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Jupiter's Natural SatellitesJupiter has many natural satellites. Discovery of the moons The first moons of Jupiter to be discovered were the large Galilean moons, discovered by Galileo in 1610. Over the next four centuries, nine smaller moons were discovered by ground-based astronomers. The Voyager 1 mission discovered three inner moons in 1979, bringing the total then known to 16 (17 if you count Themisto, which had been found but then lost in 1975). The total rested there until 1999, since when sensitive ground-based detectors have found a further 47 (or 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 programme discovered an asteroid, 1999 UX18. But it was soon realised that this was in fact a new moon of Jupiter, 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. Fernndez, 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 Besanon) 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, on December 9-11, 2001, eleven other moons were discovered, bringing the total to 39. The year 2002 bore less fruit, netting only one moon, Arche. However, four months later, between February 5 and 9, 2003, 23 more moons were found. References: Table of known moons Note that the outer satellites do not follow the simple period / axis relationship suggested by Kepler's third law because of the gravitational influence of the sun distorting the orbits. The table below is sorted in order of increasing period, which is not the same as the order of increasing mean orbital radius. colspan="2" style="background:#efefef;" | Name
(Pronunciation key) | style="background:#efefef;" | Diameter (km) | style="background:#efefef;" | Mass (kg) | style="background:#efefef;" | Orbital radius (km) | style="background:#efefef;" | Orbital period (d) | style="background:#efefef;" | Inclination () | style="background:#efefef;" | Eccentricity | style="background:#efefef;" | Group | | Metis | mee'-tis | align="center"| 43 | align="right"| 1.2E+16 | align="right"| 128 000 | align="right"| 0.295 | align="right"| 0.019 | align="right"| 0.0012 | rowspan="4" | Amalthea | | Adrastea | ad'-rus-tee'-a | align="center"| 262016 | align="right"| 7.5E+14 | align="right"| 129 000 | align="right"| 0.298 | align="right"| 0.054 | align="right"| 0.0018 | | Amalthea | am'-ul-thee'-a | align="center"| 262146134 | align="right"| 0.2E+18 | align="right"| 181 400 | align="right"| 0.498 | align="right"| 0.388 | align="right"| 0.0031 | | Thebe | thee'-bee | align="center"| 11090 | align="right"| 0.1E+18 | align="right"| 221 900 | align="right"| 0.675 | align="right"| 1.070 | align="right"| 0.0177 | | Io | eye'-oh | align="center"| 3643 | align="right"| 0.9E+22 | align="right"| 421 800 | align="right"| 1.769 | align="right"| 0.036 | align="right"| 0.0041 | rowspan="4" | Galileans | | Europa | ew-roh'-pa | align="center"| 3122 | align="right"| 0.5E+22 | align="right"| 671 100 | align="right"| 3.551 | align="right"| 0.469 | align="right"| 0.0094 | | Ganymede | gan'-i-meed | align="center"| 5262 | align="right"| 1.5E+22 | align="right"| 1 070 400 | align="right"| 7.155 | align="right"| 0.170 | align="right"| 0.0011 | | Callisto | ka-lis'-toh | align="center"| 4821 | align="right"| 1.1E+22 | align="right"| 1 882 700 | align="right"| 6.690 | align="right"| 0.187 | align="right"| 0.0074 | | Themisto | the-mis'-toh | align="center"| 8 | align="right"| 0.7E+14 | align="right"| 7 284 000 | align="right"| 130.020 | align="right"| 43.259 | align="right"| 0.2426 | rowspan="1" | Themisto | | Leda | lee'-da | align="center"| 20 | align="right"| 0.1E+16 | align="right"| 11 165 000 | align="right"| 240.920 | align="right"| 27.457 | align="right"| 0.1636 | rowspan="5" | Himalia | | Himalia | hye-mal'-ee-a | align="center"| 170 | align="right"| 0.7E+18 | align="right"| 11 461 000 | align="right"| 250.560 | align="right"| 27.496 | align="right"| 0.1623 | | Lysithea | lye-sith'-ee-a | align="center"| 36 | align="right"| 0.6E+16 | align="right"| 11 717 000 | align="right"| 259.200 | align="right"| 28.302 | align="right"| 0.1124 | | Elara | ee-lair'-a | align="center"| 86 | align="right"| 8.7E+16 | align="right"| 11 741 000 | align="right"| 259.640 | align="right"| 26.627 | align="right"| 0.2174 | | colspan="2" | S/2000 J 11 | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 12 555 000 | align="right"| 286.950 | align="right"| 28.273 | align="right"| 0.2484 | | Carpo | kar'-poh | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 16 989 000 | align="right"| 456.100 | align="right"| 51.395 | align="right"| 0.4297 | rowspan="1" | ? | | colspan="2" | S/2003 J 12 | align="center"| 1 | align="right"| 0.1E+12 | align="right"| 17 582 000 | align="right"| 489.500 | align="right"| 151.140 | align="right"| 0.5095 | rowspan="1" | ? | | Euporie | ew-por'-ee-a | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 19 304 000 | align="right"| 550.740 | align="right"| 145.767 | align="right"| 0.1432 | rowspan="3" | Ananke? | | colspan="2" | S/2003 J 3 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 20 221 000 | align="right"| 583.880 | align="right"| 147.550 | align="right"| 0.1970 | | colspan="2" | S/2003 J 18 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 20 514 000 | align="right"| 596.590 | align="right"| 146.104 | align="right"| 0.0221 | | colspan="2" | S/2003 J 16 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 20 957 000 | align="right"| 616.360 | align="right"| 148.537 | align="right"| 0.2246 | rowspan="3" | Ananke | | Mneme | nee'-mee | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 21 069 000 | align="right"| 620.040 | align="right"| 148.635 | align="right"| 0.2273 | | Euanthe | ew-an'-thee | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 20 797 000 | align="right"| 620.490 | align="right"| 148.910 | align="right"| 0.2321 | | Orthosie | or-thoh'-see-a | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 20 720 000 | align="right"| 622.560 | align="right"| 145.921 | align="right"| 0.2808 | rowspan="1" | Ananke? | | Harpalyke | har-pal'-i-kee | align="center"| 4 | align="right"| 0.1E+14 | align="right"| 20 858 000 | align="right"| 623.310 | align="right"| 148.644 | align="right"| 0.2268 | rowspan="3" | Ananke | | Praxidike | prak-sid'-i-kee | align="center"| 7 | align="right"| 0.4E+14 | align="right"| 20 907 000 | align="right"| 625.380 | align="right"| 148.967 | align="right"| 0.2308 | | Thyone | thye-oh'-nee | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 20 939 000 | align="right"| 627.210 | align="right"| 148.509 | align="right"| 0.2286 | | Thelxinoe | thel-zin'-oh-ee? | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 21 162 000 | align="right"| 628.090 | align="right"| 151.417 | align="right"| 0.2206 | rowspan="1" | Ananke? | | Ananke | a-nang'-kee | align="center"| 28 | align="right"| 0.3E+16 | align="right"| 21 276 000 | align="right"| 629.770 | align="right"| 148.889 | align="right"| 0.2435 | rowspan="2" | Ananke | | Iocaste | eye'-o-kas'-tee | align="center"| 5 | align="right"| 0.2E+14 | align="right"| 21 061 000 | align="right"| 631.600 | align="right"| 149.429 | align="right"| 0.2160 | | Hermippe | hur-mip'-ee | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 21 131 000 | align="right"| 633.900 | align="right"| 150.725 | align="right"| 0.2096 | rowspan="3" | Ananke? | | Helike | hel'-i-kee | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 21 263 000 | align="right"| 634.770 | align="right"| 154.773 | align="right"| 0.1558 | | colspan="2" | S/2003 J 15 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 22 627 000 | align="right"| 689.770 | align="right"| 146.501 | align="right"| 0.1910 | | colspan="2" | S/2003 J 17 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 22 992 000 | align="right"| 714.470 | align="right"| 164.917 | align="right"| 0.2378 | rowspan="1" | Carme | | colspan="2" | S/2003 J 10 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 041 000 | align="right"| 716.250 | align="right"| 165.086 | align="right"| 0.4295 | rowspan="1" | Carme? | | Eurydome | ew-rid'-o-mee? | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 22 865 000 | align="right"| 717.330 | align="right"| 150.274 | align="right"| 0.2759 | rowspan="1" | Pasipha? | | Pasithee | pa-sith'-ee-a | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 004 000 | align="right"| 719.440 | align="right"| 165.138 | align="right"| 0.2675 | rowspan="8" | Carme | | Chaldene | ? | align="center"| 4 | align="right"| 7.5E+12 | align="right"| 23 100 000 | align="right"| 723.700 | align="right"| 165.191 | align="right"| 0.2519 | | Arche | ar'-kee | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 22 931 000 | align="right"| 723.900 | align="right"| 165.001 | align="right"| 0.2588 | | Isonoe | eye-son'-oh-ee? | align="center"| 4 | align="right"| 7.5E+12 | align="right"| 23 155 000 | align="right"| 726.250 | align="right"| 165.268 | align="right"| 0.2471 | | Erinome | ? | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 23 196 000 | align="right"| 728.510 | align="right"| 164.934 | align="right"| 0.2665 | | Kale | kay'-lee | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 217 000 | align="right"| 729.470 | align="right"| 164.996 | align="right"| 0.2599 | | Aitne | et'-nee | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 23 229 000 | align="right"| 730.180 | align="right"| 165.091 | align="right"| 0.2643 | | Taygete | tay-ij'-i-tee | align="center"| 5 | align="right"| 0.2E+14 | align="right"| 23 280 000 | align="right"| 732.410 | align="right"| 165.272 | align="right"| 0.2525 | | colspan="2" | S/2003 J 23 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 563 000 | align="right"| 732.440 | align="right"| 146.314 | align="right"| 0.2714 | rowspan="1" | Pasipha | | colspan="2" | S/2003 J 9 | align="center"| 1 | align="right"| 0.1E+12 | align="right"| 23 384 000 | align="right"| 733.290 | align="right"| 165.079 | align="right"| 0.2632 | rowspan="3" | Carme | | Carme | kar'-mee | align="center"| 46 | align="right"| 1.3E+16 | align="right"| 23 404 000 | align="right"| 734.170 | align="right"| 164.907 | align="right"| 0.2533 | | colspan="2" | S/2003 J 5 | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 23 495 000 | align="right"| 738.730 | align="right"| 165.247 | align="right"| 0.2478 | | Hegemone | hi-jem'-a-nee? | align="center"| 3 | align="right"| 4.5E+12 | align="right"| 23 947 000 | align="right"| 739.600 | align="right"| 155.214 | align="right"| 0.3276 | rowspan="1" | Pasipha | | colspan="2" | S/2003 J 19 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 533 000 | align="right"| 740.420 | align="right"| 165.153 | align="right"| 0.2556 | rowspan="2" | Carme | | Kalyke | kal'-i-kee | align="center"| 5 | align="right"| 0.2E+14 | align="right"| 23 566 000 | align="right"| 742.030 | align="right"| 165.159 | align="right"| 0.2465 | | Pasipha | pa-sif'-a-ee | align="center"| 60 | align="right"| 3.0E+16 | align="right"| 23 624 000 | align="right"| 743.630 | align="right"| 151.431 | align="right"| 0.4090 | rowspan="1" | Pasipha | | Eukelade | ew-kel'-a-dee? | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 23 661 000 | align="right"| 746.390 | align="right"| 165.482 | align="right"| 0.2721 | rowspan="1" | Carme | | Sponde | spon'-dee | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 487 000 | align="right"| 748.340 | align="right"| 150.998 | align="right"| 0.3121 | rowspan="8" | Pasipha | | Cyllene | si-lee'-nee | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 951 000 | align="right"| 751.940 | align="right"| 150.123 | align="right"| 0.4116 | | Megaclite | meg'-a-klye'-tee? | align="center"| 5 | align="right"| 0.2E+14 | align="right"| 23 493 000 | align="right"| 752.880 | align="right"| 152.769 | align="right"| 0.4197 | | colspan="2" | S/2003 J 4 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 23 930 000 | align="right"| 755.240 | align="right"| 149.581 | align="right"| 0.3618 | | Callirrhoe | ka-leer'-oh-ee | align="center"| 9 | align="right"| 0.9E+14 | align="right"| 24 103 000 | align="right"| 758.770 | align="right"| 147.158 | align="right"| 0.2828 | | Sinope | si-noh'-pee | align="center"| 38 | align="right"| 0.7E+16 | align="right"| 23 939 000 | align="right"| 758.900 | align="right"| 158.109 | align="right"| 0.2495 | | Autonoe | aw-ton'-oh-ee | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 24 046 000 | align="right"| 760.950 | align="right"| 152.416 | align="right"| 0.3168 | | Aoede | ay-ee'-dee? | align="center"| 4 | align="right"| 9.0E+12 | align="right"| 23 981 000 | align="right"| 761.500 | align="right"| 158.257 | align="right"| 0.4322 | | Kallichore | ? | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 24 043 000 | align="right"| 764.730 | align="right"| 165.501 | align="right"| 0.2640 | rowspan="1" | Carme? | | colspan="2" | S/2003 J 14 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 24 011 000 | align="right"| 779.180 | align="right"| 144.529 | align="right"| 0.3351 | rowspan="1" | Pasipha | | colspan="2" | S/2003 J 2 | align="center"| 2 | align="right"| 1.5E+12 | align="right"| 29 541 000 | align="right"| 979.990 | align="right"| 160.638 | align="right"| 0.2255 | rowspan="1" | ? | The orbits of the unnamed moons are still susceptible of improvement. Grouping the moons The interior groups seem natural: Amalthea's, the Galilean moons. Themisto is isolated in space. The 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. Carpo and S/2003 J 12 are two other isolated cases, and so is S/2003 J 2, the most exterior moon. What is left of the outer retrograde irregular satellites of Jupiter can be grouped in 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. In the two plots below, Carme's group is in orange and Ananke's in yellow. Carme's group is obvious, centered on a = 23 404 Mm; i = 165.20.3 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 = 149.00.5 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. Pasipha'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 = 151.46.9 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. Naming notes Some asteroids share the same names as moons of Jupiter: 9 Metis, 38 Leda, 52 Europa, 85 Io, 113 Amalthea, 239 Adrastea, 1036 Ganymed. Note that the satellites discovered between 1904 and 1951 (Himalia, Elara, Pasipha, Sinope, Lysithea, Carme and Ananke) were not officially named until 1975, well after their discoverers had passed away. They were simply known by their Roman numeral designations (Jupiter VI through Jupiter XII). See Naming of natural satellites. See also External links
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