Moons of Uranus

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A near-infrared image of the six largest moons and eight inner moons of Uranus as captured by the James Webb Space Telescope on 4 September 2023 Annotated Moons of Uranus.png
A near-infrared image of the six largest moons and eight inner moons of Uranus as captured by the James Webb Space Telescope on 4 September 2023

Uranus, the seventh planet of the Solar System, has 28 confirmed moons. The 27 with names are named after characters that appear in, or are mentioned in, William Shakespeare's plays and Alexander Pope's poem The Rape of the Lock . [1] Uranus's moons are divided into three groups: thirteen inner moons, five major moons, and ten irregular moons. The inner and major moons all have prograde orbits and are cumulatively classified as regular moons. In contrast, the orbits of the irregular moons are distant, highly inclined, and mostly retrograde.

Contents

The inner moons are small dark bodies that share common properties and origins with Uranus's rings. The five major moons are ellipsoidal, indicating that they reached hydrostatic equilibrium at some point in their past (and may still be in equilibrium), and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces. [2] The largest of these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, about one-twentieth the mass of 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. [3]

William Herschel discovered the first two moons, Titania and Oberon, in 1787. The other three ellipsoidal moons were discovered in 1851 by William Lassell (Ariel and Umbriel) and in 1948 by Gerard Kuiper (Miranda). [1] These five may be in hydrostatic equilibrium. The remaining moons were discovered after 1985, either during the Voyager 2 flyby mission or with the aid of advanced Earth-based telescopes. [2] [3]

Discovery

The first two moons to be discovered were Titania and Oberon, which were spotted by Sir William Herschel on January 11, 1787, six years after he had discovered the planet itself. Later, Herschel thought he had discovered up to six moons (see below) and perhaps even a ring. For nearly 50 years, Herschel's instrument was the only one with which the moons had been seen. [4] In the 1840s, better instruments and a more favorable position of Uranus in the sky led to sporadic indications of satellites additional to Titania and Oberon. Eventually, the next two moons, Ariel and Umbriel, were discovered by William Lassell in 1851. [5] The Roman numbering scheme of Uranus's moons was in a state of flux for a considerable time, and publications hesitated between Herschel's designations (where Titania and Oberon are Uranus II and IV) and William Lassell's (where they are sometimes I and II). [6] With the confirmation of Ariel and Umbriel, Lassell numbered the moons I through IV from Uranus outward, and this finally stuck. [7] In 1852, Herschel's son John Herschel gave the four then-known moons their names. [8]

No other discoveries were made for almost another century. In 1948, Gerard Kuiper at the McDonald Observatory discovered the smallest and the last of the five large, spherical moons, Miranda. [8] [9] Decades later, the flyby of the Voyager 2 space probe in January 1986 led to the discovery of ten further inner moons. [2] Another satellite, Perdita, was discovered in 1999 [10] by Erich Karkoschka after studying old Voyager photographs. [11]

Uranus was the last giant planet without any known irregular moons until 1997, when astronomers using ground-based telescopes discovered Sycorax and Caliban. From 1999 to 2003, astronomers continued searching for irregular moons of Uranus using more powerful ground-based telescopes, resulting in the discovery of seven more Uranian irregular moons. [3] In addition, two small inner moons, Cupid and Mab, were discovered using the Hubble Space Telescope in 2003. [12] No other discoveries were made until 2021 and 2023, when Scott Sheppard and colleagues discovered one more irregular moon of Uranus (and five more candidates waiting to be announced) using the Subaru Telescope at Mauna Kea, Hawaii. [13] [14] [15]

Spurious moons

After Herschel discovered Titania and Oberon on 11 January 1787, he subsequently believed that he had observed four other moons: two on 18 January and 9 February 1790, and two more on 28 February and 26 March 1794. It was thus believed for many decades thereafter that Uranus had a system of six satellites, though the four latter moons were never confirmed by any other astronomer. Lassell's observations of 1851, in which he discovered Ariel and Umbriel, however, failed to support Herschel's observations; Ariel and Umbriel, which Herschel certainly ought to have seen if he had seen any satellites besides Titania and Oberon, did not correspond to any of Herschel's four additional satellites in orbital characteristics. Herschel's four spurious satellites were thought to have sidereal periods of 5.89 days (interior to Titania), 10.96 days (between Titania and Oberon), 38.08 days, and 107.69 days (exterior to Oberon). [16] It was therefore concluded that Herschel's four satellites were spurious, probably arising from the misidentification of faint stars in the vicinity of Uranus as satellites, and the credit for the discovery of Ariel and Umbriel was given to Lassell. [17]

Discovery of outer planet moons

   Moons of Jupiter
   Moons of Saturn
   Moons of Uranus

Names

Although the first two Uranian moons were discovered in 1787, they were not named until 1852, a year after two more moons had been discovered. The responsibility for naming was taken by John Herschel, son of the discoverer of Uranus. Herschel, instead of assigning names from Greek mythology, named the moons after magical spirits in English literature: the fairies Oberon and Titania from William Shakespeare's A Midsummer Night's Dream , and the sylph Ariel and gnome Umbriel from Alexander Pope's The Rape of the Lock (Ariel is also a sprite in Shakespeare's The Tempest ). [18] It is uncertain if John Herschel was the originator of the names, or if it was instead William Lassell (who discovered Ariel and Umbriel) who chose the names and asked Herschel for permission. [19]

Subsequent names, rather than continuing the airy spirits theme (only Puck and Mab continued the trend), have focused on Herschel's source material. In 1949, the fifth moon, Miranda, was named by its discoverer Gerard Kuiper after a thoroughly mortal character in Shakespeare's The Tempest . [8] The current IAU practice is to name moons after characters from Shakespeare's plays and The Rape of the Lock (although at present only Ariel, Umbriel, and Belinda have names drawn from the latter; all the rest are from Shakespeare). The outer retrograde moons are all named after characters from one play, The Tempest; the sole known outer prograde moon, Margaret, is named from Much Ado About Nothing . [19]

Some asteroids, also named after the same Shakespearean characters, share names with moons of Uranus: 171 Ophelia, 218 Bianca, 593 Titania, 666 Desdemona, 763 Cupido, and 2758 Cordelia.

Characteristics and groups

The Uranian satellite system is the least massive among those of the giant planets. Indeed, the combined mass of the five major satellites is less than half that of Triton (the seventh-largest moon in the Solar System) alone. [a] The largest of the satellites, Titania, has a radius of 788.9 km, [21] or less than half that of the Moon, but slightly more than that of Rhea, the second-largest moon of Saturn, making Titania the eighth-largest moon in the Solar System. Uranus is about 10,000 times more massive than its moons. [b]

Inner moons

Schematic of the Uranian moon-ring system Uranian rings scheme.png
Schematic of the Uranian moon–ring system

As of 2024, Uranus is known to have 13 inner moons, whose orbits all lie inside that of Miranda. [12] The inner moons are classified into two groups based on similar orbital distances: these are the Portia group, which includes the six moons Bianca, Cressida, Desdemona, Juliet, Portia, and Rosalind; and the Belinda group, which includes the three moons Cupid, Belinda, and Perdita. [12] [22] All of the inner moons are intimately connected with the rings of Uranus, which probably resulted from the fragmentation of one or several small inner moons. [23] The two innermost moons, Cordelia and Ophelia, are shepherds of Uranus's ε ring, whereas the small moon Mab is a source of Uranus's outermost μ ring. [12] There may be two additional small (2–7 km in radius) undiscovered shepherd moons located about 100 km exterior to Uranus's α and β rings. [24]

At 162 km, Puck is the largest of the inner moons of Uranus and the only one imaged by Voyager 2 in any detail. Puck and Mab are the two outermost inner satellites of Uranus. All inner moons are dark objects; their geometrical albedo is less than 10%. [25] They are composed of water ice contaminated with a dark material, probably radiation-processed organics. [26]

The inner moons constantly perturb each other, especially within the closely-packed Portia and Belinda groups. The system is chaotic and apparently unstable. [27] Simulations show that the moons may perturb each other into crossing orbits, which may eventually result in collisions between the moons. [12] Desdemona may collide with Cressida within the next million years, [28] and Cupid will likely collide with Belinda in the next 10 million years; Perdita and Juliet may be involved in later collisions. [29] Because of this, the rings and inner moons may be under constant flux, with moons colliding and re-accreting on short timescales. [29]

Large moons

Uranus and its six largest moons compared at their proper relative sizes and in the correct order. From left to right: Puck, Miranda, Ariel, Umbriel, Titania, and Oberon Uranus moons.jpg
Uranus and its six largest moons compared at their proper relative sizes and in the correct order. From left to right: Puck, Miranda, Ariel, Umbriel, Titania, and Oberon

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. [21] All these moons are relatively dark objects: their geometrical albedo varies between 30 and 50%, whereas their Bond albedo is between 10 and 23%. [25] Umbriel is the darkest moon and Ariel the brightest. The masses of the moons range from 6.7 × 1019 kg (Miranda) to 3.5 × 1021 kg (Titania). For comparison, the Moon has a mass of 7.5 × 1022 kg. [30] The major moons of Uranus are thought to have formed in the accretion disc, which existed around Uranus for some time after its formation or resulted from a large impact suffered by Uranus early in its history. [31] [32] This view is supported by their large thermal inertia, a surface property they share with dwarf planets like Pluto and Haumea. [33] It differs strongly from the thermal behaviour of the Uranian irregular moons that is comparable to classical trans-Neptunian objects. [34] This suggests a separate origin.

Moons (Ariel, Umbriel, Titania, Oberon, Miranda) Modeling (4 May 2023) PIA25500-Uranus-MajorMoons-20230504.jpg
Moons (Ariel, Umbriel, Titania, Oberon, Miranda)
Modeling (4 May 2023)

All major moons comprise approximately equal amounts rock and ice, except Miranda, which is made primarily of ice. [35] The ice component may include ammonia and carbon dioxide. [36] Their surfaces are heavily cratered, though all of them (except Umbriel) show signs of endogenic resurfacing in the form of lineaments (canyons) and, in the case of Miranda, ovoid race-track like structures called coronae. [2] Extensional processes associated with upwelling diapirs are likely responsible for the origin of the coronae. [37] Ariel appears to have the youngest surface with the fewest impact craters, while Umbriel's appears oldest. [2] A past 3:1 orbital resonance between Miranda and Umbriel and a past 4:1 resonance between Ariel and Titania are thought to be responsible for the heating that caused substantial endogenic activity on Miranda and Ariel. [38] [39] One piece of evidence for such a past resonance is Miranda's unusually high orbital inclination (4.34°) for a body so close to the planet. [40] [41] The largest Uranian moons may be internally differentiated, with rocky cores at their centers surrounded by ice mantles. [35] Titania and Oberon may harbor liquid water oceans at the core/mantle boundary. [35] The major moons of Uranus are airless bodies. For instance, Titania was shown to possess no atmosphere at a pressure larger than 10–20 nanobar. [42]

The path of the Sun in the local sky over the course of a local day during Uranus's and its major moons' summer solstice is quite different from that seen on most other Solar System worlds. The major moons have almost exactly the same rotational axial tilt as Uranus (their axes are parallel to that of Uranus). [2] The Sun would appear to follow a circular path around Uranus's celestial pole in the sky, at the closest about 7 degrees from it, [c] during the hemispheric summer. Near the equator, it would be seen nearly due north or due south (depending on the season). At latitudes higher than 7°, the Sun would trace a circular path about 15 degrees in diameter in the sky, and never set during the hemispheric summer, moving to a position over the celestial equator during the Uranian equinox, and then invisible below the horizon during the hemispheric winter.

Irregular moons

Irregular satellites of Jupiter (red), Saturn (green), Uranus (magenta) and Neptune (blue; including Triton), plotted by distance from their planet (semi-major axis) in the horizontal axis and orbital inclination in the vertical axis. The semi-major axis values are expressed as a fraction of the planet's Hill sphere's radius, while the inclination is expressed in degrees from the ecliptic. The radius of the Uranian Hill sphere is approximately 73 million km. The relative sizes of moons are indicated by the size of their symbols, and the Caliban group of Uranian moons is labeled. Data as of February 2024. Irregular moon orbits a vs. i.jpg
Irregular satellites of Jupiter (red), Saturn (green), Uranus (magenta) and Neptune (blue; including Triton), plotted by distance from their planet (semi-major axis) in the horizontal axis and orbital inclination in the vertical axis. The semi-major axis values are expressed as a fraction of the planet's Hill sphere's radius, while the inclination is expressed in degrees from the ecliptic. The radius of the Uranian Hill sphere is approximately 73 million km. The relative sizes of moons are indicated by the size of their symbols, and the Caliban group of Uranian moons is labeled. Data as of February 2024.

Uranus's irregular moons range in size from 120 to 200 km (Sycorax) to under 10 km (S/2023 U 1). [43] Due to the small number of known Uranian irregular moons, it is not yet clear which of them belong to groups with similar orbital characteristics. The only known group among Uranus's irregular moons is the Caliban group, which is clustered at orbital distances between 6–7 million km (3.7–4.3 million mi) and inclinations between 141°–144°. [14] The Caliban group includes three retrograde moons, which are Caliban, S/2023 U 1, Stephano. [14]

The intermediate inclinations 60° < i < 140° are devoid of known moons due to the Kozai instability. [3] In this instability region, solar perturbations at apoapse 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. [3] Margaret is the only known irregular prograde moon of Uranus, and it has one of the most eccentric orbits of any moon in the Solar System.

List

Orbital diagram of the orbital inclination and orbital distances for Uranus's rings and moon system at various scales. Open the image for full resolution. Uranusmoonsdiagram.png
Orbital diagram of the orbital inclination and orbital distances for Uranus's rings and moon system at various scales. Open the image for full resolution.

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 and bolded. The inner and major moons all have prograde orbits. Irregular moons with retrograde orbits are shown in dark grey. Margaret, the only known irregular moon of Uranus with a prograde orbit, is shown in light grey. The orbits and mean distances of the irregular moons are variable over short timescales due to frequent planetary and solar perturbations, therefore the listed orbital elements of all irregular moons are averaged over a 8,000-year numerical integration by Brozović and Jacobson (2009). These may differ from osculating orbital elements provided by other sources. [44] The orbital elements of major moons listed here are based on the epoch of 1 January 2000, [45] while orbital elements of irregular satellites are based on the epoch of 1 January 2020. [46]

Key
 Inner moons (13)♠ Major moons (5)♦ Caliban group (3)
† Margaret (1)‡ Ungrouped retrograde irregular moons (6)
Uranian moons
Label
[d] 		NamePronunciation
(key)		Image Abs.
magn.
[47] 		Diameter
(km)
[e] 		Mass
(× 1016  kg)
[f] 		Semi-major axis
(km)
[g] 		Orbital period
(d)
[g] [h] 		Inclination
(°)
[g] [i] 		Eccentricity
[g] 		Discovery
year
[50] 		Year announcedDiscoverer
[50] 		Group
VI Cordelia /kɔːrˈdiːliə/ Cordelia 01-24-86.png 10.340 ± 6
(50 × 36)		≈ 3.449800+0.334570.20.00019861986 Terrile
(Voyager 2)		ε ring shepherd
VII Ophelia /oʊˈfiːliə/ Opheliamoon.png 10.243 ± 8
(54 × 38)		≈ 4.253800+0.376860.10.01119861986 Terrile
(Voyager 2)		ε ring shepherd
VIII Bianca /biˈɑːŋkə/ Biancamoon.png 9.851 ± 4
(64 × 46)		≈ 6.959200+0.435010.10.00119861986 Smith
(Voyager 2)		Portia
IX Cressida /ˈkrɛsədə/ Cressida.png 8.980 ± 4
(92 × 74)		≈ 2761800+0.463150.10.00019861986 Synnott
(Voyager 2)		Portia
X Desdemona /ˌdɛzdəˈmoʊnə/ Desdemonamoon.png 9.364 ± 8
(90 × 54)		≈ 1462700+0.473230.10.00019861986 Synnott
(Voyager 2)		Portia
XI Juliet /ˈdʒuːliət/ Julietmoon.png 8.594 ± 8
(150 × 74)		≈ 4364400+0.493480.00.00119861986 Synnott
(Voyager 2)		Portia
XII Portia /ˈpɔːrʃə/ Portia1.jpg 7.7135 ± 8
(156 × 126)		≈ 13066100+0.513200.00.00019861986 Synnott
(Voyager 2)		Portia
XIII Rosalind /ˈrɒzələnd/ Rosalindmoon.png 9.172 ± 12≈ 2069900+0.558460.00.00019861986 Synnott
(Voyager 2)		Portia
XXVII Cupid /ˈkjuːpəd/ Cupidmoon.png 12.6≈ 18≈ 0.3174400+0.613170.10.00520032003 Showalter and
Lissauer 		Belinda
XIV Belinda /bəˈlɪndə/
Belinda.gif
8.890 ± 16
(128 × 64)		≈ 3875300+0.623530.00.00019861986 Synnott
(Voyager 2)		Belinda
XXV Perdita /ˈpɜːrdətə/ Perditamoon.png 11.030 ± 6≈ 1.476400+0.638410.00.00219991999 Karkoschka
(Voyager 2)		Belinda
XV Puck /ˈpʌk/
Puck.png
7.3162 ± 4191±6486005+0.761480.35620.000219851986 Synnott
(Voyager 2)
XXVI Mab /ˈmæb/
Mabmoon.png
12.1≈ 18≈ 0.3197700+0.923290.10.00320032003Showalter and
Lissauer		μ ring source
V Miranda ♠ /məˈrændə/
Miranda mosaic in color - Voyager 2.png
3.5471.6 ± 1.4
(481 × 468 × 466)		6293±300129858+1.41384.40720.001419481948 Kuiper
I Ariel ♠ /ˈɛəriɛl/
Ariel in monochrome.jpg
1.01157.8±1.2
(1162 × 1156 × 1155)		123310±1800190930+2.52070.01670.001218511851 Lassell
II Umbriel ♠ /ˈʌmbriəl/
PIA00040 Umbrielx2.47.jpg
1.71169.4±5.6128850±2250265982+4.14450.07960.003918511851 Lassell
III Titania ♠ /təˈtɑːniə/
Titania (moon) color, cropped.jpg
0.81576.8±1.2345500±5090436282+8.70640.11290.001217871787 Herschel
IV Oberon ♠ /ˈoʊbərɒn/
Voyager 2 picture of Oberon.jpg
1.01522.8±5.2311040±7490583449+13.4640.14780.001417871787 Herschel
XXII Francisco ‡ /frænˈsɪskoʊ/ 12.4≈ 22≈ 0.564275700−267146.80.14420012003 Holman et al.
XVI Caliban ♦ /ˈkæləbæn/ Caliban discovery.jpg 9.142+20
−12		≈ 3.97167000−580141.40.20019971997 Gladman et al.Caliban
XX Stephano ♦ /ˈstɛfənoʊ/ Stephano - Uranus moon.jpg 9.7≈ 32≈ 1.77951400−677143.60.23519991999 Gladman et al.Caliban
S/2023 U 1 ♦13.7≈ 8≈ 0.0277976600−681143.90.25020232024 Sheppard et al.Caliban
XXI Trinculo ‡ /ˈtrɪŋkjʊloʊ/ 12.7≈ 18≈ 0.318502600−749167.10.22020012002 Holman et al.
XVII Sycorax ‡ /ˈsɪkəræks/ Sycorax.jpg 7.4157+23
−15		≈ 20012193200−1286157.00.52019971997 Nicholson et al.
XXIII Margaret † /ˈmɑːrɡərət/ S2003u3acircle.gif 12.7≈ 20≈ 0.4214425000+165560.50.64220032003 Sheppard and
Jewitt
XVIII Prospero ‡ /ˈprɒspəroʊ/ Prospero - Uranus moon.jpg 10.5≈ 50≈ 6.516221000−1974149.40.44119991999 Holman et al.
XIX Setebos ‡ /ˈsɛtɛbʌs/ Uranus - Setebos image.jpg 10.7≈ 47≈ 5.417519800−2215153.90.57919991999 Kavelaars et al.
XXIV Ferdinand ‡ /ˈfɜːrdənænd/ Uranus moon 021002 02.jpg 12.5≈ 21≈ 0.4820421400−2788169.20.39520012003 Holman et al.

See also

Notes

  1. ↑ The mass of Triton is about 2.14 × 1022 kg, [20] whereas the combined mass of the Uranian moons is about 0.92 × 1022 kg.
  2. ↑ Uranus mass of 8.681 × 1025 kg / Mass of Uranian moons of 0.93 × 1022 kg
  3. ↑ The axial tilt of Uranus is 97°. [2]
  4. ↑ Label refers to the Roman numeral attributed to each moon in order of their discovery. [1]
  5. ↑ Diameters with multiple entries such as "60 × 40 × 34" reflect that the body is not a perfect spheroid and that each of its dimensions have been measured well enough. The diameters and dimensions of Miranda, Ariel, Umbriel, and Oberon were taken from Thomas, 1988. [21] The diameter of Titania is from Widemann, 2009. [42] The dimensions and radii of the inner moons are from Karkoschka, 2001, [11] except for Cupid and Mab, which were taken from Showalter, 2006. [12] The radii of outer moons except Sycorax and Caliban were taken from Sheppard's website. [43] The radii of Sycorax and Caliban are from Farkas-Takács et al., 2017. [48]
  6. ↑ Masses of Puck, Miranda, Ariel, Umbriel, Titania, and Oberon were taken from Jacobson, 2023 as reported in French, 2024. [49] Masses of all other moons were calculated assuming a density of 1 g/cm3 and using given radii.
  7. 1 2 3 4 Mean orbits of irregular satellites are taken from JPL Small System Dynamics, [46] while mean orbits of the five major moons and Puck are taken from Jacobson (2014). [45]
  8. ↑ Negative orbital periods indicate a retrograde orbit around Uranus (opposite to the planet's orbit).
  9. ↑ For regular satellites, inclination measures the angle between the moon's orbital plane and the plane defined by Uranus's equator. For irregular satellites, inclination measures the angle between the moon's orbital plane and the ecliptic.

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<span class="mw-page-title-main">Miranda (moon)</span> Moon of Uranus

Miranda, also designated Uranus V, is the smallest and innermost of Uranus's five round satellites. It was discovered by Gerard Kuiper on 16 February 1948 at McDonald Observatory in Texas, and named after Miranda from William Shakespeare's play The Tempest. Like the other large moons of Uranus, Miranda orbits close to its planet's equatorial plane. Because Uranus orbits the Sun on its side, Miranda's orbit is nearly perpendicular to the ecliptic and shares Uranus's extreme seasonal cycle.

<span class="mw-page-title-main">Umbriel</span> Moon of Uranus

Umbriel is the third-largest moon of Uranus. It was discovered on October 24, 1851, by William Lassell at the same time as neighboring moon Ariel. It was named after a character in Alexander Pope's 1712 poem The Rape of the Lock. Umbriel consists mainly of ice with a substantial fraction of rock, and may be differentiated into a rocky core and an icy mantle. The surface is the darkest among Uranian moons, and appears to have been shaped primarily by impacts, but the presence of canyons suggests early internal processes, and the moon may have undergone an early endogenically driven resurfacing event that obliterated its older surface.

<span class="mw-page-title-main">Uranus</span> Seventh planet from the Sun

Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a supercritical phase of matter, which astronomy calls "ice" or volatiles. The planet's atmosphere has a complex layered cloud structure and has the lowest minimum temperature of all the Solar System's planets. It has a marked axial tilt of 82.23° with a retrograde rotation period of 17 hours and 14 minutes. This means that in an 84-Earth-year orbital period around the Sun, its poles get around 42 years of continuous sunlight, followed by 42 years of continuous darkness.

<span class="mw-page-title-main">Puck (moon)</span> Moon of Uranus

Puck is the sixth-largest moon of Uranus. It was discovered in December 1985 by the Voyager 2 spacecraft. The name Puck follows the convention of naming Uranus's moons after characters from Shakespeare. The orbit of Puck lies between the rings of Uranus and the first of Uranus's large moons, Miranda. Puck is approximately spherical in shape and has diameter of about 162 km. It has a dark, heavily cratered surface, which shows spectral signs of water ice.

<span class="mw-page-title-main">Oberon (moon)</span> Moon of Uranus

Oberon, also designated Uranus IV, is the outermost and second-largest major moon of the planet Uranus. It is the second-most massive of the Uranian moons, and the tenth-largest moon in the Solar System. Discovered by William Herschel in 1787, Oberon is named after the mythical king of the fairies who appears as a character in Shakespeare's A Midsummer Night's Dream. Its orbit lies partially outside Uranus's magnetosphere.

<span class="mw-page-title-main">Cordelia (moon)</span> Moon of Uranus

Cordelia is the innermost known moon of Uranus. It was discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 7. It was not detected again until the Hubble Space Telescope observed it in 1997. Cordelia takes its name from the youngest daughter of Lear in William Shakespeare's King Lear. It is also designated Uranus VI.

<span class="mw-page-title-main">Ophelia (moon)</span> Moon of Uranus

Ophelia is a moon of Uranus. It was discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 8. It was not seen again until the Hubble Space Telescope recovered it in 2003. Ophelia was named after the daughter of Polonius, Ophelia, in William Shakespeare's play Hamlet. It is also designated Uranus VII.

<span class="mw-page-title-main">Bianca (moon)</span> Moon of Uranus

Bianca is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on January 23, 1986, and was given the temporary designation S/1986 U 9. It was named after the sister of Katherine in Shakespeare's play The Taming of the Shrew. It is also designated Uranus VIII.

<span class="mw-page-title-main">Cressida (moon)</span> Moon of Uranus

Cressida is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 9 January 1986, and was given the temporary designation S/1986 U 3. It was named after Cressida, the Trojan daughter of Calchas, a tragic heroine who appears in William Shakespeare's play Troilus and Cressida. It is also designated Uranus IX.

<span class="mw-page-title-main">Desdemona (moon)</span> Moon of Uranus

Desdemona is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 13 January 1986, and was given the temporary designation S/1986 U 6. Desdemona is named after the wife of Othello in William Shakespeare's play Othello. It is also designated Uranus X.

<span class="mw-page-title-main">Rosalind (moon)</span> Moon of Uranus

Rosalind is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 13 January 1986, and was given the temporary designation S/1986 U 4. It was named after the daughter of the banished Duke in William Shakespeare's play As You Like It. It is also designated Uranus XIII.

<span class="mw-page-title-main">Belinda (moon)</span> Moon of Uranus

Belinda is an inner satellite of the planet Uranus. Belinda was discovered from the images taken by Voyager 2 on 13 January 1986 and was given the temporary designation S/1986 U 5. It is named after the heroine of Alexander Pope's The Rape of the Lock. It is also designated Uranus XIV.

<span class="mw-page-title-main">Titania (moon)</span> Largest moon of Uranus

Titania, also designated Uranus III, is the largest moon of Uranus. At a diameter of 1,578 kilometres (981 mi) it is the eighth largest moon in the Solar System, with a surface area comparable to that of Australia. Discovered by William Herschel in 1787, it is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream. Its orbit lies inside Uranus's magnetosphere.

<span class="mw-page-title-main">Ariel (moon)</span> Fourth-largest moon of Uranus

Ariel is the fourth-largest moon of Uranus. Ariel orbits and rotates in the equatorial plane of Uranus, which is almost perpendicular to the orbit of Uranus, so the moon has an extreme seasonal cycle.

<span class="mw-page-title-main">Portia (moon)</span> Moon of Uranus

Portia is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 3 January 1986, and was given the temporary designation S/1986 U 1. The moon is named after Portia, the heroine of William Shakespeare's play The Merchant of Venice. It is also designated Uranus XII.

<span class="mw-page-title-main">Perdita (moon)</span> Moon of Uranus

Perdita is an inner satellite of Uranus. Perdita's discovery was very complicated, as the first photographs of Perdita were taken by the Voyager 2 spacecraft in 1986, but it was not recognized from the photographs for more than a decade. In 1999, the moon was noticed by Erich Karkoschka and reported. But because no further pictures could be taken to confirm its existence, it was officially demoted in 2001. However, in 2003, pictures taken by the Hubble Space Telescope managed to pick up an object where Perdita was supposed to be, finally confirming its existence.

<span class="mw-page-title-main">Mab (moon)</span> Moon of Uranus

Mab, or Uranus XXVI, is an inner satellite of Uranus. It was discovered by Mark R. Showalter and Jack J. Lissauer in 2003 using the Hubble Space Telescope. It was named after Queen Mab, a fairy queen from English folklore who is mentioned in William Shakespeare's play Romeo and Juliet.

<span class="mw-page-title-main">Moons of Neptune</span> Natural satellites of the planet Neptune

The planet Neptune has 16 known moons, which are named for minor water deities and a water creature in Greek mythology. By far the largest of them is Triton, discovered by William Lassell on 10 October 1846, 17 days after the discovery of Neptune itself. Over a century passed before the discovery of the second natural satellite, Nereid, in 1949, and another 40 years passed before Proteus, Neptune's second-largest moon, was discovered in 1989.

The naming of moons has been the responsibility of the International Astronomical Union's committee for Planetary System Nomenclature since 1973. That committee is known today as the Working Group for Planetary System Nomenclature (WGPSN).

<span class="mw-page-title-main">Rings of Uranus</span>

The rings of Uranus are intermediate in complexity between the more extensive set around Saturn and the simpler systems around Jupiter and Neptune. The rings of Uranus were discovered on March 10, 1977, by James L. Elliot, Edward W. Dunham, and Jessica Mink. William Herschel had also reported observing rings in 1789; modern astronomers are divided on whether he could have seen them, as they are very dark and faint.

References

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