Gallic group

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Animation of Saturn's Gallic group of satellites   Saturn    Albiorix  ·    Bebhionn  ·    Erriapus  ·    Tarvos
Hill radius
.

The Gallic group is a dynamical grouping of the

inclinations between 36° and 41°, and their eccentricities between 0.46 and 0.53. The International Astronomical Union (IAU) reserves names taken from Gallic mythology
for these moons.

Similar mean orbital elements led the discoverers to postulate a common origin for the group in a breakup of a larger body.[1] The group was later found to be physically homogeneous, all satellites displaying light-red colour (colour indices B − V = 0.91 and V − R = 0.48)[2] and similar infrared indices.[3]

Remarkably, recent observations revealed that the largest member of the group, Albiorix, actually displays 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.[4] Such an impact would require a body with the diameter in excess of 1.25 km and relative velocity of 4.79 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.

The discovery of 20 new moons of Saturn was announced in October 2019 by a team led by Scott S. Sheppard using the Subaru Telescope at Mauna Kea. One of them, S/2004 S 24, is also prograde and of similar inclination, but it orbits much further away from Saturn than the other Gallic moons. This moon will nevertheless also receive a name from Gallic mythology.[5]

The seventeen members of the group are (in order by date announcement):[6]

Name Diameter (km) Semi-Major Axis (km) Period (days) Subgroup[7]
Tarvos 16 18215600 926.43 Albiorix
Erriapus 12 17507000 871.09 Albiorix
Albiorix 28.6 16329100 783.46 Albiorix
Bebhionn 7 17027200 834.85 Albiorix
S/2004 S 24[a] 3 23339000 1341.34 Outlier
S/2004 S 29
 5 17064100 837.78 Albiorix
S/2020 S 4 3 18236000 926.96 Albiorix
S/2006 S 12 4 19569800 1035.06 Albiorix
S/2007 S 8 4 17049000 836.90 Albiorix
S/2005 S 7 3 18502500 939.75 Albiorix
S/2007 S 11 4 17434400 859.53 Albiorix
S/2019 S 29 3 17353900 853.62 Albiorix
S/2019 S 31 3 17739100 882.24 Albiorix
S/2019 S 34 3 18446800 935.45 Albiorix
S/2020 S 15 3 16729200 807.82 Albiorix
S/2023 S 17 3 17385300 855.94 Albiorix
S/2023 S 18 3 17381700 855.65 Albiorix

See also

Notes

  1. ^ Its orbital elements are identical to the other moons in the Gallic group. However, it is more distant

References

  1. S2CID 4420031
    .
  2. S2CID 7793999
    .
  3. S2CID 15665146
    .
  4. doi:10.1016/j.icarus.2007.04.020
    .
  5. ^ NASA (October 7, 2019). "Saturn surpasses Jupiter after the discovery of 20 new moons—and you can help name them". phys.org.
  6. ^ "Planetary Satellite Mean Orbital Parameters". Jet Propulsion Laboratory. Retrieved 7 June 2023.
  7. ^ "Orbital and dynamical data for solar system planets and satellites". Wm. Robert Johnston. Retrieved 17 April 2025.
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