Siarnaq (moon)

Irregular satellite
ref_discovery=Discovery Circumstances [http://ssd.jpl.nasa.gov/?sat_discovery (JPL)] ]

name=Siarnaq - Saturn XXIX
discoverer=Brett J. Gladman "et al."
discovery_date=in 2000
epoch=2000 Feb. 26.00
ref_orb_elems=Mean orbital parameters [http://ssd.jpl.nasa.gov/?sat_elem from JPL] ]
semimajor=17.531
eccentricity=0.2961
inclination=46.0
period=895.55 d (2.45 yr)
diameter=40 km [http://www.ifa.hawaii.edu/~sheppard/satellites/satsatdata.html Scott Sheppard pages] ]
albedo=0.04 "assumed"
color="light red" B-V=0.87 R-V=0.48Grav, T.; and Bauer, J.; [http://arxiv.org/abs/astro-ph/0611590 "A deeper look at the colors of Saturnian irregular satellites"] ]

Siarnaq (pronEng|ˈsiːɑrnɑːk "SEE-ar-naak)," or Saturn XXIX, is a prograde irregular satellite of Saturn. It was discovered by Brett J. Gladman, et al. in 2000 [ [http://cfa-www.harvard.edu/iauc/07500/07513.html IAUC 7513: "S/2000 S 3 and S/2000 S 4"] 2000 October 25 (discovery)] , [ [http://cfa-www.harvard.edu/mpec/K00/K00Y14.html MPEC 2000-Y14: "S/2000 S 3, S/2000 S 4, S/2000 S 5, S/2000 S 6, S/2000 S 10"] 2000 December 19 (discovery and ephemeris)] and given the temporary designation S/2000 S 3.Named in August 2003 after the giant Siarnaq [ [http://cfa-www.harvard.edu/iauc/08100/08177.html IAUC 8177: "Satellites of Jupiter, Saturn, Uranus"] 2003 August 8 (naming the moon)] (also known as Sedna) in Inuit mythology, it is the largest member of the Inuit group of irregular satellites.

Siarnaq is thought to be about 40 kilometres in diameter and orbits Saturn at an average distance of 17.5 Gm in 895 days.

The diagram illustrates its orbit in relation to other prograde irregular satellites of Saturn. The eccentricity of the orbits is represented by the yellow segments extending from the pericentre to the apocentre.

Siarnaq displays light-red colours and the infrared spectrum very similar to Paaliaq and Kiviuq, supporting the thesis of a possible common origin in the break-up of a larger bodyGladman, 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.; [http://www.nature.com/nature/journal/v412/n6843/abs/412163a0.html "Discovery of 12 satellites of Saturn exhibiting orbital clustering"] , Nature, 412 (2001 July 12), pp. 163–166] Grav, T.; Holman, M. J.; Gladman, B. J.; Aksnes, K.; [http://arxiv.org/abs/astro-ph/0301016 "Photometric survey of the irregular satellites"] , Icarus, 166 (2003), pp. 33-45] .

Siarnaq has been found to be in a secular resonance with Saturn, involving the precession of its periapsis and that of the planet.
Ćuk, M.; Burns, J. A.; [http://arxiv.org/abs/astro-ph/0408119 "On the Secular Behavior of Irregular Satellites"] , The Astronomical Journal, 128 (2004), pp. 2518-2541] 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.

References

*Ephemeris [http://cfa-www.harvard.edu/iau/NatSats/NaturalSatellites.html IAU-MPC NSES]

External links

* [http://www.ifa.hawaii.edu/~jewitt/irregulars.html David Jewitt pages]
* [http://www.ifa.hawaii.edu/~sheppard/satellites/satsatdata.html Scott Sheppard pages]