Saturn's Gallic group of satellites
The Gallic group is a dynamical grouping of the prograde irregular satellites of Saturn following similar orbits. Their semi-major axes range between 16 and 19 Gm, their inclinations between 35° and 40°, and their eccentricities around 0.53.
Similar mean orbital elements led the discoverers to postulate a common origin for the group in a breakup of a larger body.
The four members of the group are (in order of increasing distance from Saturn):
Remarkably, recent observations revealed that the largest member of the group, Albiorix, displays actually two different colours: one compatible with Erriapus and Tarvos, and another less red. Instead of the common progenitor, it was postulated that Tarvos and Erriapus could be fragments of Albiorix, leaving a large, less red crater. Such an impact would require a body with the diameter in excess of 1 km and relative velocity close to 5 km/s, resulting in a large crater with the radius of 12 km. Numerous, very large craters observed on Phoebe, prove the existence of such collisions in the Saturnian system's past.
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- Grav, Tommy; Holman, Matthew J.; Gladman, Brett J.; Aksnes, Kaare (2003). "Photometric survey of the irregular satellites". Icarus. 166: 33–45. arXiv:astro-ph/0301016. Bibcode:2003Icar..166...33G. doi:10.1016/j.icarus.2003.07.005.
- Grav, Tommy; Holman, Matthew J (2004). "Near-Infrared Photometry of the Irregular Satellites of Jupiter and Saturn". The Astrophysical Journal. 605: L141–L144. arXiv:astro-ph/0312571. Bibcode:2004ApJ...605L.141G. doi:10.1086/420881.
- Grav, Tommy; and Bauer, James; A deeper look at the colors of Saturnian irregular satellites, Preprint