Distance Length of Orbit Discovered Discoverer Group
Cordelia 40 km
25 miles
49,800 km
30,946 miles
8 hours 1986 Richard J. Terrile Shepherd
Ophelia 43 km
27 miles
53,800 km
33,431 miles
9 hours 1986 Richard J. Terrile Shepherd
Bianca 54 km
34 miles
59,200 km
36,787 miles
10 hours 1986 Bradford A. Smith Portia
Cressida 82 km
51 miles
61,800 km
38,403 miles
11 hours 1986 Stephen P. Synott Portia
Desdemona 70 km
44 miles
62,700 km
38,962 miles
11 hours 1986 Stephen P. Synott Portia
Juliet 106 km
66 miles
64,400 km
40,018 miles
12 hours 1986 Stephen P. Synott Portia
Portia 140 km
87 miles
66,100 km
41,075 miles
12 hours 1986 Stephen P. Synott Portia
Rosalind 72 km
45 miles
69,900 km
43,436 miles
13 hours 1986 Stephen P. Synott Portia
Cupid 18 km
11 miles
74,390 km
46,226 miles
15 hours 2003 Mark Robert Showalter, Jack Jonathan Lissauer Portia
Belinda 90 km
56 miles
75,300 km
46,791 miles
15 hours 1986 Stephen P. Synott Portia
Perdita 26 km
16 miles
76,420 km
47,487 miles
15 hours 1999 Erich Karkoschka Portia
Puck 162 km
101 miles
86,000 km
53,440 miles
18 hours 1985 Stephen P. Synott Inner
Mab 24 km
15 miles
97,740 km
60,736 miles
22 hours 2003 Mark Robert Showalter, Jack Jonathan Lissauer Inner
Miranda 480 km
298 miles
129,900 km
80,720 miles
34 hours 1948 Gerard Kuiper Major
Ariel 1,162 km
722 miles
190,900 km
118,625 miles
60 hours 1851 William Lassell Major
Umbriel 1,169 km
726 miles
266,000 km
165,292 miles
99 hours 1851 William Lassell Major
Titania 1,578 km
981 miles
436,300 km
271,117 miles
9 days 1787 William Herschel Major
Oberon 1,523 km
946 miles
583,500 km
362,587 miles
13 days 1787 William Herschel Major
Francisco 22 km
14 miles
4,276,000 km
2,657,106 miles
267 days 2003 Matthew J. Holman, Brett J. Gladman and teams Retrograde
Caliban 72 km
45 miles
7,231,000 km
4,493,343 miles
579 days 1997 Brett J. Gladman, J. J. Kavelaars, Phillip D. Nicholson, Joseph A. Burns Retrograde
Stephano 32 km
20 miles
8,004,000 km
4,973,686 miles
676 days 1999 Brett J. Gladman, J. J. Kavelaars, Matthew J. Holman, Jean-Mark Petit, Hans Scholl Retrograde
Trinculo 18 km
11 miles
8,504,000 km
5,284,386 miles
758 days 2001 Matthew J. Holman and team Retrograde
Sycorax 150 km
93 miles
12,179,000 km
7,568,031 miles
1283 days 1997 Brett J. Gladman, J. J. Kavelaars, Phillip D. Nicholson, Joseph A. Burns Retrograde
Margaret 20 km
12 miles
14,345,000 km
8,913,983 miles
1695 days 2003 Scott S. Sheppard, David C. Jewitt Prograde
Prospero 50 km
31 miles
16,256,000 km
10,101,478 miles
1977 days 1999 Brett J. Gladman, J. J. Kavelaars, Matthew J. Holman, Jean-Mark Petit, Hans Scholl Retrograde
Setebos 48 km
30 miles
17,418,000 km
10,823,545 miles
2235 days 1999 Brett J. Gladman, J. J. Kavelaars, Matthew J. Holman, Jean-Mark Petit, Hans Scholl Retrograde
Ferdinand 20 km
12 miles
20,901,000 km
12,987,881 miles
2823 days 2003 Matthew J. Holman and team Retrograde
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