Moons of Jupiter

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

There are 79 known moons of Jupiter.[1][2][3] This gives Jupiter the largest number of moons with reasonably stable orbits of any planet in the Solar System.[4] The most massive of the moons are the four Galilean moons, 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. From the end of the 19th century, dozens of much smaller Jovian moons have been discovered and have received the names of lovers 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 comprising just 0.003% of the total orbiting mass.

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

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-seven of the irregular satellites have not yet been officially named.

Characteristics[edit]

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 spin (retrograde motion). Orbital periods range from seven hours (taking less time than Jupiter does to spin around its axis), to some three thousand times more (almost three Earth years).

Origin and evolution[edit]

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.[5][6] They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history.[5][7]

Simulations suggest that, while the disk had a relatively high mass at any given moment, over time a substantial fraction (several tenths 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.[5] Thus there may have been several generations of Galilean-mass satellites 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.[5] By the time the present (possibly fifth) generation formed, the disk had thinned so that it no longer greatly interfered with the moons' orbits.[7] 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.[5]

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.[8]

Discovery[edit]

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

Some scholars propose that the earliest record of a Jovian moon (Ganymede or Callisto) is a note by Chinese astronomer Gan De of an observation around 364 BC.[9]

However, the first certain observations of Jupiter's satellites were those of Galileo Galilei in 1609.[10] By January 1610, he had sighted the four massive Galilean moons with his 30× magnification telescope, and he published his results in March 1610.[11]

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.[12] No additional satellites were discovered until E. E. Barnard observed Amalthea in 1892.[13]

With the aid of telescopic photography, further discoveries followed quickly over the course of the 20th century. Himalia was discovered in 1904,[14] Elara in 1905,[15] Pasiphae in 1908,[16] Sinope in 1914,[17] Lysithea and Carme in 1938,[18] Ananke in 1951,[19] and Leda in 1974.[20]

Jupiter and the Galilean moons through a 25 cm (10 in) Meade LX200 telescope.

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,[21] 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.[22]

No additional moons were discovered for two decades, generally during the 1980s and 1990s, but between October 1999 and February 2003, researchers found another 34 moons using sensitive ground-based detectors.[23] 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.[24][25]

By 2015, a total of 15 additional moons were discovered.[25] 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.[26] On 17 July 2018, the International Astronomical Union confirmed that Sheppard's team discovered ten more moons around Jupiter, bringing the total number to 79.[27][28] 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.[29]

Additional tiny moons likely exist but remain undiscovered, as they are very difficult for astronomers to detect.[4]

The number of moons known for each of the four outer planets up to July 2018. Jupiter currently has 79 known satellites.

Naming[edit]

The Galilean moons and their orbits around Jupiter.

The Galilean moons of Jupiter (Io, Europa, Ganymede, and Callisto) were named by Simon Marius soon after their discovery in 1610.[30] 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.[30] The names Io, Europa, Ganymede, and Callisto became popular in the mid-20th century,.[31] whereas the rest of the moons remained unnamed and were usually numbered in Roman numerals V (5) to XII (12).[32][better source needed] 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.[23]

The other moons were simply labeled by their Roman numeral (e.g. Jupiter IX) in the majority of astronomical literature until the 1970s.[33] In 1975, 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.[35] All of Jupiter's satellites from XXXIV (Euporie) onward are named after daughters of Jupiter or Zeus,[35] except LIII (Dia), named after a lover of Jupiter, and LXII (Valetudo), named after a great-granddaughter 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.[36] The most recently confirmed moons Jupiter LI through LXXII (with the exception of Jupiter LIII Dia and Jupiter LXII Valetudo) 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.

Groups[edit]

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 satellites[edit]

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 as-yet-unseen inner 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 even the planet Mercury in diameter. 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 satellites[edit]

Jupiter's outer moons and their highly inclined orbits

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:[41][42][43]

  • Themisto[42] is the innermost irregular moon and is not part of a known family.[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.[41]
  • Valetudo, reported 2018, is the outermost prograde moon and is not part of a known family.[41]
Retrograde satellites: inclinations (°) vs. eccentricities, with Carme's (orange) and Ananke's (yellow) groups identified
  • 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.[24]
  • 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.[24]
  • 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.[24] The colors also vary significantly, from red to grey, which might be the result of multiple collisions. Sinope, sometimes included in the Pasiphae group,[24] is red and, given the difference in inclination, it could have been captured independently;[42] Pasiphae and Sinope are also trapped in secular resonances with Jupiter.[44]

List[edit]

Key

Galilean moons

Prograde irregular moons

Retrograde moons

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 7000 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. All orbits are based on the estimated orbit on the Julian date 2457000, or 3 September 2017. As several moons of Jupiter are currently lost, these orbital elements may be only rough approximations. As of 2018, seven satellites are considered to be lost. These are S/2003 J 2, S/2003 J 4, S/2003 J 9, S/2003 J 10, S/2003 J 12, S/2003 J 16, and S/2003 J 23. A number of other moons have only been observed for a year or two, but have decent enough orbits to be easily measurable even in 2018.

Order
[note 3]
Label
[note 4]
Name
Pronunciation Image Abs.
magn.
Diameter
(km)[note 5]
Mass
(×1016 kg)
Semi-major
axis

(km)[45]
Orbital period
(d)[45][note 6]
Inclination
(°)[45]
Eccentr.
[41]
Discovery
year
[23]
Discoverer[23] Group
[note 7]
1 XVI Metis /ˈmtɪs/
Metis.jpg
10.5 60 × 40 × 34 ≈ 3.6 128852 +7h 10m 16s 2.226 0.0077 1979 Synnott
(Voyager 1)
Inner
2 XV Adrastea /əˈdræstiə/
Adrastea.jpg
12.0 20 × 16 × 14 ≈ 0.2 129000 +7h 15m 21s 2.217 0.0063 1979 Jewitt
(Voyager 2)
Inner
3 V Amalthea /əˈmælθiə/[46]
Amalthea Voyager-1.png
7.1 250 × 146 × 128
(167±4.0)
208 181366 +12h 01m 46s 2.565 0.0075 1892 Barnard Inner
4 XIV Thebe /ˈθbi/
Thebe.jpg
9.0 116 × 98 × 84 ≈ 43 222452 +16h 16m 02s 2.909 0.0180 1979 Synnott
(Voyager 1)
Inner
5 I Io /ˈ/
−1.7 3660.0
× 3637.4
× 3630.6
8931900 421700 +1.7691 0.050[47] 0.0041 1610 Galilei Galilean
6 II Europa /jʊəˈrpə/[48]
Europa-moon.jpg
−1.4 3121.6 4800000 671034 +3.5512 0.471[47] 0.0094 1610 Galilei Galilean
7 III Ganymede /ˈɡænɪmd/[49][50]
Ganymede g1 true-edit1.jpg
−2.1 5262.4 14819000 1070412 +7.1546 0.204[47] 0.0011 1610 Galilei Galilean
8 IV Callisto /kəˈlɪst/
Callisto.jpg
−1.2 4820.6 10759000 1882709 +16.689 0.205[47] 0.0074 1610 Galilei Galilean
9 XVIII Themisto /θɪˈmɪst/ S 2000 J 1.jpg 13.5 8 0.069 7393216 +129.87 45.762 0.2115 1975/2000 Kowal & Roemer/
Sheppard et al.
Themisto
10 XIII Leda /ˈldə/
Leda2(moon).jpg
12.8 16 0.6 11187781 +240.82 27.562 0.1673 1974 Kowal Himalia
11 VI Himalia /hˈmliə/
Himalia from New Horizons.jpg
8.3 170 670 11451971 +250.23 30.486 0.1513 1904 Perrine Himalia
12 LXXI S/2018 J 1 15.9 2 0.0015 11453004 +250.40 30.606 0.0944 2018 Sheppard et al. Himalia
13 LXV S/2017 J 4 16.2 2 0.0015 11494801 +251.77 28.155 0.1800 2017 Sheppard et al. Himalia
14 X Lysithea /lˈsɪθiə/ Lysithea2.jpg 11.3 36 6.3 11740560 +259.89 27.006 0.1322 1938 Nicholson Himalia
15 VII Elara /ˈɛlərə/
Elara2-LB1-mag17.jpg
9.9 86 87 11778034 +259.64 29.691 0.1948 1905 Perrine Himalia
16 LIII Dia /ˈdə/ 16.3 4 0.0090 12570424 +287.93 27.584 0.2058 2001 Sheppard et al. Himalia
17 XLVI Carpo /ˈkɑːrp/ 16.2 3 0.0045 17144873 +458.62 56.001 0.2735 2003 Sheppard et al. Carpo
18 (lost) S/2003 J 12 17.0 1 0.00015 17739539
(28717431±1136944)[51]
−482.69
(-944.29)[51]
142.680
(152.5±1.3)[51]
0.4449
(0.115±0.011)[51]
2003 Sheppard et al. Ananke (unconfirmed)
19 LXII Valetudo /vælɪˈtjd/ 16.9 1 18928095 +532.00 34.014 0.2219 2016 Sheppard et al. Valetudo
20 XXXIV Euporie /jˈpɒrii/ 16.4 2 0.0015 19088434 −538.78 144.694 0.0960 2002 Sheppard et al. Ananke
21 LX S/2003 J 3 16.9 2 0.0015 19621780 −561.52 146.363 0.2507 2003 Sheppard et al. Ananke
22 LV S/2003 J 18 16.5 2 0.0015 20219648 −587.38 146.376 0.1048 2003 Gladman et al. Ananke
23 LII S/2010 J 2 17.5 1 20307150 −588.36 150.4 0.307 2010 Veillet Ananke
24 XLII Thelxinoe /θɛlkˈsɪni/ 16.4 2 0.0015 20453753 −597.61 151.292 0.2684 2003 Sheppard et al. Ananke
25 XXXIII Euanthe /juˈænθi/ 16.5 3 0.0045 20464854 −598.09 143.409 0.2000 2002 Sheppard et al. Ananke
26 XLV Helike /ˈhɛlɪki/ 16.1 4 0.0090 20540266 −601.40 154.586 0.1374 2003 Sheppard et al. Ananke
27 XXXV Orthosie /ɔːrˈθɒsii/ 16.7 2 0.0015 20567971 −602.62 142.366 0.2433 2002 Sheppard et al. Ananke
28 LXVIII S/2017 J 7 16.6 2 0.0015 20571458 −602.77 143.438 0.2147 2017 Sheppard et al. Ananke
29 LIV S/2016 J 1 17.0 3 0.0015 20595483 −603.83 139.839 0.1377 2016 Sheppard et al. Ananke
30 LXIV S/2017 J 3 16.5 2 0.0015 20639315 −605.76 147.915 0.1477 2017 Sheppard et al. Ananke
31 XXIV Iocaste /ˈkæsti/ 15.5 5 0.019 20722566 −609.43 147.248 0.2874 2001 Sheppard et al. Ananke
32 (lost) S/2003 J 16 16.4 2 0.0015 20743779 −610.36 150.769 0.3184 2003 Gladman et al. Ananke
33 XXVII Praxidike /prækˈsɪdɪki/ 14.9 7 0.043 20823948 −613.90 144.205 0.1840 2001 Sheppard et al. Ananke
34 XXII Harpalyke /hɑːrˈpælɪki/ 15.9 4 0.012 21063814 −624.54 147.223 0.2440 2001 Sheppard et al. Ananke
35 XL Mneme /ˈnmi/ 16.4 2 0.0015 21129786 −627.48 149.732 0.3169 2003 Gladman et al. Ananke
36 XXX Hermippe /hərˈmɪpi/ Ερμίππη.gif 15.6 4 0.0090 21182086 −629.81 151.242 0.2290 2002 Sheppard et al. Ananke
37 XXIX Thyone /θˈni/ 15.9 4 0.0090 21405570 −639.80 147.276 0.2525 2002 Sheppard et al. Ananke
38 LXX S/2017 J 9 16.1 2 0.0015 21429955 −640.90 152.661 0.2288 2017 Sheppard et al. Ananke
39 XII Ananke /əˈnæŋki/ Ananké.jpg 12.0 28 3.0 21454952 −640.38 151.564 0.3445 1951 Nicholson Ananke
40 L Herse /ˈhɜːrsi/ 16.6 2 0.0015 22134306 −672.75 162.490 0.2379 2003 Gladman et al. Carme
41 XXXI Aitne /ˈɛtni/ 16.0 3 0.0045 22285161 −679.64 165.562 0.3927 2002 Sheppard et al. Carme
42 LXVII S/2017 J 6 16.4 2 0.0015 22394682 −684.66 155.185 0.5569 2017 Sheppard et al. Pasiphae (fringe member)
43 LXXII S/2011 J 1 16.7 1 22401817 −694.98 163.341 0.2328 2011 Sheppard et al. Carme
44 XXXVII Kale /ˈkli/ 16.4 2 0.0015 22409207 −685.32 165.378 0.2011 2002 Sheppard et al. Carme
45 XX Taygete /tˈɪɪti/ 15.6 5 0.016 22438648 −686.67 164.890 0.3678 2001 Sheppard et al. Carme
46 LXI S/2003 J 19 16.8 2 0.0015 22696750 −698.55 166.657 0.2572 2003 Gladman et al. Carme
47 XXI Chaldene /kælˈdni/ 16.0 4 0.0075 22713444 −699.33 167.070 0.2916 2001 Sheppard et al. Carme
48 LVIII S/2003 J 15 16.7 2 0.0015 22720999 −699.68 141.812 0.0932 2003 Sheppard et al. Pasiphae
49 (lost) S/2003 J 10 16.8 2 0.0015 22730813
(22462575±670198)[52]
−700.13
(-687.83)[52]
163.813
(162.38±0.90[52]
0.3438
(0.095±0.014)[52]
2003 Sheppard et al. Carme
50 (lost) S/2003 J 23 S2003j23ccircle.gif 16.8 2 0.0015 22739654 −700.54 148.849 0.3930 2004 Sheppard et al. Pasiphae
51 XXV Erinome /ɪˈrɪnmi/ 16.1 3 0.0045 22986266 −711.96 163.737 0.2552 2001 Sheppard et al. Carme
52 XLI Aoede /ˈdi/ 15.6 4 0.0090 23044175 −714.66 160.482 0.4311 2003 Sheppard et al. Pasiphae
53 XLIV Kallichore /kəˈlɪkri/ 16.3 2 0.0015 23111823 −717.81 164.605 0.2041 2003 Sheppard et al. Carme
54 LXVI S/2017 J 5 16.5 2 0.0015 23169389 −720.49 164.331 0.2842 2017 Sheppard et al. Carme
55 LXIX S/2017 J 8 17.0 1 0.0015 23174446 −720.73 164.782 0.3118 2017 Sheppard et al. Carme
56 XXIII Kalyke /ˈkælɪki/ 15.5 5 0.019 23180773 −721.02 165.505 0.2139 2001 Sheppard et al. Carme
57 XI Carme /ˈkɑːrmi/ Carmé.jpg 11.0 46 13 23197992 −702.28 165.047 0.2342 1938 Nicholson Carme
58 XVII Callirrhoe /kəˈlɪri/
S1999j1.jpg
14.1 9 0.087 23214986 −727.11 139.849 0.2582 2000 Spahr, Scotti Pasiphae
59 XXXII Eurydome /jʊəˈrɪdəmi/ 16.3 3 0.0045 23230858 −723.36 149.324 0.3769 2002 Sheppard et al. Pasiphae
60 LXIII S/2017 J 2 16.9 2 0.0015 23240957 −723.83 166.398 0.2360 2017 Sheppard et al. Carme
61 XXXVIII Pasithee /pəˈsɪθii/ 16.8 2 0.0015 23307318 −726.93 165.759 0.3288 2002 Sheppard et al. Carme
62 LI S/2010 J 1 16.5 2 23314335 −724.34 163.2 0.320 2010 Jacobson et al. Carme
63 XLIX Kore /ˈkɔːri/ 16.6 2 0.0015 23345093 −723.72 137.371 0.1951 2003 Sheppard et al. Pasiphae
64 XLVIII Cyllene /sɪˈlni/ 16.3 2 0.0015 23396269 −731.10 140.148 0.4115 2003 Sheppard et al. Pasiphae
65 LVI S/2011 J 2 16.9 1 23400981 −731.32 148.77 0.3321 2011 Sheppard et al. Pasiphae
66 XLVII Eukelade /jˈkɛlədi/ 16.0 4 0.0090 23483694 −735.20 163.996 0.2828 2003 Sheppard et al. Carme
67 LIX S/2017 J 1 16.8 2 0.0015 23483978 −734.15 149.197 0.3969 2017 Sheppard et al. Pasiphae
68 (lost) S/2003 J 4 16.7 2 0.0015 23570790
(22766748±1780215)[53]
−739.29
(-701.85)[53]
147.175
(143.2±1.3)[53]
0.3003
(0.1111±0.0077)[53]
2003 Sheppard et al. Pasiphae
69 VIII Pasiphae /pəˈsɪfi/ Pasiphaé.jpg 10.4 60 30 23609042 −739.80 141.803 0.3743 1908 Melotte Pasiphae
70 XXXIX Hegemone /hɪˈɛməni/ 16.0 3 0.0045 23702511 −745.50 152.506 0.4077 2003 Sheppard et al. Pasiphae
71 XLIII Arche /ˈɑːrki/ Bigs2002j1barrow.png 16.3 3 0.0045 23717051 −746.19 164.587 0.1492 2002 Sheppard et al. Carme
72 XXVI Isonoe /ˈsɒni/ 16.0 4 0.0075 23800647 −750.13 165.127 0.1775 2001 Sheppard et al. Carme
73 (lost) S/2003 J 9 17.0 1 0.00015 23857808 −752.84 164.980 0.2761 2003 Sheppard et al. Carme
74 LVII S/2003 J 5 15.9 4 0.0090 23973926 −758.34 165.549 0.3070 2003 Sheppard et al. Carme
75 IX Sinope /sɪˈnpi/ Sinopé.jpg 11.4 38 7.5 24057865 −739.33 153.778 0.2750 1914 Nicholson Pasiphae
76 XXXVI Sponde /ˈspɒndi/ 16.7 2 0.0015 24252627 −771.60 154.372 0.4431 2002 Sheppard et al. Pasiphae
77 XXVIII Autonoe /ɔːˈtɒni/ 15.6 4 0.0090 24264445 −772.17 151.058 0.3690 2002 Sheppard et al. Pasiphae
78 XIX Megaclite /ˌmɛɡəˈklti/ 15.0 5 0.021 24687239 −792.44 150.398 0.3077 2001 Sheppard et al. Pasiphae
79 (lost) S/2003 J 2 16.6 2 0.0015 28570410
(27734694±10756087)[54]
-981.55
(-943.69)[54]
153.521
(151.3±2.5)[54]
0.4074
(0.1197±0.0024)[54]
2003 Sheppard et al. Pasiphae (unconfirmed)

Exploration[edit]

The first spacecrafts to visit Jupiter were Pioneer 10 in 1973, and Pioneer 11 a year later, taking low-resolution images of the four Galilean moons.[55] 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.

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.[56]

See also[edit]

Notes[edit]

  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 diameter 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 have been measured well enough.
  6. ^ Periods with negative values are retrograde.
  7. ^ "?" refers to group assignments that are not considered sure yet.

References[edit]

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  55. ^ File:Pioneer-10 jupiter moons.jpg
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External links[edit]