Polydeuces (moon)

Polydeuces (pronEng|ˌpɒlɨˈdjuːsiːz respell|POL|i|DEW|seez, or as Greek "Πολυδεύκης)" is a very small natural satellite of Saturn that is co-orbital with Dione and librates around the trailing Lagrangian point (L₅). Its diameter is estimated to be about 3.5 km.

Polydeuces was discovered by the [http://ciclops.org/team/iss_team.php Cassini Imaging Team] on October 24, 2004cite journal | author= Murray, C. D.; "et al."| title= "S/2004 S 5: A new co-orbital companion for Dione"| journal= Icarus| year= 2005| volume= 179| pages= 222| doi= 10.1016/j.icarus.2005.06.009] in images taken on October 21, 2004^, [ [http://cfa-www.harvard.edu/iauc/08400/08432.html C.C. Porco, et al., IAUC 8432: "Satellites and Rings of Saturn"] 2004 November 8 (discovery)] ^,Porco, C. C.; "et al." (2005), [http://www.sciencemag.org/cgi/content/short/307/5713/1226 "Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites"] , Science, Vol. 307, No. 5713, pp. 1226-1236] and given the temporary designation S/2004 S 5. Subsequent searches of earlier Cassini imaging showed it in images as far back as April 9, 2004. Polydeuces is also designated as Saturn XXXIV.

Of the known Lagrangian co-orbitals in the Saturn system, Polydeuces wanders the furtherest from its Lagrangian point. The libration takes it away from the L₅ by up to 31.4° in the direction away from Dione, and 26.1° towards it with a period of 790.931 days (for comparison L₅ trails Dione by 60°). Polydeuces' libration is large enough that it takes on some qualities of a tadpole orbit, as evidenced by the clear asymmetry between excursions towards and away from Dione. In the course of one such cycle, Polydeuces' orbital radius also varies by about ± 7660 km with respect to Dione's.

The name Polydeuces was approved by the IAU Working Group on Planetary System Nomenclature on January 21, 2005. [ [http://cfa-www.harvard.edu/iauc/08400/08471.html IAUC 8471: "Satellites of Saturn"] 2005 January 21 (naming the moon)] In Greek mythology, Polydeuces is another name for Pollux, twin brother of Castor, son of Zeus and Leda.

References

External links

* [http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Polydeuces Polydeuces Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.iau.org/ IAU] [http://planetarynames.wr.usgs.gov/ Working Group on Planetary System Nomenclature]
* [http://spaceflightnow.com/cassini/050224science.html Cassini news release on ring and moon discoveries, via Spaceflight Now] (February 24, 2005)