The Moons of the Solar System

By: The Editors of Sky & Telescope January 19, 2023 0

Use these up-to-date tables to learn about the moons of the solar system, including the plethora of Jupiter’s moons and the weird menagerie of Saturn’s moons.

Pandora, a moon of Saturn — Cassini snapped this image of Saturn's moon Pandora on December 21, 2016, from a range of 25,200 miles (40,500 kilometers).
*NASA / JPL / Space Science Institute*

Discovering a new moon in the solar system used to be a rare event. After Gerard Kuiper found Miranda, a moon of Uranus, in 1948 and Seth Nicholson found Ananke, a moon of Jupiter, in 1951, the total count of natural planetary satellites stood at 31: Jupiter's moons numbered 12, followed by the moons of Saturn (9), Uranus (5), Neptune (2), Mars (2), and Earth (1). (Notably, Mercury and Venus are the only planets in the solar system that do not have moons.)

In the ensuing three decades, finding solar system moons largely fell to NASA spacecraft. After Voyager 2's flyby of Neptune in 1989, the total number of solar system moons had nearly doubled to 60. However, the advent of sensitive electronic cameras has put ground-based observers back in the driver's seat, resulting in several dozens of finds over the past few years.

Indeed, some of the new objects are so small, only a few kilometers across, that they stretch the traditional notion of what constitutes a "moon." Sometimes faint objects appear fleetingly in images and are never seen again; others require patient follow-up observations over months or years to confirm that they orbit a planet.

While comets bear the surname(s) of their discoverer(s), and observers retain naming rights for asteroids, those who spot planetary moons must yield naming privilege to the International Astronomical Union. By convention, the IAU does not name a satellite until its orbit is known precisely — a threshold sometimes not reached until decades after the initial discovery.

Hyperion, a moon of Saturn — Hyperion, a porous, almost loufa-like moon of Saturn was imaged during a close flyby of NASA's Cassini spacecraft.
*NASA / ESA*

The following tables contain all the known moons of the solar system, including the dozens of moons circling Jupiter, Saturn, Uranus, and Neptune. As of March 2023, the count stood at 232, distributed as follows: Earth 1, Mars 2, Jupiter 95, Saturn 83, Uranus 27, Neptune 14. Among the IAU-approved dwarf planets: Pluto 5, Haumea 2, Makemake 1, Gonggong 1, Eris 1.

In the table below, the diameter of each satellite and the orbital distance from its planet’s center (semimajor axis) are in kilometers; eccentricity is the elongation of the satellite’s orbit; and inclination is the tilt of its orbit plane, in degrees, with respect to the planet’s equatorial plane (for inner moons and dwarf planets) or the ecliptic plane (for outer moons). Names of “lost” objects are shown in italics.

Moons of Earth and Mars

Planet/ Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
EARTH
Moon	3,474	–12.7	384,400	27.3	0.055	5.1
MARS
Phobos	22	11.4	9,380	0.3	0.015	1.1
Deimos	12	12.5	23,460	1.3	0.000	1.8

Moons of Jupiter

Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
Metis	44	17.5	128,000	0.3	0.000	0.0
Adrastea	16	18.7	129,000	0.3	0.000	0.0
Amalthea	168	14.1	181,400	0.5	0.003	0.4
Thebe	98	16.0	221,900	0.7	0.018	1.1
Io	3,643	5.0	421,800	1.8	0.004	0.0
Europa	3,122	5.3	671,100	3.5	0.009	0.5
Ganymede	5,262	4.6	1,070,400	7.2	0.001	0.2
Callisto	4,821	5.7	1,882,700	16.7	0.007	0.3
Themisto	9	21.0	7,398,500	130.0	0.340	43.8
Leda	18	20.2	11,146,400	241.0	0.162	28.6
Ersa	3	22.9	11,401,000	249.2	0.116	29.1
Himalia	160	14.8	11,440,600	250.6	0.160	28.1
S/2018 J2	3	16.5	11,467,500	250.9	0.118	29.4
Pandia	3	23.0	11,481,000	251.9	0.179	29.0
Lysithea	38	18.2	11,700,800	259.2	0.117	27.2
Elara	78	16.6	11,712,300	259.6	0.211	27.9
S/2011 J3	3	16.3	11,797,200	261.8	0.176	28.7
Dia	4	22.4	12,260,300	287.2	0.232	29.0
S/2018 J4	2	23.6	16,504,300	433.2	0.057	53.2
Carpo	3	23.0	17,042,300	456.3	0.416	53.2
Valetudo	1	24.0	18,694,200	527.6	0.217	34.5
Euporie	2	23.1	19,265,800	550.7	0.148	145.7
S/2003 J18	2	23.4	20,336,300	598.1	0.090	145.3
S/2021 J1	2	23.6	20,667,200	607.0	0.246	149.8
Eupheme	2	23.4	20,768,600	616.7	0.241	148.0
S/2010 J2	1	23.9	20,793,000	618.8	0.248	148.1
S/2016 J1	1	24.0	20,802,600	618.5	0.232	144.7
Mneme	2	23.3	20,821,000	620.1	0.247	148.0
Euanthe	3	22.8	20,827,000	620.4	0.239	148.0
S/2003 J16	2	23.3	20,882,600	622.9	0.243	148.0
Harpalyke	4	22.2	20,892,100	623.3	0.232	147.7
Orthosie	2	23.1	20,901,000	622.6	0.299	144.3
S/2022 J3	1	24.1	20,912,400	617.8	0.272	144.5
Helike	4	22.6	20,915,700	626.3	0.153	154.4
Praxidike	7	21.2	20,935,400	625.4	0.246	148.3
S/2017 J3	2	23.4	20,941,000	625.6	0.231	147.9
S/2003 J12	1	23.9	20,963,100	627.2	0.235	150.0
S/2017 J7	2	23.6	20,964,800	626.6	0.233	147.3
Thelxinoe	2	23.5	20,976,000	628.0	0.228	150.6
Thyone	4	22.3	20,978,000	627.2	0.233	147.5
S/2003 J2	2	23.2	20,997,700	628.8	0.225	150.2
Ananke	28	18.9	21,034,500	629.8	0.237	147.6
Iocaste	5	21.8	21,066,700	631.6	0.227	148.8
Hermippe	4	22.1	21,108,500	633.9	0.219	150.2
S/2021 J 2	1	23.7	21,140,600	628.0	0.341	150.1
S/2021 J 3	2	23.6	21,495,700	643.8	0.356	150.1
S/2017 J9	3	22.8	21,768,700	666.1	0.200	155.5
S/2022 J1	2	23.1	22,015,500	667.3	0.191	165.4
S/2016 J3	2	23.6	22,213,500	676.4	0.236	164.1
S/2022 J2	1	24.1	22,413,200	685.5	0.182	165.4
Philophrosyne	2	23.5	22,604,600	702.5	0.229	146.3
S/2018 J3	1	23.7	22,826,600	704.6	0.273	164.9
S/2021 J5	2	23.6	22,831,800	704.8	0.200	163.2
Pasithee	2	23.2	22,846,700	719.5	0.270	164.6
S/2017 J8	1	24	22,849,500	719.8	0.255	164.8
S/2003 J24	2	23.8	22,887,400	721.6	0.259	164.5
Eurydome	3	22.7	22,899,000	717.3	0.294	149.1
S/2011 J2	1	23.6	22,909,200	718.3	0.355	151.9
S/2003 J4	2	23.0	22,926,500	718.1	0.328	148.2
Chaldene	4	22.5	22,930,500	723.7	0.265	164.7
S/2021 J4	1	23.7	22,946,700	710.1	0.159	149.6
S/2017 J2	2	23.5	22,953,200	724.7	0.272	164.5
Isonoe	4	22.5	22,981,300	726.3	0.249	164.8
Kallichore	2	23.7	23,021,800	728.3	0.252	164.8
Erinome	3	22.8	23,032,900	728.5	0.276	164.4
Kale	2	23.0	23,052,600	729.6	0.262	164.6
Eirene	4	22.5	23,055,800	729.8	0.258	164.6
Aitne	3	22.7	23,064,400	730.1	0.277	164.6
Eukelade	4	22.6	23,067,400	730.3	0.277	164.6
Arche	3	22.8	23,097,800	731.9	0.261	164.6
Taygete	5	21.9	23,108,000	732.4	0.253	164.7
S/2016 J4	2	23.6	23,113,800	727.0	0.294	147.1
S/2011 J1	2	23.7	23,124,500	733.2	0.271	164.6
Carme	46	17.9	23,144.400	734.2	0.256	164.6
Herse	2	23.4	23,150,500	734.5	0.262	164.4
S/2003 J19	2	23.7	23,156,400	734.8	0.265	164.7
S/2010 J1	2	23.3	23,189,800	736.5	0.252	164.5
S/2003 J9	1	23.7	23,199,400	736.9	0.263	164.8
S/2017 J5	2	23.5	23,206,200	737.3	0.257	164.8
S/2017 J6	2	23.5	23,245,300	734.0	0.336	149.7
Kalyke	5	21.8	23,302,600	742.0	0.260	164.8
Hegemone	3	22.8	23,348,700	739.8	0.358	152.6
S/2021 J6	2	23.7	23,427,200	732.6	0.363	166.5
Pasiphae	58	16.9	23,468,200	743.6	0.412	148.4
Sponde	2	23.0	23,543.300	748.3	0.322	149.3
S/2003 J10	2	23.6	23,576.300	755.4	0.264	164.4
Megaclite	6	21.7	23,644,600	752.9	0.421	149.8
Cyllene	2	23.2	23,654,700	752.0	0.419	146.8
Sinope	38	18.3	23,683,900	758.9	0.264	157.3
S/2017 J1	2	23.8	23,744,800	756.4	0.328	145.8
Aoede	4	22.5	23,778,200	761.5	0.436	155.7
Autonoe	4	22.0	23,792,500	761.0	0.330	150.8
Callirrhoe	7	20.8	23,795,500	758.9	0.297	145.1
S/2003 J23	2	23.6	23,829,300	760.0	0.313	144.7
Kore	2	23.6	24,205,200	776.8	0.328	141.5

Moons of Saturn

Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
S/2009 S1	0.3	28.0	117,000	0.5	0.000	0.0
Pan	28	19.4	133,600	0.6	0.000	0.0
Daphnis	7	24.0	136,500	0.6	0.000	0.0
Atlas	32	18.5	137,700	0.6	0.001	0.0
Prometheus	86	15.8	139,400	0.6	0.002	0.0
Pandora	81	16.4	141,700	0.6	0.004	0.1
Epimetheus	113	15.6	151,400	0.7	0.020	0.3
Janus	178	14.4	151,500	0.7	0.007	0.2
Aegaeon	0.5	25.0	167,500	0.8	0.000	0.0
Mimas	397	12.8	185,600	0.9	0.020	1.6
Methone	3	23.0	194,700	1.0	0.000	0.0
Anthe	1	24.0	198,100	1.0	0.002	0.0
Pallene	4	23.0	212,300	1.2	0.004	0.2
Enceladus	499	11.8	238,400	1.4	0.005	0.0
Tethys	1,060	10.2	295,000	1.9	0.001	1.1
Telesto	25	18.5	295,000	1.9	0.001	1.2
Calypso	21	18.7	295,000	1.9	0.001	1.5
Polydeuces	4	23.0	377,600	2.7	0.019	0.2
Helene	31	18.4	377,600	2.7	0.007	0.2
Dione	1,118	10.4	377,700	2.7	0.002	0.0
Rhea	1,528	9.6	527,200	4.5	0.001	0.3
Titan	5,150	8.4	1,221,900	16.0	0.029	0.3
Hyperion	283	14.4	1,481,500	21.3	0.105	0.6
Iapetus	1,436	11.0	3,561,700	79.3	0.028	7.6
S/2019 S1	6	25.1	11,244,000	445.6	0.541	46.7
Kiviuq	14	22.0	11,307,300	449.1	0.182	48.9
Ijiraq	10	22.6	11,344,600	451.5	0.353	49.2
Phoebe	220	16.4	12,929,400	550.3	0.164	175.2
Paaliaq	19	21.3	14,997,300	687.0	0.384	47.1
Skathi	6	23.6	15,575,100	728.1	0.265	149.7
S/2007 S2	6	24.4	15,939,700	754.9	0.232	175.6
S/2004 S37	4	25.1	15,940,500	754.5	0.446	159.3
Albiorix	26	20.5	16,329,100	783.5	0.470	38.9
Bebhionn	6	24.1	17,028,900	834.9	0.482	37.4
S/2004 S29	4	24.9	17,063,900	837.8	0.485	38.6
S/2004 S31	4	24.9	17,495,400	866.2	0.202	48.3
Erriapus	9	23.0	17,507,200	871.1	0.462	38.7
Skoll	6	24.5	17,625,700	878.4	0.470	158.4
Tarqeq	7	23.9	17,748,200	885.0	0.119	49.7
Siarnaq	32	20.1	17,880,800	895.9	0.311	48.2
Greip	4	25.1	18,206,000	921.2	0.326	179.8
Tarvos	13	22.1	18,215,200	926.4	0.528	38.6
Hyrrokkin	8	23.5	18,342,600	931.9	0.331	150.3
S/2004 S13	6	24.5	18,455,800	942.6	0.266	168.9
Mundilfari	6	23.8	18,590,300	952.9	0.210	168.4
S/2006 S1	6	24.6	18,745,600	964.2	0.105	155.2
Gridr	6	24.4	19,250,700	1,004.8	0.187	163.9
Bergelmir	6	24.2	19,269,100	1,005.6	0.144	158.7
Jarnsaxa	6	24.7	19,279,700	1,006.9	0.21	163
Narvi	8	24.0	19,286,500	1,003.8	0.449	143.7
Suttungr	6	23.9	19,391,700	1,016.7	0.116	175.0
S/2004 S17	4	25.2	19,408,100	1,017.5	0.179	167.9
S/2007 S3	5	24.9	19,513,700	1,026.4	0.162	175.6
Hati	6	24.4	19,697,100	1,040.3	0.375	165.0
S/2004 S12	5	24.8	19,770,700	1,046.1	0.325	163.0
Eggther	4	24.5	19,884,700	1,052.3	0.157	165.0
Farbauti	5	24.7	20,292,500	1,087.3	0.248	157.1
Thrymr	6	23.9	20,326,500	1,091.8	0.467	174.8
Bestla	7	23.8	20,337,900	1,087.5	0.461	136.3
S/2004 S7	6	24.5	20,435,200	1,100.0	0.462	163.3
Angrboda	3	25.3	20,591,000	1,114.1	0.216	177.4
Aegir	6	24.4	20,664,600	1,119.3	0.255	166.9
Beli	3	25.4	20,703,800	1,121.8	0.087	157.3
Gerd	3	25.2	20,947,500	1,143.0	0.517	174.4
Gunnlod	4	25.0	21,141,900	1,158.0	0.251	160.4
S/2006 S3	6	24.6	21,352,700	1,174.7	0.443	157.3
Skrymir	4	24.8	21,448,000	1,185.1	0.437	175.6
S/2004 S28	4	24.9	21,867,800	1,220.8	0.160	169.4
Alvaldi	4	24.6	21,995,600	1,232.2	0.238	177.4
Kari	7	23.9	22,029,700	1,231.0	0.482	153.0
Geirrod	4	25.1	22,259,500	1,251.1	0.539	154.4
Fenrir	4	25.0	22,331,800	1,260.3	0.136	164.3
Surtur	6	24.8	22,753,800	1,296.5	0.449	168.3
Loge	6	24.6	22,918,300	1,311.8	0.192	166.9
Ymir	16	21.7	22,957,100	1,315.2	0.337	173.1
S/2004 S21	3	25.4	23,125,000	1,325.3	0.409	155.0
S/2004 S39	2	25.5	23,195,400	1,336.2	0.102	167.1
S/2004 S24	3	25.2	23,339,900	1,341.3	0.072	36.5
S/2004 S36	3	25.3	23,433,600	1,353,2	0.617	152.5
Thiazzi	4	25.0	23,577,500	1,366.7	0.511	158.8
S/2004 S34	3	25.3	24,145,500	1420.8	0.279	168.3
Fornjot	6	24.6	24,937,300	1,494.0	0.214	169.5
S/2004 S26	4	25.0	26,097,100	1603.9	0.148	172.9

Moons of Uranus

Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
Cordelia	40	23.6	49,800	0.3	0.000	0.2
Ophelia	23	23.3	53,800	0.4	0.011	0.1
Bianca	51	22.5	59,200	0.4	0.001	0.2
Cressida	80	21.6	61,800	0.5	0.000	0.1
Desdemona	64	22.0	62,700	0.5	0.000	0.1
Juliet	94	21.1	64,400	0.5	0.001	0.0
Portia	135	20.4	66,100	0.5	0.000	0.0
Rosalind	72	21.8	69,900	0.6	0.000	0.0
Cupid	10	26.0	74,400	0.6	0.005	0.1
Belinda	81	21.5	75,300	0.6	0.000	0.0
Perdita	40	23.6	76,400	0.6	0.002	0
Puck	162	19.8	86,000	0.8	0.000	0.3
Mab	10	26.0	97,700	0.9	0.003	0.1
Miranda	472	15.8	129,900	1.4	0.001	4.4
Ariel	1,158	13.7	190,900	2.5	0.001	0.0
Umbriel	1,169	14.5	266,000	4.1	0.004	0.1
Titania	1,578	13.5	436,300	8.7	0.001	0.1
Oberon	1,523	13.7	583,400	13.5	0.001	0.1
Francisco	12	25.0	4,283,000	267.1	0.139	147.4
Caliban	89	22.4	7,230,000	579.7	0.204	142.0
Stephano	20	24.1	8,004,000	677.5	0.218	143.9
Trinculo	10	25.4	8,505,000	749.6	0.219	167.1
Sycorax	190	20.8	12,180,000	1,289.2	0.521	159.3
Margaret	11	25.2	14,070,000	1,648.1	0.678	57.7
Prospero	30	20.8	16,267,000	1,980.4	0.439	151.7
Setebos	30	23.3	17,444,000	2,228.7	0.588	158.2
Ferdinand	12	25.1	20,648,000	2,816.3	0.397	169.8

Moons of Neptune

Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
Naiad	76	24.6	48,200	0.3	0.000	4.7
Thalassa	92	23.9	50,100	0.3	0.000	0.2
Despina	146	22.5	52,500	0.3	0.000	0.0
Galatea	179	22.4	62,000	0.4	0.000	0.0
Larissa	179	22.0	73,500	0.6	0.001	0.2
Hippocamp	35	26.5	105,300	1.0	0.001	0.3
Proteus	407	20.3	117,600	1.1	0.000	0.0
Triton	2,707	13.5	354,800	5.9	0.000	157.3
Nereid	340	19.7	5,504,000	360.1	0.749	5.8
Halimede	54	24.2	15,753,700	1,879.5	0.566	133.8
Sao	31	25.4	22,381,400	2,914.3	0.299	48.2
Laomedeia	37	25.0	23,607,900	3,179.6	0.418	34.8
Psamathe	36	25.1	46,701,600	9,110.4	0.451	137.1
Neso	43	24.7	50,045,900	9,617.8	0.447	132.3

Moons of Pluto

Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
Charon	1,186	17.3	19,600	6.4	0.000	0.0
Styx	12	27.0	42,400	20.2	0	0.0
Nix	45	23.4	48,700	24.9	0.000	0.0
Kerberos	14	26.0	57,800	31.9	0.000	0.4
Hydra	45	23.0	64,700	38.5	0.006	0.3

Moons of Other Dwarf Planets

Object/ Satellite	Diameter (km)	Visual magnitude	Distance (km)	Orbital period (days)	Eccen- tricity	Inclina- tion (°)
HAUMEA
Namaka	170	21.9	25,700	18.3	0.249	113.0
Hiʻiaka	310	20.6	49,900	49.5	0.051	126.4
QUAOAR
Weywot	75	24.9	14,500	12.4	0.15	14
MAKEMAKE
S/2015 (136472) 1	175	25.2	>21,000	>12	?	?
GONGGONG
Xiangliu	250	26.0	24,000	35–100	0.3	83 or 119
ERIS
Dysnomia	350	25.6	37,350	15.8	0.007	142