Carme group

The Carme group is a group of retrograde irregular satellites of Jupiter that follow similar orbits to Carme and are thought to have a common origin.

This diagram illustrates the largest irregular satellites of Jupiter. The location of the Carme group is illustrated by Carme's presence in the lower middle. An object's position on the horizontal axis indicates its distance from Jupiter. The vertical axis indicates its inclination. Eccentricity is indicated by yellow bars illustrating the object's maximum and minimum distances from Jupiter. Circles illustrate an object's size in comparison to the others.

Their semi-major axes (distances from Jupiter) range between 22.7 and 23.6 Gm, their orbital inclinations between 164.4° and 164.9°, and their orbital eccentricities between 0.25 and 0.28 (with one exception).

The Carme group members are (in order by date announcement):^[1][2]

This diagram compares the orbital elements and relative sizes of the core members of the Carme group. The horizontal axis illustrates their average distance from Jupiter, the vertical axis their orbital inclination, and the circles their relative sizes.

Name	Diameter (km)[3]	Semi-Major Axis (km)	Period (days)[4][a]	Notes
Carme	46	23139200	–719.28	largest member and group prototype
Kalyke	5	23298000	–726.70	substantially redder than the others
Erinome	3	23027200	–714.05
Isonoe	4	22976300	–711.66
Taygete	5	23103400	–717.59
Chaldene	4	22926300	–709.36
Pasithee	2	22840800	–705.41
Kale	2	23047800	–715.02
Aitne	3	23059400	–715.54
Arche	3	23093200	–717.11
Eukelade	4	23062400	–715.69
Eirene	4	23051300	–715.19
S/2003 J 9	1	23195100	–721.88
S/2003 J 10	2	23384400	–730.74
Kallichore	2	23017100	–713.59
Herse	2	23146700	–719.63
S/2003 J 19	2	23153100	–719.92
S/2003 J 24	2	22882400	–707.33
S/2010 J 1	2	23185600	–721.43
S/2011 J 1	2	23120800	–718.42
S/2017 J 2	2	22949600	–710.42
S/2017 J 5	2	23202000	–722.20
S/2017 J 8	1	22819600	–704.42
S/2016 J 3	2	22719300	–699.76
S/2018 J 3	1	23400200	–731.49
S/2021 J 4	1	23019700	–713.71
S/2021 J 5	2	23414600	–732.15
S/2021 J 6	1	22870400	–706.77
S/2022 J 1	2	22744700	–700.93
S/2022 J 2	1	23073400	–716.21
S/2017 J 11	2	22991300	–712.38

The International Astronomical Union (IAU) reserves names ending in -e for all retrograde moons.

Origin

The very low dispersion of the mean orbital elements^[b] among the core members (the group is separated by less than 900,000 km in semi major axis and only 0.5° in inclination) suggests that the Carme group may once have been a single body that was broken apart by an impact. The dispersion can be explained by a very small velocity impulse (5 < δV < 50 m/s).^[5] The parent body was probably about the size of Carme, 46 km in diameter; 99% of the group's mass is still located in Carme.^[6]

Further support to the single body origin comes from the known colours: all the satellites appear light red,^[c] with colour indices B-V= 0.76 and V-R= 0.47^[7] and infrared spectra, similar to D-type asteroids.^[8] These data are consistent with a progenitor from the Hilda family or a Jupiter trojan.

This diagram shows the Ananke group on the same scale as the other diagram, illustrating its wide dispersion in comparison with the compact Carme group.

This diagram shows the compactness of the Carme group.

Notes

1. Negative period is indicative of retrograde motion.
2. Osculating orbital parameters of irregular satellites of Jupiter change widely in short intervals due to heavy perturbation by the Sun. For example, changes of as much as 1 Gm in semi-major axis in 2 years, 0.5 in eccentricity in 12 years, and as much as 5° in 24 years have been reported. Mean orbital elements are the averages calculated by the numerical integration of current elements over a long period of time, used to determine the dynamical families.
3. With the exception of Kalyke, which is substantially redder.