Siarnaq (moon)

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Siarnaq - Saturn XXIX
Discovery [1]
Discovered by Brett J. Gladman et al.
Discovered in 2000
Mean Orbital elements [2]
Epoch 2000 Feb. 26.00
Semi-major axis 17.531 Gm
Eccentricity 0.2961
Inclination 46.0° *
Orbital period 895.55 d
(2.45 yr)
Physical characteristics
Mean diameter 40 km[3] **
Rotation period 10 h 09 m[4]
Albedo 0.04[3] assumed
Color light red
B-V=0.87 R-V=0.48[5]
Spectral type ?

*to the ecliptic

**based on the albedo

Siarnaq (/ˈsɑrnɑːk/ SEE-ar-nahk), or Saturn XXIX, is a prograde irregular satellite of Saturn. It was discovered by Brett J. Gladman, et al. in 2000,[6][7] and given the temporary designation S/2000 S 3. Named after the giant Siarnaq of Inuit mythology,[8] it is the largest member of the Inuit group of irregular satellites.

Irregular prograde groups of satellites of Saturn: Inuit (blue) and Gallic (red). The eccentricity of the orbits is represented by the yellow segments extending from the pericentre to the apocentre.

Siarnaq is thought to be about 40 kilometers in diameter. It orbits Saturn at an average distance of 17.5 Gm in 895 days. The rotation period was measured by the Cassini spacecraft to approximately 10 hours and 9 minutes;[4] this is the shortest rotation period of all prograde irregular moons of Saturn.

It is light red in color, and the Siarnaup (Siarnaqan) spectrum in the infrared is very similar to the Inuit-group satellites Paaliaq and Kiviuq, supporting the thesis of a possible common origin in the break-up of a larger body.[5][9][10]

Siarnaq has been found to be in a secular resonance with Saturn, involving the precession of its periapsis and that of the planet.[11]1 The studies of these resonances are key to understand the capture mechanism for the irregular satellites and, assuming a common origin of a given dynamical group in the break-up of a single body, to explain today’s dispersion of the orbital elements.

1The ecliptic longitudes of the periapsis of the satellite and the planet are locked.


  1. ^ Discovery Circumstances (JPL)
  2. ^ Mean orbital parameters from JPL
  3. ^ a b Scott Sheppard pages
  4. ^ a b Denk, T., Mottola, S. (2013): Irregular Saturnian Moon Lightcurves from Cassini-ISS Observations: Update. Abstract 406.08, DPS conference 2013, Denver (Colorado)
  5. ^ a b Grav, T.; and Bauer, J.; A deeper look at the colors of Saturnian irregular satellites
  6. ^ IAUC 7513: S/2000 S 3 and S/2000 S 4 October 25, 2000 (discovery)
  7. ^ MPEC 2000-Y14: S/2000 S 3, S/2000 S 4, S/2000 S 5, S/2000 S 6, S/2000 S 10 December 19, 2000 (discovery and ephemeris)
  8. ^ IAUC 8177: Satellites of Jupiter, Saturn, Uranus August 8, 2003 (naming the moon)
  9. ^ Gladman, B. J.; Nicholson, P. D.; Burns, J. A.; Kavelaars, J. J.; Marsden, B. G.; Holman, M. J.; Grav, T.; Hergenrother, C. W.; Petit, J.-M.; Jacobson, R. A.; and Gray, W. J.; Discovery of 12 satellites of Saturn exhibiting orbital clustering, Nature, 412 (July 12, 2001), pp. 163–166
  10. ^ Grav, T.; Holman, M. J.; Gladman, B. J.; Aksnes, K.; Photometric survey of the irregular satellites, Icarus, 166 (2003), pp. 33-45
  11. ^ Ćuk, M.; Burns, J. A.; On the Secular Behavior of Irregular Satellites, The Astronomical Journal, 128 (2004), pp. 2518-2541