Moons of Jupiter

For other uses, see Moons of Jupiter (disambiguation).

There are 84 known moons of Jupiter as of 2023^[update], not counting a number of moonlets likely shed from the inner moons. 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 80 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 are just massive enough that they would be considered major 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

 

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 evolution

 

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.^[1][2] They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history.^[1][3]

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.^[1] 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.^[1] By the time the present (possibly fifth) generation formed, the disk had thinned so that it no longer greatly interfered with the moons' orbits.^[3] 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: they are in a 1:2:4 resonance. Ganymede's larger mass means that it would have migrated inward at a faster rate than Europa or Io.^[1] Tidal dissipation in the Jovian system is still ongoing and Callisto will likely be captured into the resonance in about 1.5 billion years, creating a 1:2:4:8 chain.^[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.^[5]

Discovery

 

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

See also: Timeline of discovery of Solar System planets and their moons

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".^[6] However, the first certain observations of Jupiter's satellites were those of Galileo Galilei in 1609.^[7] By January 1610, he had sighted the four massive Galilean moons with his 20× magnification telescope, and he published his results in March 1610.^[8]

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.^[9] No additional satellites were discovered until E. E. Barnard observed Amalthea in 1892.^[10]

With the aid of telescopic photography, further discoveries followed quickly over the course of the 20th century. Himalia was discovered in 1904,^[11] Elara in 1905,^[12] Pasiphae in 1908,^[13] Sinope in 1914,^[14] Lysithea and Carme in 1938,^[15] Ananke in 1951,^[16] and Leda in 1974.^[17]

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,^[18] 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.^[19]

 

The number of moons known for each of the four outer planets up to October 2019. Jupiter currently has 84 known satellites.

No additional moons were discovered until two decades later, with the fortuitous discovery of Callirrhoe by the Spacewatch survey in October 1999.^[20] During the 1990s, digital charge-coupled device (CCD) cameras began emerging in large-aperture telescopes on Earth, allowing for wide-field surveys of the sky at unprecedented sensitivities, thus ushering in a wave of new moon discoveries.^[21] Scott Sheppard, then a graduate student of David Jewitt, demonstrated this extended capability of CCD cameras in a survey conducted with the Mauna Kea Observatory's 2.2-meter UH88 telescope in November 2000, discovering eleven new irregular moons of Jupiter including the previously-lost Themisto.^[22]

From 2001 onward, Sheppard and Jewitt alongside other collaborators continued surveying for irregular moons of Jupiter with the 3.6-m Canada-France-Hawaii Telescope (CFHT), discovering an additional eleven in December 2001, one in October 2002, and nineteen in February 2003.^[22][23] At the same time, another independent team led by Brett Gladman also used the CFHT in 2003 to search for irregular moons of Jupiter, discovering four and co-discovering two with Sheppard.^[23][24][25] From the start to end of these CCD-based surveys in 2000–2004, Jupiter's known moon count had grown from 17 to 63.^[20][24] All of these moons discovered after 2000 are tiny and faint, with diameters less than 10 km (6.2 mi) and apparent magnitudes between 22–23.^[22] As a result, many could not be reliably tracked and ended up becoming lost for several years.^[26]

By 2015, a total of 15 additional moons were discovered.^[27] Two more were discovered in 2017 by the team led by Scott S. Sheppard at the Carnegie Institution for Science, bringing the total to 69.^[28] 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.^[29] 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] From November 2021 to January 2023, several more moons of Jupiter were reported in archival data from 2003–2018, plus one from 2021.

Naming

Main article: Naming of moons

 

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.^[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][33] 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.^[34][35]

The other moons were simply labeled by their Roman numeral (e.g. Jupiter IX) in the majority of astronomical literature until the 1970s.^[36] 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,^[37] and provided for a formal naming process for future satellites still to be discovered.^[37] 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.^[34] All of Jupiter's satellites from XXXIV (Euporie) onward are named after descendants of Jupiter or Zeus,^[34] 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.^[38] 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).^[39] 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.

Groups

 

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

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.^[40] 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.^[41][42]
• 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, 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.^[43] Europa, Ganymede, and Callisto are suspected of having subsurface water oceans,^[44][45] and Io may have a subsurface magma ocean.^[46]

Irregular satellites

 

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.

Main article: Irregular satellite

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:^[47][48][49]

• Prograde satellites:
  • Themisto is the innermost irregular moon and is not part of a known family.^[47][48]
  • 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.^[48]
  • Carpo is another prograde moon and is not part of a known family. It has the highest inclination of all of the prograde moons.^[47]
  • 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.^[29]
• 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.^[50]
  • 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.^[50]
  • 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.^[50] The colors also vary significantly, from red to grey, which might be the result of multiple collisions. Sinope, sometimes included in the Pasiphae group,^[50] is red and, given the difference in inclination, it could have been captured independently;^[48] Pasiphae and Sinope are also trapped in secular resonances with Jupiter.^[51]

In September 2020, researchers from the University of British Columbia identified 45 candidate irregular moons from an analysis of archival images taken in 2010 by the CFHT.^[52] 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.^[53] 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.^[52]

List

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,^[54] therefore the listed orbital elements of all irregular moons are averaged over a 400-year numerical integration. Their orbital elements are all based on the epoch of 1 January 2000.^[55] 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.^[54]

Key
Inner moons	♠ Galilean moons	† Ungrouped moons	♣ Himalia group	♦ Ananke group	♥ Carme group	‡ Pasiphae group

Label ^[note 3]	Name	Pronunciation	Image	Abs. magn.	Diameter (km)^[47]^[note 4]	Mass (×10^16 kg)^[56]^[note 5]	Semi-major axis (km)^[55]	Orbital period (d) ^[55]^[note 6]	Inclination (°)^[55]	Eccentricity ^[47]	Discovery year^[23]	Year announced	Discoverer^[23]	Group ^[note 7]
XVI	Metis	/ˈmiːtəs/		10.5	43 (60 × 40 × 34)	≈ 3.6	128000	+0.2948 (+7h 04m 29s)	0.060	0.0002	1979	1980	Synnott (Voyager 1)	Inner
XV	Adrastea	/ædrəˈstiːə/		12.0	16.4 (20 × 16 × 14)	≈ 0.20	129000	+0.2983 (+7h 09m 30s)	0.030	0.0015	1979	1979	Jewitt (Voyager 2)	Inner
V	Amalthea	/æməlˈθiːə/^[57]		7.1	167 (250 × 146 × 128)	208	181400	+0.4999 (+11h 59m 53s)	0.374	0.0032	1892	1892	Barnard	Inner
XIV	Thebe	/ˈθiːbiː/		9.0	98.6 (116 × 98 × 84)	≈ 43	221900	+0.6761 (+16h 13m 35s)	1.076	0.0175	1979	1980	Synnott (Voyager 1)	Inner
I	Io♠	/ˈaɪoʊ/		−1.7	3643.2 (3660 × 3637 × 3631)	8931900	421800	+1.7627	0.050^[58]	0.0041	1610	1610	Galileo	Galilean
II	Europa♠	/jʊəˈroʊpə/^[59]		−1.4	3121.6	4799800	671100	+3.5255	0.470^[58]	0.0090	1610	1610	Galileo	Galilean
III	Ganymede♠	/ˈɡænəmiːd/^[60]^[61]		−2.1	5268.2	14819000	1070400	+7.1556	0.200^[58]	0.0013	1610	1610	Galileo	Galilean
IV	Callisto♠	/kəˈlɪstoʊ/		−1.2	4820.6	10759000	1882700	+16.690	0.192^[58]	0.0074	1610	1610	Galileo	Galilean
XVIII	Themisto†	/θəˈmɪstoʊ/		12.9	9	≈ 0.038	7398500	+130.03	43.8	0.340	1975/2000	1975	Kowal & Roemer/ Sheppard et al.	Themisto
XIII	Leda♣	/ˈliːdə/		12.7	21.5	≈ 0.52	11146400	+240.93	28.6	0.162	1974	1974	Kowal	Himalia
LXXI	Ersa♣	/ˈɜːrsə/		15.9	3	≈ 0.0014	11401000	+249.23	29.1	0.116	2018	2018	Sheppard	Himalia
VI	Himalia♣	/hɪˈmeɪliə/		7.9	139.6 (150 × 120)	420	11440600	+250.56	28.1	0.160	1904	1905	Perrine	Himalia
	S/2018 J 2♣			16.5	3	≈ 0.0014	11467500	+250.88	29.4	0.118	2018	2022	Sheppard	Himalia
LXV	Pandia♣	/pænˈdaɪə/		16.2	3	≈ 0.0014	11481000	+251.91	29.0	0.179	2017	2018	Sheppard	Himalia
X	Lysithea♣	/laɪˈsɪθiə/		11.2	42.2	≈ 3.9	11700800	+259.20	27.2	0.117	1938	1938	Nicholson	Himalia
VII	Elara♣	/ˈɛlərə/		9.6	79.9	≈ 27	11712300	+259.64	27.9	0.211	1905	1905	Perrine	Himalia
	S/2011 J 3♣			16.3	3	≈ 0.0014	11797200	+261.77	28.7	0.176	2011	2022	Sheppard	Himalia
LIII	Dia♣	/ˈdaɪə/		16.3	4	≈ 0.0034	12260300	+278.21	29.0	0.232	2000	2001	Sheppard et al.	Himalia
XLVI	Carpo†	/ˈkɑːrpoʊ/		16.1	3	≈ 0.0014	17042300	+456.29	53.2	0.416	2003	2003	Sheppard	Carpo
LXII	Valetudo†	/væləˈtjuːdoʊ/		17.0	1	≈ 0.000052	18694200	+527.61	34.5	0.217	2016	2018	Sheppard	Valetudo
XXXIV	Euporie♦	/ˈjuːpəriː/		16.3	2	≈ 0.00042	19265800	−550.69	145.7	0.148	2001	2002	Sheppard et al.	Ananke
LV	S/2003 J 18♦			16.5	2	≈ 0.00042	20336300	−598.12	145.3	0.090	2003	2003	Gladman	Ananke
	S/2021 J 1♦			17.3	1	≈ 0.000052	20667200	−606.99	149.8	0.246	2021	2023	Sheppard	Ananke
LX	Eupheme♦	/juːˈfiːmiː/		16.6	2	≈ 0.00042	20768600	−617.73	148.0	0.241	2003	2003	Sheppard	Ananke
LII	S/2010 J 2♦			17.3	1	≈ 0.000052	20793000	−618.84	148.1	0.248	2010	2011	Veillet	Ananke
LIV	S/2016 J 1♦			16.8	1	≈ 0.000052	20802600	−618.49	144.7	0.232	2016	2017	Sheppard	Ananke
XL	Mneme♦	/ˈniːmiː/		16.3	2	≈ 0.00042	20821000	−620.07	148.0	0.247	2003	2003	Sheppard & Gladman	Ananke
XXXIII	Euanthe♦	/juːˈænθiː/		16.4	3	≈ 0.0014	20827000	−620.44	148.0	0.239	2001	2002	Sheppard et al.	Ananke
	S/2003 J 16♦			16.3	2	≈ 0.00042	20882600	−622.88	148.0	0.243	2003	2003	Gladman	Ananke
XXII	Harpalyke♦	/hɑːrˈpæləkiː/		15.9	4	≈ 0.0034	20892100	−623.32	147.7	0.232	2000	2001	Sheppard et al.	Ananke
XXXV	Orthosie♦	/ɔːrˈθoʊziː/		16.7	2	≈ 0.00042	20901000	−622.59	144.3	0.299	2001	2002	Sheppard et al.	Ananke
XLV	Helike♦	/ˈhɛləkiː/		16.0	4	≈ 0.0034	20915700	−626.33	154.4	0.153	2003	2003	Sheppard	Ananke
XXVII	Praxidike♦	/prækˈsɪdəkiː/		14.9	7	≈ 0.018	20935400	−625.39	148.3	0.246	2000	2001	Sheppard et al.	Ananke
LXIV	S/2017 J 3♦			16.5	2	≈ 0.00042	20941000	−625.60	147.9	0.231	2017	2018	Sheppard	Ananke
	S/2003 J 12♦			17.0	1	≈ 0.000052	20963100	−627.24	150.0	0.235	2003	2003	Sheppard	Ananke
LXVIII	S/2017 J 7♦			16.6	2	≈ 0.00042	20964800	−626.56	147.3	0.233	2017	2018	Sheppard	Ananke
XLII	Thelxinoe♦	/θɛlkˈsɪnoʊiː/		16.3	2	≈ 0.00042	20976000	−628.03	150.6	0.228	2003	2004	Sheppard & Gladman	Ananke
XXIX	Thyone♦	/θaɪˈoʊniː/		15.8	4	≈ 0.0034	20978000	−627.18	147.5	0.233	2001	2002	Sheppard et al.	Ananke
	S/2003 J 2♦			16.7	2	≈ 0.00042	20997700	−628.79	150.2	0.225	2003	2003	Sheppard	Ananke
XII	Ananke♦	/əˈnæŋkiː/		11.7	29.1	≈ 1.3	21034500	−629.79	147.6	0.237	1951	1951	Nicholson	Ananke
XXIV	Iocaste♦	/aɪəˈkæstiː/		15.4	5	≈ 0.0065	21066700	−631.59	148.8	0.227	2000	2001	Sheppard et al.	Ananke
XXX	Hermippe♦	/hərˈmɪpiː/		15.6	4	≈ 0.0034	21108500	−633.90	150.2	0.219	2001	2002	Sheppard et al.	Ananke
LXX	S/2017 J 9♦			16.1	3	≈ 0.0014	21768700	−666.11	155.5	0.200	2017	2018	Sheppard	Ananke
	S/2016 J 3♥			16.7	2	≈ 0.00042	22213500	−676.37	164.1	0.236	2016	2023	Sheppard	Carme
LVIII	Philophrosyne‡	/fɪləˈfrɒzəniː/		16.7	2	≈ 0.00042	22604600	−702.54	146.3	0.229	2003	2003	Sheppard	Pasiphae
XXXVIII	Pasithee♥	/ˈpæsəθiː/		16.8	2	≈ 0.00042	22846700	−719.47	164.6	0.270	2001	2002	Sheppard et al.	Carme
LXIX	S/2017 J 8♥			17.0	1	≈ 0.000052	22849500	−719.76	164.8	0.255	2017	2018	Sheppard	Carme
	S/2003 J 24♥			16.6	3	≈ 0.0014	22887400	−721.60	164.5	0.259	2003	2021	Sheppard et al.	Carme
XXXII	Eurydome‡	/jʊəˈrɪdəmiː/		16.2	3	≈ 0.0014	22899000	−717.31	149.1	0.294	2001	2002	Sheppard et al.	Pasiphae
LVI	S/2011 J 2‡			16.8	1	≈ 0.000052	22909200	−718.32	151.9	0.355	2011	2012	Sheppard	Pasiphae
	S/2003 J 4‡			16.7	2	≈ 0.00042	22926500	−718.10	148.2	0.328	2003	2003	Sheppard	Pasiphae
XXI	Chaldene♥	/kælˈdiːniː/		16.0	4	≈ 0.0034	22930500	−723.71	164.7	0.265	2000	2001	Sheppard et al.	Carme
LXIII	S/2017 J 2♥			16.4	2	≈ 0.00042	22953200	−724.71	164.5	0.272	2017	2018	Sheppard	Carme
XXVI	Isonoe♥	/aɪˈsɒnoʊiː/		16.0	4	≈ 0.0034	22981300	−726.27	164.8	0.249	2000	2001	Sheppard et al.	Carme
XLIV	Kallichore♥	/kəˈlɪkəriː/		16.4	2	≈ 0.00042	23021800	−728.26	164.8	0.252	2003	2003	Sheppard	Carme
XXV	Erinome♥	/ɛˈrɪnəmiː/		16.0	3	≈ 0.0014	23032900	−728.48	164.4	0.276	2000	2001	Sheppard et al.	Carme
XXXVII	Kale♥	/ˈkeɪliː/		16.4	2	≈ 0.00042	23052600	−729.64	164.6	0.262	2001	2002	Sheppard et al.	Carme
LVII	Eirene♥	/aɪˈriːniː/		15.8	4	≈ 0.0034	23055800	−729.84	164.6	0.258	2003	2003	Sheppard	Carme
XXXI	Aitne♥	/ˈeɪtniː/		16.0	3	≈ 0.0014	23064400	−730.10	164.6	0.277	2001	2002	Sheppard et al.	Carme
XLVII	Eukelade♥	/juːˈkɛlədiː/		15.9	4	≈ 0.0034	23067400	−730.30	164.6	0.277	2003	2003	Sheppard	Carme
XLIII	Arche♥	/ˈɑːrkiː/		16.2	3	≈ 0.0014	23097800	−731.88	164.6	0.261	2002	2002	Sheppard	Carme
XX	Taygete♥	/teɪˈɪdʒətiː/		15.5	5	≈ 0.0065	23108000	−732.45	164.7	0.253	2000	2001	Sheppard et al.	Carme
LXXII	S/2011 J 1♥			16.7	2	≈ 0.00042	23124500	−733.21	164.6	0.271	2011	2012	Sheppard	Carme
XI	Carme♥	/ˈkɑːrmiː/		10.6	46.7	≈ 5.3	23144400	−734.19	164.6	0.256	1938	1938	Nicholson	Carme
L	Herse♥	/ˈhɜːrsiː/		16.5	2	≈ 0.00042	23150500	−734.52	164.4	0.262	2003	2003	Gladman et al.	Carme
LXI	S/2003 J 19♥			16.6	2	≈ 0.00042	23156400	−734.78	164.7	0.265	2003	2003	Gladman	Carme
LI	S/2010 J 1♥			16.4	2	≈ 0.00042	23189800	−736.51	164.5	0.252	2010	2011	Jacobson et al.	Carme
	S/2003 J 9♥			16.9	1	≈ 0.000052	23199400	−736.86	164.8	0.263	2003	2003	Sheppard	Carme
LXVI	S/2017 J 5♥			16.5	2	≈ 0.00042	23206200	−737.28	164.8	0.257	2017	2018	Sheppard	Carme
LXVII	S/2017 J 6‡			16.4	2	≈ 0.00042	23245300	−733.99	149.7	0.336	2017	2018	Sheppard	Pasiphae
XXIII	Kalyke♥	/ˈkæləkiː/		15.4	6.9	≈ 0.017	23302600	−742.02	164.8	0.260	2000	2001	Sheppard et al.	Carme
XXXIX	Hegemone‡	/həˈdʒɛməniː/		15.9	3	≈ 0.0014	23348700	−739.81	152.6	0.358	2003	2003	Sheppard	Pasiphae
VIII	Pasiphae‡	/pəˈsɪfeɪiː/		10.1	57.8	≈ 10	23468200	−743.61	148.4	0.412	1908	1908	Melotte	Pasiphae
XXXVI	Sponde‡	/ˈspɒndiː/		16.7	2	≈ 0.00042	23543300	−748.29	149.3	0.322	2001	2002	Sheppard et al.	Pasiphae
	S/2003 J 10♥			16.9	2	≈ 0.00042	23576300	−755.43	164.4	0.264	2003	2003	Sheppard	Carme
XIX	Megaclite‡	/ˌmɛɡəˈklaɪtiː/		15.0	5	≈ 0.0065	23644600	−752.86	149.8	0.421	2000	2001	Sheppard et al.	Pasiphae
XLVIII	Cyllene‡	/səˈliːniː/		16.3	2	≈ 0.00042	23654700	−751.97	146.8	0.419	2003	2003	Sheppard	Pasiphae
IX	Sinope‡	/səˈnoʊpiː/		11.1	35	≈ 2.2	23683900	−758.85	157.3	0.264	1914	1914	Nicholson	Pasiphae
LIX	S/2017 J 1‡			16.6	2	≈ 0.00042	23744800	−756.41	145.8	0.328	2017	2017	Sheppard	Pasiphae
XLI	Aoede‡	/eɪˈiːdiː/		15.6	4	≈ 0.0034	23778200	−761.46	155.7	0.436	2003	2003	Sheppard	Pasiphae
XXVIII	Autonoe‡	/ɔːˈtɒnoʊiː/		15.5	4	≈ 0.0034	23792500	−761.00	150.8	0.330	2001	2002	Sheppard et al.	Pasiphae
XVII	Callirrhoe‡	/kəˈlɪroʊiː/		13.9	9.6	≈ 0.046	23795500	−758.86	145.1	0.297	1999	2000	Scotti et al.	Pasiphae
	S/2003 J 23‡			16.6	2	≈ 0.00042	23829300	−760.00	144.7	0.313	2003	2004	Sheppard	Pasiphae
XLIX	Kore‡	/ˈkɔːriː/		16.6	2	≈ 0.00042	24205200	−776.76	141.5	0.328	2003	2003	Sheppard	Pasiphae

Exploration

Main articles: Exploration of Jupiter, Ganymede (moon) § Exploration, Europa (moon) § Exploration, Callisto (moon) § Exploration, and Io (moon) § Observational history

 

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

Nine spacecraft have visited Jupiter. The first 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.^[62] 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. Ulysses further studied Jupiter's magnetosphere in 1992 and then again in 2000.

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.

Then 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.

 

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.^[63]

See also

• Jupiter's moons in fiction
• Satellite system (astronomy)

Notes

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. Label refers to the Roman numeral attributed to each moon in order of their naming.
4. 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.
5. The only satellites with measured masses are Amalthea, Himalia, and the four Galilean moons. The masses of the inner satellites are estimated by assuming a density similar to Amalthea's (0.86 g/cm³), while the rest of the irregular satellites are estimated by assuming a spherical volume and a density of 1 g/cm³.
6. Periods with negative values are retrograde.
7. "?" refers to group assignments that are not considered sure yet.

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External links

 

Wikimedia Commons has media related to Moons of Jupiter.

• Scott S. Sheppard: Moons of Jupiter
• Scott S. Sheppard: The Jupiter Satellite and Moon Page
• by NASA's Solar System Exploration
• Archive of Jupiter System Articles in Planetary Science Research Discoveries
• Tilmann Denk: Outer Moons of Jupiter