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            
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

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
JUPITER            
Metis 44 17.5 128,100 0.3 0.001 0.0
Adrastea 16 18.7 128,900 0.3 0.002 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 3.6 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 7,507,000 130.0 0.242 43.1
Leda 18 20.2 11,165,000 240.9 0.164 27.5
Himalia 160 14.8 11,461,000 250.6 0.162 27.5
Lysithea 38 18.2 11,717,000 259.2 0.112 28.3
Elara 78 16.6 11,741,000 259.6 0.217 26.6
S/2000 J11 4 22.4 12,555,000 287 0.248 28.3
Carpo 3 23.0 16,989,000 456.1 0.430 51.4
S/2003 J12 1 23.9 17,083,000 489 0.490 160.0
Euporie 2 23.1 19,302,000 550.7 0.144 145.8
S/2011 J1 1 23.7 20,101,100 582.2 0.296 162.8
S/2003 J3 2 23.4 20,220,000 584 0.198 147.5
S/2010 J2 1 23.9 20,307,200 588.1 0.307 150.4
S/2003 J18 2 23.4 20,700,000 606.3 0.119 146.5
Orthosie 2 23.1 20,721,000 622.6 0.281 146.5
Euanthe 4 22.8 20,799,000 620.6 0.232 148.9
S/2003 J16 2 23.3 20948000 616.3 0.26 148.6
Mneme 2 23.3 21,036,000 620.1 0.227 148.6
Helike 4 22.6 21,064,000 626.3 0.156 154.8
Harpalyke 4 22.2 21,105,000 623.3 0.226 148.6
Praxidike 7 21.2 21,147,000 625.3 0.230 149.0
Thelxinoe 2 23.5 21,165,000 628.1 0.221 151.4
Thyone 4 22.3 21,192,000 627.2 0.229 148.5
Iocaste 5 21.8 21,272,000 631.6 0.216 149.4
Ananke 28 18.8 21,276,000 629.8 0.244 148.9
Hermippe 4 22.1 21,300,000 633.9 0.210 150.7
S/2003 J15 2 23.5 22,630,000 690 0.189 146.5
S/2003 J10 2 23.6 23,040,000 716 0.430 165.1
Pasithee 2 23.2 23,096,000 719.5 0.267 165.1
Herse 2 23.4 23,097,000 715.4 0.200 164.2
Eurydome 3 22.7 23,148,000 717.3 0.276 150.3
Chaldene 4 22.5 23,179,000 723.8 0.246 165.2
Isonoe 4 22.5 23,217,000 725.5 0.247 165.3
Kale 2 23.0 23,217,000 729.5 0.260 165.0
S/2011 J2 1 23.5 23,267,000 725.1 0.387 151.9
Kallichore 2 23.7 23,273,000 728.3 0.264 165.5
Erinome 3 22.8 23,279,000 728.3 0.267 164.9
S/2010 J1 2 23.3 23,314,300 723.2 0.320 163.2
Aitne 3 22.7 23,315,000 730.1 0.264 165.1
Arche 3 22.8 23,355,000 731.9 0.259 165
Taygete 5 21.9 23,360,000 732.4 0.252 165.2
S/2003 J9 1 23.7 23,380,000 734 0.263 165.0
S/2003 J23 > 2 23.6 23,385,000 734 0.273 146.4
Carme 46 17.9 23,404,000 734.2 0.253 164.9
S/2003 J5 4 22.4 23,490,000 738 0.247 165.2
S/2003 J19 2 23.7 23,530,000 741 0.256 165.1
Hegemone 3 22.8 23,556,000 739.9 0.328 155.2
Kalyke 5 21.8 23,583,000 743.0 0.245 165.2
Pasiphae 58 16.9 23,624,000 743.6 0.409 151.4
Eukelade 4 22.6 23,661,000 746.4 0.272 165.5
Sponde 2 23.0 23,790,000 748.3 0.312 151.0
Megaclite 6 21.7 23,806,000 752.8 0.421 152.8
Cyllene 2 23.2 23,878,000 752 0.319 149.3
S/2003 J4 2 23.0 23,930,000 756 0.362 149.6
Sinope 38 18.3 23,939,000 758.9 0.250 158.1
Aoede 4 22.5 23,981,000 761.4 0.432 158.3
Autonoe 4 22.0 24,033,000 761 0.334 152.9
Callirrhoe 7 20.8 24,102,000 758.8 0.283 147.1
Kore 2 23.6 24,543,000 779.2 0.325 145.0
S/2003 J2 2 23.2 28,380,000 979 0.413 157.1

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
SATURN            
S/2009 S1 0.3 28.0 117,000 0.5 0.000 0.0
Pan 28 19.4 133,580 0.6 0.000 0.0
Daphnis 7 24.0 136,500 0.6 0.000 0.0
Atlas 32 18.5 137,670 0.6 0.001 0.0
Prometheus 86 15.8 139,380 0.6 0.002 0.0
Pandora 81 16.4 141,720 0.6 0.004 0.1
Epimetheus 113 15.6 151,410 0.7 0.010 0.5
Janus 178 14.4 151,460 0.7 0.007 0.2
Aegaeon 0.5 25 167,500 0.8 0.000 0.0
Mimas 397 12.8 185,540 0.9 0.020 1.6
Methone 3 23 194,440 1.0 0.001 0.0
Anthe 2 24 197,700 1.0 0.001 0.1
Pallene 4 23 212,280 1.2 0.004 0.2
Enceladus 499 11.8 238,040 1.4 0.005 0.0
Tethys 1,060 10.2 294,670 1.9 0.000 1.1
Calypso 21 18.7 294,710 1.9 0.001 1.5
Telesto 25 18.5 294,710 1.9 0.000 1.2
Polydeuces 4 23.0 377,200 2.7 0.018 0.2
Dione 1,118 10.4 377,420 2.7 0.002 0.0
Helene 31 18.4 377,420 2.7 0.007 0.2
Rhea 1,528 9.6 527,070 4.5 0.001 0.3
Titan 5,150 8.4 1,221,860 16.0 0.029 0.3
Hyperion 283 14.4 1,500,930 21.3 0.023 0.6
Iapetus 1,436 11.0 3,560,850 79.3 0.029 8.3
Kiviuq 14 22.0 11,3
11,100
449.1 0.164 48.5
Ijiraq 10 22.6 11,367,400 451.5 0.458 47.1
Phoebe 220 16.4 12,947,910 550.3 0.163 175.2
Paaliaq 19 21.3 15,240,000 687.5 0.540 41.8
Skathi 6 23.6 15,614,300 728.1 0.293 150.8
Albiorix 26 20.5 16,401,100 783.5 0.484 35.3
S/2007 S2 6 24.4 16,720,000 807 0.179 174.1
Bebhionn 6 24.1 17,117,800 834.9 0.484 34.6
Erriapus 9 23.0 17,611,400 870.8 0.468 38.6
Skoll 6 24.5 17,663,300 878.4 0.470 160.2
Tarqeq 7 23.9 17,909,900 887.3 0.119 49.6
Siarnaq 32 20.1 18,015,400 896.4 0.405 44.5
Tarvos 13 22.1 18,263,200 925.8 0.531 35.9
S/2004 S13 6 24.5 18,410,000 935 0.259 168.8
Hyrrokkin 8 23.5 18,437,300 931.8 0.329 151.2
Greip 6 24.4 18,442,200 935.6 0.316 173.3
Mundilfari 6 23.8 18,667,900 952.8 0.205 169.2
S/2006 S1 6 24.6 18,780,000 961 0.141 156.2
S/2007 S3 5 24.9 18,940,000 979 0.185 177.6
Bergelmir 6 24.2 19,338,300 1005.8 0.142 158.9
Jarnsaxa 6 24.7 19,356,400 1,007.0 0.217 163.3
Narvi 8 24.0 19,417,300 1003.7 0.426 175.4
S/2004 S17 4 25.2 19,450,000 1015 0.180 168.2
Suttungr 6 23.9 19,476,700 1,016.7 0.114 173.9
Hati 6 24.4 19,775,000 1,039.0 0.373 165.0
S/2004 S12 5 24.8 19,890,0
00
1045 0.327 165.7
Bestla 7 23.8 20,278,000 1,087.4 0.474 141.7
Farbauti 5 24.7 20,387,000 1,087.0 0.245 158.0
Thrymr 6 23.9 20,439,600 1,094.1 0.466 173.7
Aegir 6 24.4 20,749,800 1,117.8 0.252 167.1
S/2004 S7 6 24.5 21,000,000 1,140 0.529 165.7
Kari 7 23.9 22,077,100 1230.8 0.484 155.9
S/2006 S3 6 24.6 22,100,100 1227.1 0.404 159.9
Fenrir 4 25 22,454,800 1,260.4 0.133 164.4
Surtur 6 24.8 22,920,400 1296.5 0.447 169.1
Loge 6 24.6 23,065,500 1311.4 0.188 167.1
Ymir 16 21.7 23,140,400 1,315.6 0.334 171.7
Fornjot 6 24.6 25,151,200 1494.2 0.210 169.7

Confirmed List of Planetary Satellites
 
Satellite
Diameter
(km)
Visual
magnitude
Distance
(km)
Orbital
period (days)
Eccen-
tricity
Inclina-
tion (°)
URANUS            
Cordelia 40 23.6 49,800 0.3 0.000 0.1
Ophelia 23 23.3 53,800 0.4 0.010 0.1
Bianca 51 22.5 59,200 0.4 0.001 0.2
Cressida 80 21.6 61,800 0.5 0.000 0.0
Desdemona 64 22.0 62,700 0.5 0.000 0.1
Juliet 94 21.1 64,400 0.5 0.001 0.1
Portia 135 20.4 66,100 0.5 0.000 0.1
Rosalind 72 21.8 69,900 0.6 0.000 0.3
Cupid 10 26 74,390 0.6 0.001 0.1
Belinda 81 21.5 75,300 0.6 0.000 0.0
Perdita 40 23.6 76,420 0.6 0.000 0.5
Puck 162 19.8 86,000 0.8 0.000 0.3
Mab 10 26 97,740 0.9 0 0.1
Miranda 472 15.8 129,900 1.4 0.001 4.3
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 13.7 583,500 13.5 0.001 0.1
Francisco 12 25 4,282,900 267.1 0.132 147.2
Caliban 89 22.4 7,231,100 579.7 0.181 140.9
Stephano 20 24.1 8,007,400 677.5 0.225 143.8
Trinculo 10 25.4 8,505,200 749.4 0.219 167.0
Sycorax 190 20.8 12,179,400 1,288.4 0.522 159.4
Margaret 11 25.2 14,146,700 1,661.0 0.677 57.4
Prospero 30 20.8 16,267,800 1,978.4 0.444 151.2
Setebos 30 23.3 17,420,400 2,225.1 0.591 158.2
Ferdinand 12 25.1 20,430,000 2,790.0 0.399 169.8
             
NEPTUNE            
Naiad 58 24.6 48,230 0.3 0.000 4.7
Thalassa 80 23.9 50,070 0.3 0.000 0.1
Despina 148 22.5 52,530 0.3 0.000 0.1
Galatea 158 22.4 61,950 0.4 0.001 0.0
Larissa 192 22.0 73,550 0.6 0.001 0.2
S/2004 N 1 20 26.5 105,280 0.9 0.000 0.0
Proteus 416 20.3 117,650 1.1 0.001 0.1
Triton 2,707 13.5 354,760 5.9 0.000 156.9
Nereid 340 19.7 5,513,820 360.1 0.751 7.1
Halimede 54 24.2 16,611,000 1,879.1 0.265 112.7
Sao 31 25.4 22,228,000 2,912.7 0.137 53.5
Laomedeia 37 25 23,567,000 3,171.3 0.400 37.9
Psamathe 36 25.1 48,096,000 9,074.3 0.380 126.3
Neso 43 24.7 49,285,000 9,740.7 0.571 136.4
             
PLUTO            
Charon 1,186 17.3 17,536 6.4 0.002 96.1
Styx 10 27 42,000 20.2 0.000 96.2
Nix 100 23.4 48,708 24.9 0.003 96.2
Kerberos 20 26 59500 32.2 0.000 96.2
Hydra 150 23 64,749 38.2 ass="TD">0.005 96.4
             
ERIS            
Dysnomia 200 23 37,350 15.8 0.007 142
             
HAUMEA            
Namaka 170 21.9 25,660 18.3 0.249 113.0
Hi'iaka 310 20.6 49,880 49.5 0.051 126.4

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