Moons of Uranus

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Uranus, the 7th planet from the sun has a total of 28 natural satellites. This is a complete list of natural satellites.

As with all lists, it will always remain incomplete. Please take some time to help complete the list. We will really appreciate your contribution!

Groups

Inner Moons

As of 2020, Uranus has 13 inner moons. All of their orbits lie inside Miranda's orbit and are near to the rings. All are relatively small except for the large Puck.

Large Moons

Uranus has five major moons: Miranda, Ariel, Umbriel, Titania, and Oberon. They range in diameter from 472 km for Miranda to 1578 km for Titania. All these moons are relatively dark objects and non-reflective.

Irregular Moons

As of 2005 Uranus is known to have nine irregular moons, which orbit it at a distance much greater than that of Oberon, the furthest of the large moons. All the irregular moons are probably captured objects that were trapped by Uranus soon after its formation. The diagram illustrates the orbits of those irregular moons discovered so far. The moons above the X axis are prograde, those beneath are retrograde. The radius of the Uranian Hill sphere is approximately 73 million km.

Uranus's irregular moons range in size from 120–200 km (Sycorax) to about 20 km (Trinculo). Unlike Jupiter's irregulars, Uranus's show no correlation of axis with inclination. Instead, the retrograde moons can be divided into two groups based on axis/orbital eccentricity. The inner group includes those satellites closer to Uranus (a < 0.15 r_H) and moderately eccentric (~0.2), namely Francisco, Caliban, Stephano, and Trinculo. The outer group (a > 0.15 r_H) includes satellites with high eccentricity (~0.5): Sycorax, Prospero, Setebos, and Ferdinand.

The intermediate inclinations 60° < i < 140° are devoid of known moons due to the Kozai instability. In this instability region, solar perturbations at apoapsis cause the moons to acquire large eccentricities that lead to collisions with inner satellites or ejection. The lifetime of moons in the instability region is from 10 million to a billion years.

Margaret is the only known irregular prograde moon of Uranus, and it currently has the most eccentric orbit of any moon in the Solar System, though Neptune's moon Nereid has a higher mean eccentricity. As of 2008, Margaret's eccentricity is 0.7979.

Spurious Moons

After Herschel discovered Titania and Oberon, he believed that he saw four other moons. However, those four other moons could not be confirmed. When other astronomers later looked at Uranus, they did not spot those four moons. Those four moons were probably just faint stars in the background. It is also possible that two of those four moons Herschel saw were Ariel and Umbriel.

Confirmed Moons

Key

Inner Moons	Major Moons	Other Irregular Retrograde Moons	Prograde Irregular Moon	Caliban Group
i	†	‡	±	♦

List

Numeral	Name	Diameter	Gravity	Escape Velocity	Orbital Period	Group Label	Year of Discovery
-	Uranus	50724 km	8.69 m/s²	21.3 km/s	30681 days (84 earth years)	-	1781
I	Ariel	1157.8±1.2 km	0.249 m/s²	0.537 km/s	2.52038 days	†	1851
II	Umbriel	1169.4±5.6 km	0.25 m/s²	0.54 km/s	4.14418 days	†	1851
III	Titania	1576.8±1.2 km	0.365 m/s²	0.759 km/s	8.70587 days	†	1781
IV	Oberon	1522.8±5.2 km	0.354 m/s²	0.734 km/s	3.4632 days	†	1781
V	Miranda	471.6 ± 1.4 km	0.077 m/s²	0.19 km/s	1.41348 days	†	1948
VI	Cordelia	40 ± 6 km	~0.0073 m/s²	0.017 km/s	0.33503 days	i	1986
VII	Ophelia	43 ± 8 km	~0.007 m/s²	0.018 km/s	0.37640 days	i	1986
VIII	Bianca	51 ± 4 km	~0.0086 m/s²	0.022 km/s	0.46357 days	i	1986
IX	Cressida	80 ± 4 km	~0.013 m/s²	0.034 km/s	0.46357 days	i	1986
X	Desdemona	64 ± 8 km	~0.011 m/s²	0.027 km/s	0.47365 days	i	1986
XI	Juliet	94 ± 8 km	~0.016 m/s²	0.04 km/s	0.49307 days	i	1986
XII	Portia	135 ± 8 km	~0.023 m/s²	0.058 km/s	0.51320 days	i	1986
XII	Rosalind	72 ± 12 km	~0.012 m/s²	0.031 km/s	0.55846 days	i	1986
XIV	Belinda	90 ± 16 km	~0.014 m/s²	~0.034 km/s	0.62353 days	i	1986
XV	Puck	162 ± 4 km	0.028 m/s²	0.069 km/s	0.76183 days	i	1985
XVI	Caliban	~42 km	?	?	579.73 days	♦	1997
XVII	Sycorax	~157 km	?	?	1288.38 days	‡	1997
XVIII	Prospero	~50 km	~0.0063 m/s²	~0.021 km/s	1978.37 days	‡	1999
XIX	Setebos	~48 km	~0.0063 m/s²	~0.0204 km/s	2225.08 days	‡	1999
XX	Stephano	~32 km	~0.0041 m/s²	~0.013 km/s	677.47 days	♦	1999
XXI	Trinculo	~18 km	~0.0021 m/s²	0.007 km/s	749.4 days	‡	2001
XXII	Francisco	~22 km	~0.0025 m/s²	0.0094 km/s	267.09 days	‡	2003
XXIII	Margaret	~20 km	~0.0023 m/s²	~0.0085 km/s	1661 days	±	2003
XXIV	Ferdinand	~12 km	?	?	2790.03 days	‡	2003
XXV	Perdita	30 ± 6 km	~0.0047 m/s²	~0.0011 km/s	0.638 days	i	1999
XXVI	Mab	~18 km	~0.0044 m/s²	~0.011 km/s	0.923 days	i	2003
XXVII	Cupid	~18 km	~0.0031 m/s²	~0.0076 km/s	0.618 days	i	2003
-	S/2023 U 1	~12 km	?	?	680.76 days	♦	2023

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