Animation of Saturn's Inuit group of satellites Kiviuq·Ijiraq·Paaliaq·Siarnaq·TarqeqDiagram 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 progradeirregular 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 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
The thirty-six known members of the Inuit group are (sorted by date announcement):
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