Polydeuces (moon)
Saturn's moon Polydeuces
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Discovery
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| Discovered by | Cassini Imaging Science Team |
| Discovery date | October 24, 2004 |
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Designations
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| Pronunciation |  /ˌpɒlɨˈdjuːsiːz/ POL-i-DEW-seez, or as Greek: Πολυδεύκης |
| Semi-major axis | 377,396 km [a] |
| Eccentricity | 0.0192 [1] |
| Orbital period | 2.736915 d [a] |
| Inclination | 0.1774 ± 0.0015° [1] |
| Satellite of | Saturn |
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Physical characteristics
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| Mean radius | 1.75 km [2] |
| Mass | 1 − 5 ×1013 kg [b] |
| Mean density | unknown |
| Equatorial surface gravity | unknown |
| Rotation period | assumed synchronous |
| Axial tilt | unknown |
| Albedo | unknown |
Polydeuces ( /ˌpɒlɨˈdjuːsiːz/ POL-i-DEW-seez; 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.[2]
Polydeuces was discovered by the Cassini Imaging Team on October 24, 2004,[3] in images taken on October 21, 2004,[2][4] 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.[3] Polydeuces is also designated as Saturn XXXIV.
Of the four known Lagrangian co-orbitals in the Saturn system, Polydeuces wanders the farthest from its Lagrangian point: its distance behind Dione varies from 33.9° to 91.4° with a period of 790.931 days (for comparison, L5 trails Dione by 60°).[1] 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.[3]
The name Polydeuces was approved by the IAU Working Group on Planetary System Nomenclature on January 21, 2005.[5] In Greek mythology, Polydeuces is another name for Pollux, twin brother of Castor, son of Zeus and Leda.
[edit] References
Explanatory
Citations
Sources
- Green, Daniel W. E. (November 8, 2004). "Satellites and Rings of Saturn" (discovery). IAU Circular 8432. http://www.cbat.eps.harvard.edu/iauc/08400/08432.html. Retrieved 2011-12-31.
- Green, Daniel W. E. (January 21, 2005). "Satellites of Saturn" (naming the moon). IAU Circular 8471. http://www.cbat.eps.harvard.edu/iauc/08400/08471.html. Retrieved 2011-12-31.
- Murray, C. D.; Cooper, N. J.; Evans, M. W.; Beurle, K. (December 1, 2005). "S/2004 S 5: A new co-orbital companion for Dione". Icarus 179 (1): 222–234. Bibcode 2005Icar..179..222M. doi:10.1016/j.icarus.2005.06.009.
- Porco, C. C.; Baker, E.; Barbara, J.; Beurle, K.; Brahic, A.; Burns, J. A.; Charnoz, S.; Cooper, N. et al (February 25, 2005). "Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites". Science 307 (5713): 1226–1236. doi:10.1126/science.1108056. PMID 15731439.
- Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M., Jr. (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal 132 (2): 692–710. Bibcode 2006AJ....132..692S. doi:10.1086/505206.
[edit] External links
- Polydeuces Profile by NASA's Solar System Exploration
- IAU Working Group on Planetary System Nomenclature
- Cassini news release on ring and moon discoveries, via Spaceflight Now (February 24, 2005)
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