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Moons of Jupiter

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Jupiter's outer moons and their highly inclined orbits.

Jupiter has sixty-three known natural satellites.

Discovery of the moons

The Galilean moons. From left to right, in order of increasing distance from Jupiter: Io, Europa, Ganymede, Callisto.
The Galilean moons and their orbits around Jupiter.

Although claims are made for the observation of one of Jupiter's moons by Chinese astronomer Gan De in 364 BC, the first certain observations of Jupiter's satellites are those of Galileo Galilei in 1610, who sighted the four large Galilean moons with his 33x telescope.

No additional satellites were discovered until E.E. Barnard observed Amalthea in 1892. Further discoveries, aided by telescopic photography, followed quickly over the course of the twentieth century, and by 1975, before the Voyagers reached Jupiter, the planet was known to have at least thirteen satellites.

The Voyager 1 mission discovered three inner moons in 1979, bringing the total then known to 16 (17 if one counted Themisto, which had been found but then lost in 1975). The total rested there until 1999. Since then, researchers using sensitive ground-based detectors have recovered Themisto and found a further 46 tiny moons in long, eccentric, generally retrograde orbits. They average 3 kilometres in diameter, and the largest is barely 9 km across. All of these moons are thought to be captured asteroidal or perhaps cometary bodies, possibly fragmented into several pieces, but very little is actually known about them. The total number of known moons of Jupiter now stands at 63, currently the most of any planet in the solar system. Many additional tiny moons may exist that have not yet been discovered.

The most recent discoveries

On October 6 1999, the Spacewatch project discovered an asteroid, 1999 UX18. But it was soon realised that this was in fact a previously undiscovered moon of Jupiter, now called Callirrhoe. One year later, between November 23 and December 5, 2000, the team led by Scott S. Sheppard and David C. Jewitt of the University of Hawaii began a systematic search for small irregular moons of Jupiter. The other members of the team included, at various times, Yanga R. Fernández, Eugene A. Magnier, Scott Dahm, Aaron Evans, Henry H. Hsieh, Karen J. Meech, John L. Tonry, David J. Tholen (all from the University of Hawaii), Jan Kleyna (Cambridge University), Brett J. Gladman (University of Toronto), John J. Kavelaars (Hertzberg Institute of Astrophysics), Jean-Marc Petit (Observatoire de Besançon) and Rhiannon Lynne Allen (University of Michigan / University of British Columbia).

The team used the world's two largest CCD cameras, mounted on two of the thirteen telescopes atop Mauna Kea in Hawaii: the Subaru (8.3 m diameter) and the Canada-France-Hawaii (3.6 m). The 2000 observations revealed ten new moons, putting the count at 28 (Themisto had been rediscovered at the beginning of 2000).

The following year, between December 9 and 11, 2001, eleven other moons were discovered, bringing the total to thirty-nine. The year 2002 bore less fruit, netting only one moon, Arche. However, four months later, between February 5 and 9, 2003, twenty-three more moons were found, making for a complete sum of sixty-three moons.

Table of known moons

The Jovian 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 blue; these are the "Galilean Moons", which are comparable in size to Earth's moon. Irregular (captured) moons are indicated by grey shading: light grey for prograde satellites, dark grey for retrograde.

Order Name

(Pronunciation key)

Image Diameter
(km) 		Mass
(kg) 		Semi-major axis
(km)(3) 		Orbital period
(d)(3)(4) 		Inclination (°)(5) Eccentricity Discovered Group
1 XVI Metis IPA: [ˈmi.tɨs]
File:Metis2.gif
 43 1.2E+17 127 690(1) +7h 4m 29s(2) 0.000° 0.0012 1980 Amalthea
2 XV Adrastea IPA: [ˌæd.rəˈsti.ə]
26×20×16 7.5E+15 128 690(1) +7h 9m 30s(2) 0.000° 0.0018 1979
3 V Amalthea IPA: [ˌæm.əlˈθi.ə]
262×146×134 2.1E+18 181 170(1) +11h 57m 22.67s(2) 0.360° 0.0031 1892
4 XIV Thebe IPA: [ˈθi.bi]
110×90 1.5E+18 221 700(1) +16h 11m 17s(2) 0.901° 0.0177 1980
5 I Io IPA: [ˈaɪ.oʊ]
3660.0×3637.4×3630.6 8.9E+22 421 700(1) +1.769137786(2) 0.050° 0.0041 1610 Galileans
6 II Europa IPA: [jʊˈroʊ.pə]
3121.6 4.8E+22 671 034(1) +3.551181041(2) 0.471° 0.0094 1610
7 III Ganymede IPA: [ˈgæn.ɨ.mid]
5262.4 1.5E+23 1 070 412(1) +7.15455296(2) 0.204° 0.0011 1610
8 IV Callisto IPA: [kəˈlɪs.toʊ]
4820.6 1.1E+23 1 882 709(1) +16.6890184(2) 0.205° 0.0074 1610
9 XVIII Themisto IPA: [θəˈmɪs.toʊ] 8 6.9E+14 7 393 216 +129.87 45.762° 0.2115 1975/2000 Themisto
10 XIII Leda IPA: [ˈli.də] 10 1.1E+16 11 187 781 +241.75 27.562° 0.1673 1974 Himalia
11 VI Himalia IPA: [haɪˈmeɪ.li.ə] 170 6.7E+18 11 451 971 +250.37 30.486° 0.1513 1904
12 X Lysithea IPA: [laɪˈsɪθ.i.ə] 36 6.3E+16 11 740 560 +259.89 27.006° 0.1322 1938
13 VII Elara IPA: [ˈɛl.ə.rə] 86 8.7E+17 11 778 034 +261.14 29.691° 0.1948 1905
14 S/2000 J 11 4 9.0E+13 12 570 424 +287.93 27.584° 0.2058 2001
15 XLVI Carpo IPA: [ˈkɑr.poʊ] 3 4.5E+13 17 144 873 +458.62 56.001° 0.2735 2003 Carpo
16 S/2003 J 12 1 1.5E+12 17 739 539 -482.69 142.680° 0.4449 2003 ?
17 XXXIV Euporie IPA: [jʊˈpɔr.i.ə] 2 1.5E+13 19 088 434 -538.78 144.694° 0.0960 2002 Ananke
18 S/2003 J 3 2 1.5E+13 19 621 780 -561.52 146.363° 0.2507 2003
19 S/2003 J 18 2 1.5E+13 19 812 577 -569.73 147.401° 0.1569 2003
20 XLII Thelxinoe IPA: [θɛlkˈsɪ.noʊ.i] 2 1.5E+13 20 453 753 -597.61 151.292° 0.2684 2004
21 XXXIII Euanthe IPA: [jʊˈæn.θi] 3 4.5E+13 20 464 854 -598.09 143.409° 0.2000 2002
22 XLV Helike IPA: [ˈhɛl.ɨ.ki] 4 9.0E+13 20 540 266 -601.40 154.586° 0.1374 2003
23 XXXV Orthosie IPA: [ɔrˈθoʊ.zi.ə] 2 1.5E+13 20 567 971 -602.62 142.366° 0.2433 2002
24 XXIV Iocaste IPA: [ˌaɪ.əˈkæs.ti] 5 1.9E+14 20 722 566 -609.43 147.248° 0.2874 2001
25 S/2003 J 16 2 1.5E+13 20 743 779 -610.36 150.769° 0.3184 2003
26 XXVII Praxidike IPA: [prækˈsɪd.ɨ.ki] 7 4.3E+14 20 823 948 -613.90 144.205° 0.1840 2001
27 XXII Harpalyke IPA: [hɑrˈpæl.ɨ.ki] 4 1.2E+14 21 063 814 -624.54 147.223° 0.2440 2001
28 XL Mneme IPA: [ˈni.mi] 2 1.5E+13 21 129 786 -627.48 149.732° 0.3169 2003
29 XXX Hermippe IPA: [hɝˈmɪp.i] 4 9.0E+13 21 182 086 -629.81 151.242° 0.2290 2002 Ananke?
30 XXIX Thyone IPA: [θaɪˈoʊ.ni] 4 9.0E+13 21 405 570 -639.80 147.276° 0.2525 2002 Ananke
31 XII Ananke IPA: [əˈnæŋ.ki] 28 3.0E+16 21 454 952 -642.02 151.564° 0.3445 1951
32 S/2003 J 17 2 1.5E+13 22 134 306 -672.75 162.490° 0.2379 2003 Carme
33 XXXI Aitne IPA: [ˈeɪt.ni] 3 4.5E+13 22 285 161 -679.64 165.562° 0.3927 2002
34 XXXVII Kale IPA: [ˈkeɪ.li] 2 1.5E+13 22 409 207 -685.32 165.378° 0.2011 2002
35 XX Taygete IPA: [teɪˈɪdʒ.ə.ti] 5 1.6E+14 22 438 648 -686.67 164.890° 0.3678 2001
36 S/2003 J 19 2 1.5E+13 22 709 061 -699.12 164.727° 0.1961 2003
37 XXI Chaldene IPA: [kælˈdi.ni] 4 7.5E+13 22 713 444 -699.33 167.070° 0.2916 2001
38 S/2003 J 15 2 1.5E+13 22 720 999 -699.68 141.812° 0.0932 2003 Ananke?
39 S/2003 J 10 2 1.5E+13 22 730 813 -700.13 163.813° 0.3438 2003 Carme?
40 S/2003 J 23 2 1.5E+13 22 739 654 -700.54 148.849° 0.3930 2004 Pasiphaë
41 XXV Erinome IPA: [ɛˈrɪn.ə.mi] 3 4.5E+13 22 986 266 -711.96 163.737° 0.2552 2001 Carme
42 XLI Aoede IPA: [eɪˈi.di] 4 9.0E+13 23 044 175 -714.66 160.482° 0.6011 2003 Pasiphaë
43 XLIV Kallichore IPA: [kəˈlɪk.ə.ri] 2 1.5E+13 23 111 823 -717.81 164.605° 0.2041 2003 Carme?
44 XXIII Kalyke IPA: [ˈkæl.ɨ.ki] 5 1.9E+14 23 180 773 -721.02 165.505° 0.2139 2001 Carme
45 XI Carme IPA: [ˈkɑr.mi] 46 1.3E+17 23 197 992 -721.82 165.047° 0.2342 1938
46 XVII Callirrhoe IPA: [kəˈlɪr.oʊ.i] 9 8.7E+14 23 214 986 -722.62 139.849° 0.2582 2000 Pasiphaë
47 XXXII Eurydome IPA: [jʊˈrɪd.ə.mi] 3 4.5E+13 23 230 858 -723.36 149.324° 0.3769 2002 Pasiphaë?
48 XXXVIII Pasithee IPA: [pəˈsɪθ.i.ə] 2 1.5E+13 23 307 318 -726.93 165.759° 0.3288 2002 Carme
49 XLVIII Cyllene IPA: [sɨˈli.ni] 2 1.5E+13 23 396 269 -731.10 140.148° 0.4115 2003 Pasiphaë
50 XLVII Eukelade IPA: [jʊˈkɛl.ə.di] 4 9.0E+13 23 483 694 -735.20 163.996° 0.2828 2003 Carme
51 S/2003 J 4 2 1.5E+13 23 570 790 -739.29 147.175° 0.3003 2003 Pasiphaë
52 VIII Pasiphaë IPA: [pəˈsɪf.ə.i] 60 3.0E+17 23 609 042 -741.09 141.803° 0.3743 1908
53 XXXIX Hegemone IPA: [həˈdʒɛm.ə.ni] 3 4.5E+13 23 702 511 -745.50 152.506° 0.4077 2003
54 XLIII Arche IPA: [ˈɑr.ki] 3 4.5E+13 23 717 051 -746.19 164.587° 0.1492 2002 Carme
55 XXVI Isonoe IPA: [aɪˈsɑn.oʊ.i] 4 7.5E+13 23 800 647 -750.13 165.127° 0.1775 2001
56 S/2003 J 9 1 1.5E+12 23 857 808 -752.84 164.980° 0.2761 2003
57 S/2003 J 5 4 9.0E+13 23 973 926 -758.34 165.549° 0.3070 2003
58 IX Sinope IPA: [sɨˈnoʊ.pi] 38 7.5E+16 24 057 865 -762.33 153.778° 0.2750 1914 Pasiphaë
59 XXXVI Sponde IPA: [ˈspɑn.di] 2 1.5E+13 24 252 627 -771.60 154.372° 0.4431 2002
60 XXVIII Autonoe IPA: [ɔˈtɑn.oʊ.i] 4 9.0E+13 24 264 445 -772.17 151.058° 0.3690 2002
61 XLIX Kore IPA: [ˈkɔr.i] 2 1.5E+13 23 345 093 -776.02 137.371° 0.1951 2003
62 XIX Megaclite IPA: [ˌmɛg.əˈklaɪ.ti] 5 2.1E+14 24 687 239 -792.44 150.398° 0.3077 2001
63 S/2003 J 2 2 1.5E+13 30 290 846 -1077.02 153.521° 0.1882 2003 ?
  • (1) Computed using the IAU-MPC Satellites Ephemeris Service µ value
  • (2) Source: JPL/NASA
  • (3) Source (for Themisto outward): IAU-MPC Satellites Ephemeris Service
  • (4) Periods with negative values are retrograde.
  • (5) Computed from IAG Travaux 2001 for Metis through Callisto, showing inclination to Jupiter's equator; taken from IAU-MPC Satellites Ephemeris Service orbital elements for the others, using inclination to the local Laplace plane.

Grouping the moons

As for all four giant planets, the Jupiter's satellites are categorised into two main categories:

  • Regular satellites consisting of the Amalthea group of inner moons and the four Galilean moons, formed in situ
  • Irregular satellites, far-reaching, highly eccentrical, substantially smaller objects generally picked up on Jupiter's space journey
Irregular satellites of Jupiter.

The first diagram illustrates the orbits of the irregular satellites of Jupiter discovered so far. The eccentricity of the orbits is represented by the 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 (~53 Gm for Jupiter). The following diagram shows separately the distribution of inclination versus eccentricity for the retrograde satellites, facilitating the identification of the groupings.

Prograde irregular moons

Himalia group is "tight", spread over barely 1.4 Gm in semi-major axis and 1.6° in inclination (27.5 ± 0.8°). The eccentricities vary between 0.11 and 0.25.

Themisto and Carpo are isolated in space.

Retrograde irregular moons

Retrograde satellites: inclinations (°) vs eccentricities with Carme's (orange) and Ananke's (yellow) groups identified.

What is left of the outer retrograde irregular satellites of Jupiter can be grouped into three families, based on shared orbital characteristics and bearing the name of the largest member in each case. These families are clumps in semi-major axis, but also in inclination and in eccentricity.

Carme's group is obvious, centered on a = 23 404 Mm; i = 165.2±0.3° and e = 0.238–0.272. Only S/2003 J 10 seems somewhat apart, because of its great eccentricity.

Ananke's group is centered on a = 21 276 Mm; i = 149.0±0.5° and e = 0.216–0.244; but its borders are less definite. The eight core members (S/2003 J 16, Mneme, Euanthe, Orthosie, Harpalyke, Praxidike, Thyone, Thelxinoe, Ananke, Iocaste) are well-clumped, but the attribution of the remaining eight members to the group is debatable to varying degrees.

Pasiphaë's group, finally, picks up the remainder, with the exception of the moons at the inner and outer limits of the groups (S/2003 J 12 and S/2003 J 2); it is centered on a = 23 624 Mm; i = 151.4±6.9° and e = 0.156–0.432 (note the much larger spreads). If it is real, it must be ancient to explain the dispersion of its membership.

S/2003 J 12, and S/2003 J 2, the most exterior moon, are again isolated.

Naming notes

Some asteroids share the same names as moons of Jupiter: 9 Metis, 38 Leda, 52 Europa, 85 Io, 113 Amalthea, 239 Adrastea.

A couple of asteroids shared the names of Jovian moons until spelling differences were made permanent by the IAU. Those contrasting pairs are the moon Ganymede and the asteroid 1036 Ganymed; and the moon Callisto and the asteroid 204 Kallisto. See also Name conflicts of solar system objects.

Note that the satellites discovered between 1904 and 1951 (Himalia, Elara, Pasiphaë, Sinope, Lysithea, Carme and Ananke) were not officially named until 1975, 24 years after the last satellite was discovered. They were simply known by their Roman numeral designations (Jupiter VI through Jupiter XII).

See Naming of natural satellites

See also

Notes

References


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