Uranus' natural satellites

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Uranus has 27 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.<ref name="Showalter">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.</ref>

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.

Image:Uranian moon montage.jpg

1 The natural satellites
- 1.1 Irregular satellites
2 Naming notes
3 See also
4 External link
5 References

[edit] The natural satellites

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	kɒrˈdiliə	40 ± 6	4.5×10¹⁶?	49,770	0.335034		1986
2	Uranus VII	Ophelia	oʊˈfiliə	43 ± 8	5.4×10¹⁶?	53,790	0.376400		1986
3	Uranus VIII	Bianca	biˈæŋkə	51 ± 4	9.3×10¹⁶?	59,170	0.434579		1986
4	Uranus IX	Cressida	ˈkrɛsɪdə	80 ± 4	3.43×10¹⁷?	61,780	0.463570		1986
5	Uranus X	Desdemona	ˌdɛzdɪˈmoʊnə	64 ± 8	1.78×10¹⁷?	62,680	0.473650		1986
6	Uranus XI	Juliet	ˈdʒuliˌɛt	94 ± 8	5.57×10¹⁷?	64,350	0.493065		1986
7	Uranus XII	Portia	ˈpɒrʃə	135 ± 8	1.68×10¹⁸?	66,090	0.513196		1986
8	Uranus XIII	Rosalind	ˈrɒzəlɪnd	72 ± 12	2.54×10¹⁷?	69,940	0.558460		1986
9	Uranus XXVII	Cupid	ˈkjupɪd	~ 17.8	3.8×10¹⁵?	74,800	0.618		2003
10	Uranus XIV	Belinda	bɪˈlɪndə	81 ± 16	3.57×10¹⁷?	75,260	0.623527		1986
11	Uranus XXV	Perdita	ˈpərdɪtə	~ 26.6	1.3×10¹⁶?	76,420	0.638		1986
12	Uranus XV	Puck	ˈpʌk	162 ± 4	2.89×10¹⁸?	86,010	0.761833		1985
13	Uranus XXVI	Mab	ˈmæb	~ 24.8	1.0×10¹⁶?	97,734	0.923		2003
14	Uranus V	Miranda	mɪˈrændə	471.6 ± 1.4	(6.6 ± 0.7)×10¹⁹	129,390	1.413479		1948
15	Uranus I	Ariel	ˈeɪriɛl	1157.8 ± 1.2	(1.35 ± 0.12)×10²¹	191,020	2.520379		1851
16	Uranus II	Umbriel	ˈʌmbriɛl	1169.4 ± 5.6	(1.17 ± 0.13)×10²¹	266,300	4.144177		1851
17	Uranus III	Titania	taɪˈteɪniə	1577.8 ± 3.6	(3.53 ± 0.09)×10²¹	435,910	8.705872		1787
18	Uranus IV	Oberon	ˈoʊbəˌrɒn	1522.8 ± 5.2	(3.01 ± 0.07)×10²¹	583,520	13.463239		1787
19	Uranus XXII	Francisco	frænˈsɪskoʊ	~ 12	1.3×10¹⁵?	4,276,000	-267.12^**	147.459°	2001
20	Uranus XVI	Caliban	ˈkælɪbæn	~ 98	7.3×10¹⁷?	7,231,000	-579.39^**	139.885°	1997
21	Uranus XX	Stephano	ˈstɛfənoʊ	~ 20	6×10¹⁵?	8,004,000	-677.48^**	141.873°	1999
22	Uranus XXI	Trinculo	ˈtrɪŋkjuloʊ	~ 10	7.5×10¹⁴?	8,504,000	-748.83^**	166.252°	2001
23	Uranus XVII	Sycorax	ˈsɪkʊræks	~ 190	5.4×10¹⁸?	12,179,000	-1285.62^**	152.456°	1997
24	Uranus XXIII	Margaret	ˈmargərɛt	~ 11	1.3×10¹⁵?	14,345,000	+1654.32	51.455°	2003
25	Uranus XVIII	Prospero	ˈprɒspəroʊ	~ 30	2.1×10¹⁶?	16,256,000	-1962.95^**	146.017°	1999
26	Uranus XIX	Setebos	ˈsɛtɪbɒs	~ 30	2.1×10¹⁶?	17,418,000	-2196.35^**	145.883°	1999
27	Uranus XXIV	Ferdinand	ˈfərdɪnænd	~ 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

Image:TheIrregulars URANUS.svg 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.<ref name=SheppardJewittUranus2005> 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</ref>

[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 bodies.

[edit] See also

Image:Uranus symbol.svg edit Uranus' natural satellites
Cordelia · Ophelia · Bianca · Cressida · Desdemona · Juliet · Portia · Rosalind · Cupid · Belinda · Perdita · Puck · Mab Miranda · Ariel · Umbriel · Titania · Oberon Francisco · Caliban · Stephano · Trinculo · Sycorax · Margaret · Prospero · Setebos · Ferdinand
See also: Rings of Uranus

Solar System Natural Satellites v • d • e</div>
Planetary satellites:	Terran • Martian • Jovian • Saturnian • Uranian • Neptunian
Other satellite systems:	Plutonian • Eridian • Asteroid satellites

Largest satellites:	Ganymede • Titan • Callisto • Io • Earth's Moon • Europa • Triton Titania • Rhea • Oberon • Iapetus • Charon • Umbriel • Ariel • Dione • Tethys
See also: inner satellites • trojans • irregulars • list by diameter • discovery timeline • naming

The Solar System v • d • e</div>
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