Uranus' natural satellites

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Uranus has twenty-seven known moons. The first two moons (Titania and Oberon) were discovered by William Herschel on March 13, 1787. Two more moons (Ariel and Umbriel) were discovered by William Lassell in 1851. In 1852, Herschel's son John Herschel gave the four then-known 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.^[1]

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.

1 The natural satellites
- 1.1 Irregular satellites
2 Naming notes
3 References
4 External links

[edit] The natural satellites

Image:Uranian moon hellmontage.jpg

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.

**Notes:** * Awaiting confirmation and naming; ** Negative orbital periods indicate a retrograde orbit around Uranus (opposite to the planet's rotation).
Order	Name (spheroidal moons in bold) (Pronunciation key)			Mean diameter (km)	Mass (kg)	Semi-major axis (km)	Orbital period (day)	Inclination (°) (to Uranus' equator)	Discovery date
1	Uranus VI	Cordelia	IPA: [kʰɔɹˈdi.li.ə]	40 ± 6	4.5×10¹⁶?	49,770	0.335034	0.147°	1986
2	Uranus VII	Ophelia	IPA: [oʊˈfi.li.ə]	43 ± 8	5.4×10¹⁶?	53,790	0.376400	0.093°	1986
3	Uranus VIII	Bianca	IPA: [baɪˈæŋ.kə]	51 ± 4	9.3×10¹⁶?	59,170	0.434579	0.162°	1986
4	Uranus IX	Cressida	IPA: [ˈkʰɹɛ.sə.də]	80 ± 4	3.43×10¹⁷?	61,780	0.463570	0.038°	1986
5	Uranus X	Desdemona	IPA: [ˌdɛz.dəˈmoʊ.nə]	64 ± 8	1.78×10¹⁷?	62,680	0.473650	0.164°	1986
6	Uranus XI	Juliet	IPA: [ˈdʒu.liˌɛt]	94 ± 8	5.57×10¹⁷?	64,350	0.493065	0.056°	1986
7	Uranus XII	Portia	IPA: [ˈpʰɔɹ.ʃə]	135 ± 8	1.68×10¹⁸?	66,090	0.513196	0.087°	1986
8	Uranus XIII	Rosalind	IPA: [ˈɹɑ.zəˌlɪnd]	72 ± 12	2.54×10¹⁷?	69,940	0.558460	0.285°	1986
9	Uranus XXVII	Cupid	IPA: [ˈkʰju.pɪd]	~ 17.8	3.8×10¹⁵?	74,800	0.618	0.1°	2003
10	Uranus XIV	Belinda	IPA: [bəˈlɪn.də]	81 ± 16	3.57×10¹⁷?	75,260	0.623527	0.031°	1986
11	Uranus XXV	Perdita	IPA: [ˈpʰɚ.də.tə]	~ 26.6	1.3×10¹⁶?	76,420	0.638	0.07°	1986
12	Uranus XV	Puck	IPA: [ˈpʰʌk]	162 ± 4	2.89×10¹⁸?	86,010	0.761833	0.318°	1985
13	Uranus XXVI	Mab	IPA: [ˈmæb]	~ 24.8	1.0×10¹⁶?	97,734	0.923	0.1335°	2003
14	Uranus V	Miranda	IPA: [mɪˈɹæn.də]	471.6 ± 1.4	(6.6 ± 0.7)×10¹⁹	129,390	1.413479	4.232°	1948
15	Uranus I	Ariel	IPA: [ˈe.ɹiˌɛl]	1157.8 ± 1.2	(1.35 ± 0.12)×10²¹	191,020	2.520379	0.260°	1851
16	Uranus II	Umbriel	IPA: [ˈʌm.bɹiˌɛl]	1169.4 ± 5.6	(1.17 ± 0.13)×10²¹	266,300	4.144177	0.205°	1851
17	Uranus III	Titania	IPA: [tʰaɪˈtʰeɪ.ni.ə]	1577.8 ± 3.6	(3.53 ± 0.09)×10²¹	435,910	8.705872	0.340°	1787
18	Uranus IV	Oberon	IPA: [ˈoʊ.bəˌɹɑn]	1522.8 ± 5.2	(3.01 ± 0.07)×10²¹	583,520	13.463239	0.058°	1787
19	Uranus XXII	Francisco	IPA: [frænˈsɪ.skoʊ]	~ 12	1.3×10¹⁵?	4,276,000	-267.12^**	147.459°	2001
20	Uranus XVI	Caliban	IPA: [ˈkʰæ.ləˌbæn]	~ 98	7.3×10¹⁷?	7,231,000	-579.39^**	139.885°	1997
21	Uranus XX	Stephano	IPA: [ˈstɛ.fəˌnoʊ]	~ 20	6×10¹⁵?	8,004,000	-677.48^**	141.873°	1999
22	Uranus XXI	Trinculo	IPA: [ˈtʰɹɪŋ.kjəˌloʊ]	~ 10	7.5×10¹⁴?	8,504,000	-748.83^**	166.252°	2001
23	Uranus XVII	Sycorax	IPA: [ˈsɪ.kəˌɹæks]	~ 190	5.4×10¹⁸?	12,179,000	-1285.62^**	152.456°	1997
24	Uranus XXIII	Margaret	IPA: [ˈmaɹ.gəˌɹɛt]	~ 11	1.3×10¹⁵?	14,345,000	+1654.32	51.455°	2003
25	Uranus XVIII	Prospero	IPA: [ˈpʰɹɑ.spəˌɹoʊ]	~ 30	2.1×10¹⁶?	16,256,000	-1962.95^**	146.017°	1999
26	Uranus XIX	Setebos	IPA: [ˈsɛ.təˌbɑs]	~ 30	2.1×10¹⁶?	17,418,000	-2196.35^**	145.883°	1999
27	Uranus XXIV	Ferdinand	IPA: [ˈfɚ.dəˌnænd]	~ 12	1.3×10¹⁵?	20,901,000	-2805.51^**	167.346°	2001

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.

[edit] Irregular satellites

Irregular satellites 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 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.^[2]

[edit] Naming notes

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 objects.

[edit] References

^ Showalter, Mark R.; Lissauer, Jack J. (2005-12-22). "The Second Ring-Moon System of Uranus: Discovery and Dynamics". Science Express. DOI:10.1126/science.1122882.
^ Scott S. Sheppard, David C. Jewitt, and Jan Kleyna An Ultradeep Survey for Irregular Satellites of Uranus: Limits to Completeness, The Astronomical Journal, 129 (2005), pages 518–525 (preprint)

[edit] External links

NASA's Hubble Discovers New Rings and Moons Around Uranus (STScI-2005-33, December 22, 2005)

v • d • e Moons of Uranus
Inner	Cordelia · Ophelia · Bianca · Cressida · Desdemona · Juliet · Portia · Rosalind · Cupid · Belinda · Perdita · Puck · Mab
Major (spheroid)	Miranda · Ariel · Umbriel · Titania · Oberon
Outer (irregular)	Francisco · Caliban · Stephano · Trinculo · Sycorax · Margaret · Prospero · Setebos · Ferdinand
See also Rings of Uranus

v • d • e Natural satellites of the Solar System
Planetary satellites	Terrestrial · Martian · Jovian · Saturnian · Uranian · Neptunian
Other satellite systems	Plutonian · Eridian · Asteroid satellites
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Inner satellites • Trojans • Irregulars • List • List by diameter • Timeline of discovery • Naming

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