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.

Their semi-major axes (distances from Jupiter) range between 22.9 and 24.1 Gm, their orbital inclinations between 164.9° and 165.5°, and their orbital eccentricities between 0.23 and 0.27 (with one exception).

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.

The core members include (negative period indicates retrograde orbit):[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)	Period (days)	Notes
Carme	46.7	−756.09	largest member and group prototype
Taygete	5	−691.62
Eukelade[3]	4	−735.03
Eirene[3]	3	−739.53
Chaldene	4	−691.25
Isonoe	4	−727.65
Kalyke	6.9	−697.41	substantially redder than the others
Erinome	3	−739.53
Aitne	3	−727.95
Kale	2	−685.07
Pasithee	2	−699.28
S/2003 J 9 (probably)[3]	1	−767.60

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

Origin

The very low dispersion of the mean¹ orbital elements among the core members (the group is separated by less than 700,000 km in semi major axis and less than 0.7° 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).[4] 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.[5]

Further support to the single body origin comes from the known colours: all² the satellites appear light red, with colour indices B-V= 0.76 and V-R= 0.47[6] and infrared spectra, similar to D-type asteroids.[7] These data are consistent with a progenitor from the Hilda family or a Jupiter Trojan.

¹Osculating orbital parameters of irregular satellites of Jupiter change widely in short intervals due to heavy perturbation by Jupiter. 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.
²With the exception of Kalyke, substantially redder.

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 (see related diagram).

This diagram shows the compactness of the Carme group.

References

1. Scott S. Sheppard, David C. Jewitt, Carolyn Porco Jupiter's outer satellites and Trojans, In: Jupiter. The planet, satellites and magnetosphere. Edited by Fran Bagenal, Timothy E. Dowling, William B. McKinnon. Cambridge planetary science, Vol. 1, Cambridge, UK: Cambridge University Press, ISBN 0-521-81808-7, 2004, p. 263 - 280 Full text(pdf). Archived June 14, 2007, at the Wayback Machine
2. David Nesvorný, Cristian Beaugé, and Luke Dones Collisional Origin of Families of Irregular Satellites, The Astronomical Journal, 127 (2004), pp. 1768–1783 Full text.
3. Listed by Nesvorný 2004 as a possible member, not listed by Sheppard 2004; the orbital elements confirmed by Jacobson 2004
4. David Nesvorný, Jose L. A. Alvarellos, Luke Dones, and Harold F. Levison Orbital and Collisional Evolution of the Irregular Satellites, The Astronomical Journal,126 (2003), pages 398–429. (pdf)
5. Sheppard, Scott S.; Jewitt, David C. (May 5, 2003). "An abundant population of small irregular satellites around Jupiter". Nature. 423 (6937): 261–263. Bibcode:2003Natur.423..261S. doi:10.1038/nature01584. PMID 12748634. S2CID 4424447.
6. Grav, Tommy; Holman, Matthew J.; Gladman, Brett J.; Aksnes, Kaare Photometric survey of the irregular satellites, Icarus, 166,(2003), pp. 33-45. Preprint
7. Tommy Grav and Matthew J. Holman Near-Infrared Photometry of the Irregular Satellites of Jupiter and Saturn,The Astrophysical Journal, 605, (2004), pp. L141–L144 Preprint