Moons of Jupiter

There are 79 known moons of Jupiter, not counting a number of moonlets likely shed from the inner moons, and S/2003 J 24, whose orbital elements have not yet been published.[1][2][3] All together, they form a satellite system which is called the Jovian system. The most massive of the moons are the four Galilean moons: Io; Europa; Ganymede; and Callisto, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. Much more recently, beginning in 1892, dozens of far smaller Jovian moons have been detected and have received the names of lovers (or other sexual partners) or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 75 known moons and the rings together composing just 0.003% of the total orbiting mass.

A montage of Jupiter and its four largest moons (distance and sizes not to scale)

Of Jupiter's moons, eight are regular satellites with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter's equatorial plane. The Galilean satellites are nearly spherical in shape due to their planetary mass, and so would be considered at least dwarf planets if they were in direct orbit around the Sun. The other four regular satellites are much smaller and closer to Jupiter; these serve as sources of the dust that makes up Jupiter's rings. The remainder of Jupiter's moons are irregular satellites whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were probably captured by Jupiter from solar orbits. Twenty-two of the irregular satellites have not yet been officially named.

CharacteristicsEdit

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

The physical and orbital characteristics of the moons vary widely. The four Galileans are all over 3,100 kilometres (1,900 mi) in diameter; the largest Galilean, Ganymede, is the ninth largest object in the Solar System, after the Sun and seven of the planets, Ganymede being larger than Mercury. All other Jovian moons are less than 250 kilometres (160 mi) in diameter, with most barely exceeding 5 kilometres (3.1 mi).[note 1] Their orbital shapes range from nearly perfectly circular to highly eccentric and inclined, and many revolve in the direction opposite to Jupiter's rotation (retrograde motion). Orbital periods range from seven hours (taking less time than Jupiter does to rotate around its axis), to some three thousand times more (almost three Earth years).

Origin and evolutionEdit

 
The relative masses of the Jovian moons. Those smaller than Europa are not visible at this scale, and combined would only be visible at 100× magnification.

Jupiter's regular satellites are believed to have formed from a circumplanetary disk, a ring of accreting gas and solid debris analogous to a protoplanetary disk.[4][5] They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history.[4][6]

Simulations suggest that, while the disk had a relatively high mass at any given moment, over time a substantial fraction (several tens of a percent) of the mass of Jupiter captured from the solar nebula was passed through it. However, only 2% of the proto-disk mass of Jupiter is required to explain the existing satellites.[4] Thus, several generations of Galilean-mass satellites may have been in Jupiter's early history. Each generation of moons might have spiraled into Jupiter, because of drag from the disk, with new moons then forming from the new debris captured from the solar nebula.[4] By the time the present (possibly fifth) generation formed, the disk had thinned so that it no longer greatly interfered with the moons' orbits.[6] The current Galilean moons were still affected, falling into and being partially protected by an orbital resonance with each other, which still exists for Io, Europa, and Ganymede. Ganymede's larger mass means that it would have migrated inward at a faster rate than Europa or Io.[4]

The outer, irregular moons are thought to have originated from captured asteroids, whereas the protolunar disk was still massive enough to absorb much of their momentum and thus capture them into orbit. Many are believed to have broken up by mechanical stresses during capture, or afterward by collisions with other small bodies, producing the moons we see today.[7]


DiscoveryEdit

 
Jupiter and the Galilean moons through a 25 cm (10 in) Meade LX200 telescope.
 
The number of moons known for each of the four outer planets up to October 2019. Jupiter currently has 79 known satellites.

Chinese historian Xi Zezong claimed that the earliest record of a Jovian moon (Ganymede or Callisto) was a note by Chinese astronomer Gan De of an observation around 364 BC regarding a "reddish star".[8] However, the first certain observations of Jupiter's satellites were those of Galileo Galilei in 1609.[9] By January 1610, he had sighted the four massive Galilean moons with his 20× magnification telescope, and he published his results in March 1610.[10]

Simon Marius had independently discovered the moons one day after Galileo, although he did not publish his book on the subject until 1614. Even so, the names Marius assigned are used today: Ganymede, Callisto, Io, and Europa.[11] No additional satellites were discovered until E. E. Barnard observed Amalthea in 1892.[12]

With the aid of telescopic photography, further discoveries followed quickly over the course of the 20th century. Himalia was discovered in 1904,[13] Elara in 1905,[14] Pasiphae in 1908,[15] Sinope in 1914,[16] Lysithea and Carme in 1938,[17] Ananke in 1951,[18] and Leda in 1974.[19] By the time that the Voyager space probes reached Jupiter, around 1979, 13 moons had been discovered, not including Themisto, which had been observed in 1975,[20] but was lost until 2000 due to insufficient initial observation data. The Voyager spacecraft discovered an additional three inner moons in 1979: Metis, Adrastea, and Thebe.[21]

No additional moons were discovered for two decades, but between October 1999 and February 2003, researchers found another 34 moons using sensitive ground-based detectors.[22] These are tiny moons, in long, eccentric, generally retrograde orbits, and averaging 3 km (1.9 mi) in diameter, with the largest being just 9 km (5.6 mi) across. All of these moons are thought to have been captured asteroidal or perhaps comet bodies, possibly fragmented into several pieces.[23][24]

By 2015, a total of 15 additional moons were discovered.[24] Two more were discovered in 2016 by the team led by Scott S. Sheppard at the Carnegie Institution for Science, bringing the total to 69.[25] On 17 July 2018, the International Astronomical Union confirmed that Sheppard's team had discovered ten more moons around Jupiter, bringing the total number to 79.[2] Among these is Valetudo, which has a prograde orbit, but crosses paths with several moons that have retrograde orbits, making an eventual collision—at some point on a billions-of-years timescale—likely.[2]

In September 2020, researchers from the University of British Columbia identified 45 candidate moons from an analysis of archival images taken in 2010 by the Canada-France-Hawaii Telescope.[26] These candidates were mainly small and faint, down to a magnitude of 25.7 or over 800 m (0.50 mi) in diameter. From the number of candidate moons detected within a sky area of one square degree, the team extrapolated that the population of retrograde Jovian moons brighter than magnitude 25.7 is around 600, within a factor of 2.[27] Although the team considers their characterised candidates to be likely moons of Jupiter, they all remain unconfirmed due to their insufficient observation data for determining reliable orbits for each of them.[26]

NamingEdit

 
Galilean moons around Jupiter   Jupiter ·   Io ·   Europa ·   Ganymede ·   Callisto
 
Orbits of Jupiter's inner moons within its rings

The Galilean moons of Jupiter (Io, Europa, Ganymede, and Callisto) were named by Simon Marius soon after their discovery in 1610.[28] However, these names fell out of favor until the 20th century. The astronomical literature instead simply referred to "Jupiter I", "Jupiter II", etc., or "the first satellite of Jupiter", "Jupiter's second satellite", and so on.[28] The names Io, Europa, Ganymede, and Callisto became popular in the mid-20th century,[29] whereas the rest of the moons remained unnamed and were usually numbered in Roman numerals V (5) to XII (12).[30][31] Jupiter V was discovered in 1892 and given the name Amalthea by a popular though unofficial convention, a name first used by French astronomer Camille Flammarion.[22][32]

The other moons were simply labeled by their Roman numeral (e.g. Jupiter IX) in the majority of astronomical literature until the 1970s.[33] Several different suggestions were made for names of Jupiter's outer satellites, but none were universally accepted until 1975 when the International Astronomical Union's (IAU) Task Group for Outer Solar System Nomenclature granted names to satellites V–XIII,[34] and provided for a formal naming process for future satellites still to be discovered.[34] The practice was to name newly discovered moons of Jupiter after lovers and favorites of the god Jupiter (Zeus) and, since 2004, also after their descendants.[22] All of Jupiter's satellites from XXXIV (Euporie) onward are named after descendants of Jupiter or Zeus,[22] except LIII (Dia), named after a lover of Jupiter. Names ending with "a" or "o" are used for prograde irregular satellites (the latter for highly inclined satellites), and names ending with "e" are used for retrograde irregulars.[35] With the discovery of smaller, kilometre-sized moons around Jupiter, the IAU has established an additional convention to limit the naming of small moons with absolute magnitudes greater than 18 or diameters smaller than 1 km (0.62 mi).[36] Some of the most recently confirmed moons have not received names.

Some asteroids share the same names as moons of Jupiter: 9 Metis, 38 Leda, 52 Europa, 85 Io, 113 Amalthea, 239 Adrastea. Two more asteroids previously shared the names of Jovian moons until spelling differences were made permanent by the IAU: Ganymede and asteroid 1036 Ganymed; and Callisto and asteroid 204 Kallisto.

GroupsEdit

 
The orbits of Jupiter's irregular satellites, and how they cluster into groups: by semi-major axis (the horizontal axis in Gm); by orbital inclination (the vertical axis); and orbital eccentricity (the yellow lines). The relative sizes are indicated by the circles.

Regular satellitesEdit

These have prograde and nearly circular orbits of low inclination and are split into two groups:

  • Inner satellites or Amalthea group: Metis, Adrastea, Amalthea, and Thebe. These orbit very close to Jupiter; the innermost two orbit in less than a Jovian day. The latter two are respectively the fifth and seventh largest moons in the Jovian system. Observations suggest that at least the largest member, Amalthea, did not form on its present orbit, but farther from the planet, or that it is a captured Solar System body.[37] These moons, along with a number of seen and as-yet-unseen inner moonlets (see Amalthea moonlets), replenish and maintain Jupiter's faint ring system. Metis and Adrastea help to maintain Jupiter's main ring, whereas Amalthea and Thebe each maintain their own faint outer rings.[38][39]
  • Main group or Galilean moons: Io, Europa, Ganymede and Callisto. They are some of the largest objects in the Solar System outside the Sun and the eight planets in terms of mass and are larger than any known dwarf planet. Ganymede exceeds (and Callisto nearly equals) even the planet Mercury in diameter, though they are less massive. They are respectively the fourth-, sixth-, first-, and third-largest natural satellites in the Solar System, containing approximately 99.997% of the total mass in orbit around Jupiter, while Jupiter is almost 5,000 times more massive than the Galilean moons.[note 2] The inner moons are in a 1:2:4 orbital resonance. Models suggest that they formed by slow accretion in the low-density Jovian subnebula—a disc of the gas and dust that existed around Jupiter after its formation—which lasted up to 10 million years in the case of Callisto.[40] Several are suspected of having subsurface oceans.

Irregular satellitesEdit

 
Orbits and positions of Jupiter's irregular satellites as of 1 January 2021. Prograde orbits are colored blue while retrograde orbits are colored red.
 
Inclinations (°) vs. eccentricities of Jupiter's irregular satellites, with the major groups identified. Data as of 2021.

The irregular satellites are substantially smaller objects with more distant and eccentric orbits. They form families with shared similarities in orbit (semi-major axis, inclination, eccentricity) and composition; it is believed that these are at least partially collisional families that were created when larger (but still small) parent bodies were shattered by impacts from asteroids captured by Jupiter's gravitational field. These families bear the names of their largest members. The identification of satellite families is tentative, but the following are typically listed:[1][41][42]

  • Prograde satellites:
    • Themisto is the innermost irregular moon and is not part of a known family.[1][41]
    • The Himalia group is spread over barely 1.4 Gm in semi-major axes, 1.6° in inclination (27.5 ± 0.8°), and eccentricities between 0.11 and 0.25. It has been suggested that the group could be a remnant of the break-up of an asteroid from the asteroid belt.[41]
    • Carpo is another prograde moon and is not part of a known family. It has the highest inclination of all of the prograde moons.[1]
    • Valetudo is the outermost prograde moon and is not part of a known family. Its prograde orbit crosses paths with several moons that have retrograde orbits and may in the future collide with them.[2]
  • Retrograde satellites:
    • The Carme group is spread over only 1.2 Gm in semi-major axis, 1.6° in inclination (165.7 ± 0.8°), and eccentricities between 0.23 and 0.27. It is very homogeneous in color (light red) and is believed to have originated from a D-type asteroid progenitor, possibly a Jupiter trojan.[23]
    • The Ananke group has a relatively wider spread than the previous groups, over 2.4 Gm in semi-major axis, 8.1° in inclination (between 145.7° and 154.8°), and eccentricities between 0.02 and 0.28. Most of the members appear gray, and are believed to have formed from the breakup of a captured asteroid.[23]
    • The Pasiphae group is quite dispersed, with a spread over 1.3 Gm, inclinations between 144.5° and 158.3°, and eccentricities between 0.25 and 0.43.[23] The colors also vary significantly, from red to grey, which might be the result of multiple collisions. Sinope, sometimes included in the Pasiphae group,[23] is red and, given the difference in inclination, it could have been captured independently;[41] Pasiphae and Sinope are also trapped in secular resonances with Jupiter.[43]

ListEdit

The moons of Jupiter are listed below by orbital period. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in bold. These are the four Galilean moons, which are comparable in size to the Moon. The other moons are much smaller, with the least massive Galilean moon being more than 7,000 times more massive than the most massive of the other moons. The irregular captured moons are shaded light gray when prograde and dark gray when retrograde. The orbits and mean distances of the irregular moons are strongly variable over short timescales due to frequent planetary and solar perturbations,[44] therefore the epochs of all orbital elements listed are based on the Julian date of 2459200.5, or 17 December 2020.[45] As of 2021, S/2003 J 10 is the only moon of Jupiter considered lost due to its uncertain orbit.[46] A number of other moons have only been observed for a year or two, but have decent enough orbits to be easily measurable at present.[44]

Key
 
Inner moons

Galilean moons

Ungrouped moons

Himalia group

Ananke group

Carme group

Pasiphae group
Order
[note 3]
Label
[note 4]
Name
Pronunciation Image Abs.
magn.
Diameter (km)[note 5] Mass
(×1016 kg)
Semi-major axis
(km)[47]
Orbital period (d)
[47][note 6]
Inclination
(°)[47]
Eccentricity
[1]
Discovery
year
[22]
Discoverer[22] Group
[note 7]
1 XVI Metis /ˈmtɪs/ 10.5 43
(60 × 40 × 34)
≈ 3.6 128852 +0.2988
(+7h 10m 16s)
2.226 0.0077 1979 Synnott
(Voyager 1)
Inner
2 XV Adrastea /ædrəˈstə/ 12.0 16.4
(20 × 16 × 14)
≈ 0.2 129000 +0.3023
(+7h 15m 21s)
2.217 0.0063 1979 Jewitt
(Voyager 2)
Inner
3 V Amalthea /æməlˈθə/[48] 7.1 167
(250 × 146 × 128)
208 181366 +0.5012
(+12h 01m 46s)
2.565 0.0075 1892 Barnard Inner
4 XIV Thebe /ˈθb/ 9.0 98.6
(116 × 98 × 84)
≈ 43 222452 +0.6778
(+16h 16m 02s)
2.909 0.0180 1979 Synnott
(Voyager 1)
Inner
5 I Io /ˈ/ −1.7 3643.2
(3660 × 3637 × 3631)
8931900 421700 +1.7691 0.050[49] 0.0041 1610 Galilei Galilean
6 II Europa /jʊəˈrpə/[50] −1.4 3121.6 4800000 671034 +3.5512 0.471[49] 0.0094 1610 Galilei Galilean
7 III Ganymede /ˈɡænɪmd/[51][52] −2.1 5268.2 14819000 1070412 +7.1546 0.204[49] 0.0011 1610 Galilei Galilean
8 IV Callisto /kəˈlɪst/ −1.2 4820.6 10759000 1882709 +16.689 0.205[49] 0.0074 1610 Galilei Galilean
9 XVIII Themisto /θɪˈmɪst/ 12.9 9 ≈ 0.069 7405000 +130.18 44.590 0.2514 1975/2000 Kowal & Roemer/
Sheppard et al.
Themisto
10 XIII Leda /ˈldə/ 12.7 21.5 ≈ 0.6 11196000 +242.02 27.641 0.1648 1974 Kowal Himalia
11 LXXI Ersa /ˈɜːrsə/ 15.9 3 ≈ 0.0045 11348700 +246.99 31.028 0.1043 2018 Sheppard et al. Himalia
12 LXV Pandia /pænˈdə/ 16.2 3 ≈ 0.0045 11462300 +250.71 27.023 0.2084 2017 Sheppard et al. Himalia
13 VI Himalia /hɪˈmliə/ 7.9 139.6
(150 × 120)
420 11497400 +251.86 30.214 0.1510 1904 Perrine Himalia
14 X Lysithea /lˈsɪθiə/ 11.2 42.2 ≈ 6.3 11628300 +256.17 27.015 0.1377 1938 Nicholson Himalia
15 VII Elara /ˈɛlərə/ 9.6 79.9 ≈ 87 11671600 +257.60 30.216 0.2079 1905 Perrine Himalia
16 LIII Dia /ˈdə/ 16.3 4 ≈ 0.009 12304900 +278.85 27.481 0.2606 2000 Sheppard et al. Himalia
17 XLVI Carpo /ˈkɑːrp/ 16.1 3 ≈ 0.0045 17151800 +458.90 50.138 0.4967 2003 Sheppard et al. Carpo
18 LXII Valetudo /vælɪˈtjd/ 17.0 1 ≈ 0.00015 18819000 +527.41 32.033 0.2018 2016 Sheppard et al. Valetudo
19 XXXIV Euporie /ˈjpər/ 16.3 2 ≈ 0.0015 19593900 −560.32 147.851 0.1402 2001 Sheppard et al. Ananke
20 LX Eupheme /jˈfm/ 16.6 2 ≈ 0.0015 20126300 −583.31 150.042 0.4104 2003 Sheppard et al. Ananke
21 LV S/2003 J 18 16.5 2 ≈ 0.0015 20348800 −593.01 142.783 0.0465 2003 Gladman et al. Ananke
22 LII S/2010 J 2 17.3 1 ≈ 0.00015 20436700 −596.86 148.697 0.3403 2010 Veillet Ananke
23 XLV Helike /ˈhɛlɪk/ 16.0 4 ≈ 0.009 20479500 −598.74 155.067 0.1331 2003 Sheppard et al. Ananke
24   S/2003 J 16 16.3 2 ≈ 0.0015 20512500 −600.18 151.163 0.3331 2003 Gladman et al. Ananke
25   S/2003 J 2 16.7 2 ≈ 0.0015 20554400 −602.02 149.204 0.2777 2003 Sheppard et al. Ananke
26 XXXIII Euanthe /jˈænθ/ 16.4 3 ≈ 0.0045 20583300 −603.29 146.808 0.1096 2001 Sheppard et al. Ananke
27 LXVIII S/2017 J 7 16.6 2 ≈ 0.0015 20600100 −604.03 146.739 0.2626 2017 Sheppard et al. Ananke
28 XXX Hermippe /hərˈmɪp/ 15.6 4 ≈ 0.009 20666200 −606.94 146.753 0.1981 2001 Sheppard et al. Ananke
29 XXVII Praxidike /prækˈsɪdɪk/ 14.9 7 ≈ 0.043 20682900 −607.68 149.692 0.2959 2000 Sheppard et al. Ananke
30 XXIX Thyone /θˈn/ 15.8 4 ≈ 0.009 20712800 −609.00 147.328 0.1770 2001 Sheppard et al. Ananke
31 XLII Thelxinoe /θɛlkˈsɪn/ 16.3 2 ≈ 0.0015 20893300 −616.97 146.916 0.1709 2003 Sheppard et al. Ananke
32 LXIV S/2017 J 3 16.5 2 ≈ 0.0015 20976900 −620.68 147.968 0.1907 2017 Sheppard et al. Ananke
33 XII Ananke /əˈnæŋk/ 11.7 29.1 ≈ 3.0 21042500 −623.59 148.675 0.1747 1951 Nicholson Ananke
34 XL Mneme /ˈnm/ 16.3 2 ≈ 0.0015 21064100 −624.55 151.087 0.3428 2003 Gladman et al. Ananke
35 LIV S/2016 J 1 16.8 1 ≈ 0.00015 21154000 −628.56 143.824 0.1294 2016 Sheppard et al. Ananke
36 XXXV Orthosie /ɔːrˈθz/ 16.7 2 ≈ 0.0015 21171000 −629.31 148.488 0.4838 2001 Sheppard et al. Ananke
37 XXII Harpalyke /hɑːrˈpælɪk/ 15.9 4 ≈ 0.009 21280200 −634.19 148.298 0.1602 2000 Sheppard et al. Ananke
38 XXIV Iocaste /əˈkæst/ 15.4 5 ≈ 0.019 21431800 −640.98 149.424 0.3295 2000 Sheppard et al. Ananke
39 LXX S/2017 J 9 16.1 3 ≈ 0.0045 21492900 −643.72 155.775 0.2524 2017 Sheppard et al. Ananke
40   S/2003 J 12 17.0 1 ≈ 0.00015 21557700 −646.64 154.690 0.3657 2003 Sheppard et al. Ananke
41   S/2003 J 4 16.7 2 ≈ 0.0015 22048600 −668.85 149.401 0.4967 2003 Sheppard et al. Pasiphae
42 XXV Erinome /ɛˈrɪnəm/ (?) 16.0 3 ≈ 0.0045 22354300 −682.80 164.821 0.2052 2000 Sheppard et al. Carme
43 XXXI Aitne /ˈtn/ 16.0 3 ≈ 0.0045 22386500 −684.28 166.238 0.3150 2001 Sheppard et al. Carme
44 L Herse /ˈhɜːrs/ 16.5 2 ≈ 0.0015 22408800 −685.30 164.347 0.1854 2003 Gladman et al. Carme
45 XX Taygete /tˈɪɪt/ 15.5 5 ≈ 0.016 22433500 −686.44 163.261 0.3257 2000 Sheppard et al. Carme
46 LXIII S/2017 J 2 16.4 2 ≈ 0.0015 22472900 −688.25 165.676 0.3852 2017 Sheppard et al. Carme
47 LXVII S/2017 J 6 16.4 2 ≈ 0.0015 22543800 −691.51 155.185 0.3226 2017 Sheppard et al. Pasiphae
48 XLVII Eukelade /jˈkɛləd/ 15.9 4 ≈ 0.009 22576700 −693.02 163.822 0.2790 2003 Sheppard et al. Carme
49 XI Carme /ˈkɑːrm/ 10.6 46.7 ≈ 13 22579900 −693.17 163.535 0.2295 1938 Nicholson Carme
50 LXI S/2003 J 19 16.6 2 ≈ 0.0015 22752500 −701.13 167.738 0.2928 2003 Gladman et al. Carme
51 XXVI Isonoe /ˈsɒn/ 16.0 4 ≈ 0.009 22776700 −702.25 162.834 0.2159 2000 Sheppard et al. Carme
52 (lost) S/2003 J 10 16.8 2 ≈ 0.0015 22896200 −707.78 163.481 0.2066 2003 Sheppard et al. Carme?
53 XXVIII Autonoe /ɔːˈtɒn/ 15.5 4 ≈ 0.009 22933400 −709.51 148.145 0.4290 2001 Sheppard et al. Pasiphae
54 LVIII Philophrosyne /fɪləˈfrɒzɪn/ 16.7 2 ≈ 0.0015 22939900 −709.81 147.900 0.3013 2003 Sheppard et al. Pasiphae
55 XLVIII Cyllene /sɪˈln/ 16.3 2 ≈ 0.0015 22965200 −710.99 150.047 0.6079 2003 Sheppard et al. Pasiphae
56 XXXVIII Pasithee /ˈpæsɪθ/ 16.8 2 ≈ 0.0015 22967800 −711.11 164.727 0.2097 2001 Sheppard et al. Carme
57 LI S/2010 J 1 16.4 2 ≈ 0.0015 22986900 −712.00 164.559 0.2937 2010 Jacobson et al. Carme
58 VIII Pasiphae /pəˈsɪf/ 10.1 57.8 ≈ 30 23119300 −718.16 151.998 0.4362 1908 Melotte Pasiphae
59 XXXVI Sponde /ˈspɒnd/ 16.7 2 ≈ 0.0015 23146500 −719.42 144.563 0.3455 2001 Sheppard et al. Pasiphae
60 LXIX S/2017 J 8 17.0 1 ≈ 0.00015 23173700 −720.69 166.071 0.2039 2017 Sheppard et al. Carme
61 XXXII Eurydome /jʊəˈrɪdəm/ 16.2 3 ≈ 0.0045 23214500 −722.59 150.289 0.2975 2001 Sheppard et al. Pasiphae
62 LXVI S/2017 J 5 16.5 2 ≈ 0.0015 23352500 −729.05 166.555 0.2460 2017 Sheppard et al. Carme
63 XXIII Kalyke /ˈkælɪk/ 15.4 6.9 ≈ 0.04 23377400 −730.21 166.899 0.2660 2000 Sheppard et al. Carme
64 XXXIX Hegemone /hɪˈɛmən/ 15.9 3 ≈ 0.0045 23422300 −732.32 154.675 0.3358 2003 Sheppard et al. Pasiphae
65 XXXVII Kale /ˈkl/ 16.4 2 ≈ 0.0015 23512200 −736.54 166.177 0.2893 2001 Sheppard et al. Carme
66 XLIV Kallichore /kəˈlɪkər/ 16.4 2 ≈ 0.0015 23552900 −738.45 167.727 0.3183 2003 Sheppard et al. Carme
67 LXXII S/2011 J 1 16.7 2 ≈ 0.0015 23714400 −746.06 164.799 0.3193 2011 Sheppard et al. Carme
68 LIX S/2017 J 1 16.6 2 ≈ 0.0015 23753600 −747.91 147.253 0.4500 2017 Sheppard et al. Pasiphae
69 XXI Chaldene /kælˈdn/ 16.0 4 ≈ 0.009 23848300 −752.39 162.749 0.2705 2000 Sheppard et al. Carme
70 XLIII Arche /ˈɑːrk/ 16.2 3 ≈ 0.0045 23926500 −756.09 166.408 0.2367 2002 Sheppard et al. Carme
71 LVII Eirene /ˈrn/ 15.8 4 ≈ 0.009 23934500 −756.47 162.713 0.2413 2003 Sheppard et al. Carme
72 XLIX Kore /ˈkɔːr/ 16.6 2 ≈ 0.0015 23999700 −759.56 136.628 0.2347 2003 Sheppard et al. Pasiphae
73 LVI S/2011 J 2 16.8 1 ≈ 0.00015 24114700 −765.03 152.125 0.1729 2011 Sheppard et al. Pasiphae
74   S/2003 J 9 16.9 1 ≈ 0.00015 24168700 −767.60 166.334 0.1702 2003 Sheppard et al. Carme
75 XIX Megaclite /ˌmɛɡəˈklt/ 15.0 5 ≈ 0.021 24212300 −769.68 145.574 0.3139 2000 Sheppard et al. Pasiphae
76 XLI Aoede /ˈd/ 15.6 4 ≈ 0.009 24283000 −773.05 151.908 0.3131 2003 Sheppard et al. Pasiphae
77   S/2003 J 23 16.6 2 ≈ 0.0015 24678200 −792.00 146.155 0.3208 2003 Sheppard et al. Pasiphae
78 XVII Callirrhoe /kəˈlɪr/ 13.9 9.6 ≈ 0.087 24692400 −792.69 149.792 0.3562 1999 Scotti et al. Pasiphae
79 IX Sinope /sɪˈnp/ 11.1 35 ≈ 7.5 24864100 −800.97 158.597 0.1669 1914 Nicholson Pasiphae

ExplorationEdit

 
The orbit and motion of the Galilean moons around Jupiter, as captured by JunoCam aboard the Juno spacecraft.

The first spacecraft to visit Jupiter were Pioneer 10 in 1973, and Pioneer 11 a year later, taking low-resolution images of the four Galilean moons and returning data on their atmospheres and radiation belts.[53] The Voyager 1 and Voyager 2 probes visited Jupiter in 1979, discovering the volcanic activity on Io and the presence of water ice on the surface of Europa. The Cassini probe to Saturn flew by Jupiter in 2000 and collected data on interactions of the Galilean moons with Jupiter's extended atmosphere. The New Horizons spacecraft flew by Jupiter in 2007 and made improved measurements of its satellites' orbital parameters.

The Galileo spacecraft was the first to enter orbit around Jupiter, arriving in 1995 and studying it until 2003. During this period, Galileo gathered a large amount of information about the Jovian system, making close approaches to all of the Galilean moons and finding evidence for thin atmospheres on three of them, as well as the possibility of liquid water beneath the surfaces of Europa, Ganymede, and Callisto. It also discovered a magnetic field around Ganymede.

 
Ganymede taken by Juno during its 34th perijove.

In 2016, the Juno spacecraft imaged the Galilean moons from above their orbital plane as it approached Jupiter orbit insertion, creating a time-lapse movie of their motion.[54]

See alsoEdit

NotesEdit

  1. ^ For comparison, the area of a sphere with diameter 250 km is about the area of Senegal and comparable to the area of Belarus, Syria and Uruguay. The area of a sphere with a diameter of 5 km is about the area of Guernsey and somewhat more than the area of San Marino. (But note that these smaller moons are not spherical.)
  2. ^ Jupiter Mass of 1.8986 × 1027 kg / Mass of Galilean moons 3.93 × 1023 kg = 4,828
  3. ^ Order refers to the position among other moons with respect to their average distance from Jupiter.
  4. ^ Label refers to the Roman numeral attributed to each moon in order of their naming.
  5. ^ Diameters with multiple entries such as "60 × 40 × 34" reflect that the body is not a perfect spheroid and that each of its dimensions has been measured well enough.
  6. ^ Periods with negative values are retrograde.
  7. ^ "?" refers to group assignments that are not considered sure yet.

ReferencesEdit

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External linksEdit