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Inuit group

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Animation of Saturn's Inuit group of satellites
   Kiviuq ·    Ijiraq ·    Paaliaq ·    Siarnaq ·   Tarqeq
Diagram illustrating the orbits of the irregular satellites of Saturn, showing the three Inuit subgroups. The inclination and semi-major axis are represented on the Y and X-axis, respectively. The satellites with inclinations below 90° are prograde, those above 90° are retrograde. The X-axis is labeled in terms of Saturn's Hill radius.

The Inuit group is a dynamical grouping of prograde irregular satellites of Saturn which follow similar orbits. Although almost all irregular moons are believed to have originated from a captured asteroid that later got involved in a collision, it is not currently known whether all the members in the Inuit group originated from a single progenitor, though the moons with measured colours appear similar to each other. Within the Inuit group, there are three clusterings or subgroups, each associated with a moon (Kiviuq, Paaliaq, and Siarnaq) and a distinct semi-major axis. It is unclear how a collisional family could have ended up with as large of a spread in semi-major axis as the Inuit group is, however, the probability of three unrelated clusters having a similar inclination by coincidence is low.[1]

The International Astronomical Union (IAU) uses names taken from Inuit mythology for these moons, though only five of them have names at present.

Characteristics

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The group appeared quite homogeneous in early observations, the satellites displaying light-red colour (colour indices B−V = 0.79 and V−R = 0.51, similar to that of the Gallic group)[2] and similar infrared spectra.[3] Later observations, however, revealed that Ijiraq is distinctly redder than Paaliaq, Siarnaq and Kiviuq. In addition, unlike the other three, Ijiraq's spectrum does not display weak absorption near 0.7 μm. This feature is attributed to a possible water hydration.[4]

The spectral homogeneity (with the exception of Ijiraq) is consistent with a common origin in the break-up of a single object but the dispersion of the orbital parameters requires further explanation. Secular resonances among the members could provide the explanation of the post-collisional dispersion.

The Inuit group members have semi-major axes range between 11 and 19 million km, their inclinations between 43° and 51°, and their eccentricities between 0.08 and 0.39. They take an average of 2 years to orbit Saturn. There are 36 moons total, of which 20 reside in the Kiviuq subgroup and 15 in the Siarnaq subgroup. The Kiviuq subgroup is a confirmed collisional family[5] and their semi-major axes are lower and range between 11 million km and 13 million km, inclinations between 44° and 51°, and have higher eccentricities between 0.25 and 0.39. The Siarnaq subgroup has 15 members and have higher semi-major axes between 17 million km and 19 million km, inclinations between 43° and 49°, and eccentricities between 0.08 and 0.31. Paaliaq is by itself and orbits at a distance in between the two other subgroups.

List

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The thirty-six known members of the Inuit group are (sorted by date announcement):

Name Diameter (Km) Semi-Major Axis (Km) Period (days)[6] Subgroup
Paaliaq 30 14997900 686.94 Paaliaq
Siarnaq 39.3 17881100 895.58 Siarnaq
Kiviuq 19 11307500 449.13 Kiviuq
Ijiraq 15 11344600 451.43 Kiviuq
Tarqeq 7 17751000 884.99 Siarnaq
S/2004 S 31 5 17497200 866.09 Siarnaq
S/2019 S 1 5 11245400 445.51 Kiviuq
S/2020 S 1 4 11338600 451.10 Kiviuq
S/2020 S 3 3 18057200 908.19 Siarnaq
S/2020 S 5 3 18391400 933.89 Siarnaq
S/2019 S 6 4 18205500 919.71 Siarnaq
S/2005 S 4 5 11324500 450.22 Kiviuq
S/2019 S 14 4 17853200 893.14 Siarnaq
S/2004 S 54 4 11277500 447.14 Kiviuq
S/2004 S 55 3 11294700 448.16 Kiviuq
S/2004 S 58 5 18254500 920.80 Siarnaq
S/2005 S 6 4 18107300 909.58 Siarnaq
S/2006 S 23 3 18269700 921.86 Siarnaq
S/2007 S 10 4 11364900 452.36 Kiviuq
S/2019 S 22 3 11305100 448.48 Kiviuq
S/2019 S 23 3 11310200 449.08 Kiviuq
S/2019 S 24 4 11360500 452.07 Kiviuq
S/2019 S 25 4 11329400 450.22 Kiviuq
S/2019 S 26 3 11390900 453.89 Kiviuq
S/2019 S 32 5 17960500 898.71 Siarnaq
S/2020 S 11 3 11295600 448.21 Kiviuq
S/2020 S 12 3 11314500 449.33 Kiviuq
S/2020 S 13 3 11415600 455.39 Kiviuq
S/2020 S 19 3 17726700 881.04 Siarnaq
S/2023 S 1 3 11205400 442.86 Kiviuq
S/2023 S 2 3 11309900 449.05 Kiviuq
S/2023 S 3 3 17646400 875.00 Siarnaq
S/2023 S 6 3 11953100 487.91 Kiviuq
S/2023 S 7 4 12133700 499.01 Kiviuq
S/2023 S 19 3 17590300 870.92 Siarnaq
S/2023 S 22 4 18577500 945.37 Siarnaq

See also

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References

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  1. ^ Ashton, Edward; Gladman, Brett; Alexandersen, Mike; Petit, Jean-Marc (2025-12-09). "Retrograde Predominance of Small Saturnian Moons Reiterates a Recent Retrograde Collisional Disruption". The Planetary Science Journal. 6 (12): 283. arXiv:2503.07081v2. doi:10.3847/PSJ/ae1d62. ISSN 2632-3338. Retrieved 2026-01-03.
  2. ^ Grav, Tommy; Holman, Matthew J.; Gladman, Brett; Aksnes, Kaare (November 2003). "Photometric Survey of the Irregular Satellites". Icarus. 166 (1): 33–45. arXiv:astro-ph/0301016. Bibcode:2003Icar..166...33G. doi:10.1016/j.icarus.2003.07.005.
  3. ^ Grav, Tommy; Holman, Matthew J. (2004-04-20). "Near-Infrared Photometry of Irregular Satellites of Jupiter and Saturn". The Astrophysical Journal. 605 (2): L141–L144. arXiv:astro-ph/0312571. Bibcode:2004ApJ...605L.141G. doi:10.1086/420881. ISSN 0004-637X.
  4. ^ Grav, Tommy; Bauer, James (2007-11-01). "A deeper look at the colors of the Saturnian irregular satellites". Icarus. 191 (1): 267–285. arXiv:astro-ph/0611590. Bibcode:2007Icar..191..267G. doi:10.1016/j.icarus.2007.04.020.
  5. ^ Ashton, Edward; Gladman, Brett; Alexandersen, Mike; Petit, Jean-Marc (2025-03-13). "Discovery of 128 New Saturnian Irregular Moons". Research Notes of the AAS. 9 (3): 57. doi:10.3847/2515-5172/adbf87. ISSN 2515-5172.
  6. ^ "Planetary Satellite Mean Elements". Jet Propulsion Laboratory. California Institute of Technology. 25 January 2024.
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Mean orbital parameters: from JPL

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