A Guide to Planetary Satellites

Use these up-to-date tables to explore the wide-ranging assortment of moons, big and small, that populate our solar system.

Amalthea
Jupiter's inner moon Amalthea, discovered by E. E. Barnard in 1892 and seen at close range by NASA's Galileo spacecraft in 1999, is roughly 105 miles (170 km) across.
NASA / JPL.

Discovering a planetary satellite used to be a rare event. After the finding of Uranus's moon Miranda by Gerard Kuiper in 1948 and Jupiter's Ananke by Seth Nicholson in 1951, the total count of natural satellites stood at 31: Jupiter led with 12, followed by Saturn (9), Uranus (5), Neptune (2), Mars (2), and Earth (1). Telescopic observers added only a few more in the ensuing three decades — most notably Pluto's moon, Charon — as satellite discovery largely fell to NASA spacecraft. After Voyager 2's flyby of Neptune in 1989, the total had nearly doubled to 60.

However, the advent of sensitive electronic cameras has put telescopic observers back in the driver's seat, resulting in 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 their reality. While comets bear the surname(s) of their discoverer(s), and observers retain naming rights for asteroids, those who spot planetary moons must yield this 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.

The following is a tabulation of known planetary satellites, last updated in July 2013. As of then, the count stood at 173, distributed as follows: Earth 1, Mars 2, Jupiter 67, Saturn 62, Uranus 27, Neptune 14. Among the dwarf planets, Pluto has 5, Eris 1, and Haumea 2. However, the locations of 11 Jovian and seven Saturnian moonlets are known so poorly that they are effectively lost.

In the table below and on the following pages, the Diameter of each satellite and the Orbital distance from its planet's center (semimajor axis) are in kilometers; Eccentricity (Ecc.) 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) or the ecliptic plane (for outer moons). Names of "lost" objects are shown in italics.

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
EARTH      
Moon3,474–12.7384,40027.30.0555.1
       
MARS      
Phobos2211.49,3800.30.0151.1
Deimos1212.523,4601.30.0001.8

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
JUPITER      
Metis4417.5128,1000.30.0010.0
Adrastea1618.7128,9000.30.0020
Amalthea16814.1181,4000.50.0030.4
Thebe9816.0221,9000.70.0181.1
Io3,6435.0421,8001.80.0040.0
Europa3,1225.3671,1003.60.0090.5
Ganymede5,2624.61,070,4007.20.0010.2
Callisto4,8215.71,882,70016.70.0070.3
Themisto921.07,507,000130.00.24243.1
Leda1820.211,165,000240.90.16427.5
Himalia16014.811,461,000250.60.16227.5
Lysithea3818.211,717,000259.20.11228.3
Elara7816.611,741,000259.60.21726.6
S/2000 J11422.412,555,0002870.24828.3
Carpo323.016,989,000456.10.43051.4
S/2003 J12123.917,083,0004890.490160.0
Euporie223.119,302,000550.70.144145.8
S/2011 J1123.720,101,100582.20.296162.8
S/2003 J3223.420,220,0005840.198147.5
S/2010 J2123.920,307,200588.10.307150.4
S/2003 J18223.420,700,000606.30.119146.5
Orthosie223.120,721,000622.60.281146.5
Euanthe422.820,799,000620.60.232148.9
S/2003 J16223.320948000616.30.26148.6
Mneme223.321,036,000620.10.227148.6
Helike422.621,064,000626.30.156154.8
Harpalyke422.221,105,000623.30.226148.6
Praxidike721.221,147,000625.30.230149.0
Thelxinoe223.521,165,000628.10.221151.4
Thyone422.321,192,000627.20.229148.5
Iocaste521.821,272,000631.60.216149.4
Ananke2818.821,276,000629.80.244148.9
Hermippe422.121,300,000633.90.210150.7
S/2003 J15223.522,630,0006900.189146.5
S/2003 J10223.623,040,0007160.430165.1
Pasithee223.223,096,000719.50.267165.1
Herse223.423,097,000715.40.200164.2
Eurydome322.723,148,000717.30.276150.3
Chaldene422.523,179,000723.80.246165.2
Isonoe422.523,217,000725.50.247165.3
Kale223.023,217,000729.50.260165.0
S/2011 J2123.523,267,000725.10.387151.9
Kallichore223.723,273,000728.30.264165.5
Erinome322.823,279,000728.30.267164.9
S/2010 J1223.323,314,300723.20.320163.2
Aitne322.723,315,000730.10.264165.1
Arche322.823,355,000731.90.259165
Taygete521.923,360,000732.40.252165.2
S/2003 J9123.723,380,0007340.263165.0
S/2003 J23 >223.623,385,0007340.273146.4
Carme4617.923,404,000734.20.253164.9
S/2003 J5422.423,490,0007380.247165.2
S/2003 J19223.723,530,0007410.256165.1
Hegemone322.823,556,000739.90.328155.2
Kalyke521.823,583,000743.00.245165.2
Pasiphae5816.923,624,000743.60.409151.4
Eukelade422.623,661,000746.40.272165.5
Sponde223.023,790,000748.30.312151.0
Megaclite621.723,806,000752.80.421152.8
Cyllene223.223,878,0007520.319149.3
S/2003 J4223.023,930,0007560.362149.6
Sinope3818.323,939,000758.90.250158.1
Aoede422.523,981,000761.40.432158.3
Autonoe422.024,033,0007610.334152.9
Callirrhoe720.824,102,000758.80.283147.1
Kore223.624,543,000779.20.325145.0
S/2003 J2223.228,380,0009790.413157.1

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
SATURN      
S/2009 S10.328.0117,0000.50.0000.0
Pan2819.4133,5800.60.0000.0
Daphnis724.0136,5000.60.0000.0
Atlas3218.5137,6700.60.0010.0
Prometheus8615.8139,3800.60.0020.0
Pandora8116.4141,7200.60.0040.1
Epimetheus11315.6151,4100.70.0100.5
Janus17814.4151,4600.70.0070.2
Aegaeon0.525167,5000.80.0000.0
Mimas39712.8185,5400.90.0201.6
Methone323194,4401.00.0010.0
Anthe224197,7001.00.0010.1
Pallene423212,2801.20.0040.2
Enceladus49911.8238,0401.40.0050.0
Tethys1,06010.2294,6701.90.0001.1
Calypso2118.7294,7101.90.0011.5
Telesto2518.5294,7101.90.0001.2
Polydeuces423.0377,2002.70.0180.2
Dione1,11810.4377,4202.70.0020.0
Helene3118.4377,4202.70.0070.2
Rhea1,5289.6527,0704.50.0010.3
Titan5,1508.41,221,86016.00.0290.3
Hyperion28314.41,500,93021.30.0230.6
Iapetus1,43611.03,560,85079.30.0298.3
Kiviuq1422.011,3
11,100
449.10.16448.5
Ijiraq1022.611,367,400451.50.45847.1
Phoebe22016.412,947,910550.30.163175.2
Paaliaq1921.315,240,000687.50.54041.8
Skathi623.615,614,300728.10.293150.8
Albiorix2620.516,401,100783.50.48435.3
S/2007 S2624.416,720,0008070.179174.1
Bebhionn624.117,117,800834.90.48434.6
Erriapus923.017,611,400870.80.46838.6
Skoll624.517,663,300878.40.470160.2
Tarqeq723.917,909,900887.30.11949.6
Siarnaq3220.118,015,400896.40.40544.5
Tarvos1322.118,263,200925.80.53135.9
S/2004 S13624.518,410,0009350.259168.8
Hyrrokkin823.518,437,300931.80.329151.2
Greip624.418,442,200935.60.316173.3
Mundilfari623.818,667,900952.80.205169.2
S/2006 S1624.618,780,0009610.141156.2
S/2007 S3524.918,940,0009790.185177.6
Bergelmir624.219,338,3001005.80.142158.9
Jarnsaxa624.719,356,4001,007.00.217163.3
Narvi824.019,417,3001003.70.426175.4
S/2004 S17425.219,450,00010150.180168.2
Suttungr623.919,476,7001,016.70.114173.9
Hati624.419,775,0001,039.00.373165.0
S/2004 S12524.819,890,0
00
10450.327165.7
Bestla723.820,278,0001,087.40.474141.7
Farbauti524.720,387,0001,087.00.245158.0
Thrymr623.920,439,6001,094.10.466173.7
Aegir624.420,749,8001,117.80.252167.1
S/2004 S7624.521,000,0001,1400.529165.7
Kari723.922,077,1001230.80.484155.9
S/2006 S3624.622,100,1001227.10.404159.9
Fenrir42522,454,8001,260.40.133164.4
Surtur624.822,920,4001296.50.447169.1
Loge624.623,065,5001311.40.188167.1
Ymir1621.723,140,4001,315.60.334171.7
Fornjot624.625,151,2001494.20.210169.7

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
URANUS      
Cordelia4023.649,8000.30.0000.1
Ophelia2323.353,8000.40.0100.1
Bianca5122.559,2000.40.0010.2
Cressida8021.661,8000.50.0000.0
Desdemona6422.062,7000.50.0000.1
Juliet9421.164,4000.50.0010.1
Portia13520.466,1000.50.0000.1
Rosalind7221.869,9000.60.0000.3
Cupid102674,3900.60.0010.1
Belinda8121.575,3000.60.0000.0
Perdita4023.676,4200.60.0000.5
Puck16219.886,0000.80.0000.3
Mab102697,7400.900.1
Miranda47215.8129,9001.40.0014.3
Ariel1,15813.7190,9002.50.0010.0
Umbriel1,16914.5266,0004.10.0040.1
Titania1,57813.5436,3008.70.0010.1
Oberon1,52313.7583,50013.50.0010.1
Francisco12254,282,900267.10.132147.2
Caliban8922.47,231,100579.70.181140.9
Stephano2024.18,007,400677.50.225143.8
Trinculo1025.48,505,200749.40.219167.0
Sycorax19020.812,179,4001,288.40.522159.4
Margaret1125.214,146,7001,661.00.67757.4
Prospero3020.816,267,8001,978.40.444151.2
Setebos3023.317,420,4002,225.10.591158.2
Ferdinand1225.120,430,0002,790.00.399169.8
       
NEPTUNE      
Naiad5824.648,2300.30.0004.7
Thalassa8023.950,0700.30.0000.1
Despina14822.552,5300.30.0000.1
Galatea15822.461,9500.40.0010.0
Larissa19222.073,5500.60.0010.2
S/2004 N 12026.5105,2800.90.0000.0
Proteus41620.3117,6501.10.0010.1
Triton2,70713.5354,7605.90.000156.9
Nereid34019.75,513,820360.10.7517.1
Halimede5424.216,611,0001,879.10.265112.7
Sao3125.422,228,0002,912.70.13753.5
Laomedeia372523,567,0003,171.30.40037.9
Psamathe3625.148,096,0009,074.30.380126.3
Neso4324.749,285,0009,740.70.571136.4
       
PLUTO      
Charon1,18617.317,5366.40.00296.1
Styx102742,00020.20.00096.2
Nix10023.448,70824.90.00396.2
Kerberos20265950032.20.00096.2
Hydra1502364,74938.2 ass="TD">0.00596.4
       
ERIS      
Dysnomia2002337,35015.80.007142
       
HAUMEA      
Namaka17021.925,66018.30.249113.0
Hi'iaka31020.649,88049.50.051126.4

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