Polydeuces (moon)
 Saturn's moon Polydeuces |
|
| Discovery | |
|---|---|
| Discovered by | Cassini Imaging Science Team |
| Discovery date | October 24, 2004 |
| Designations | |
| Pronunciation | /ˌpɒlɨˈdjuːsiːz/ POL-i-DEW-seez |
| Alternative names | Saturn XXXIV (34) S/2004 S5 |
| Orbital characteristics [1] | |
| 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 |
| Physical characteristics | |
| Dimensions | 3 × 2.5 × 2 km[2] |
| Mean radius | 1.3 ± 0.4 km[2] |
| Mass | 1–5 ×1013 kg [b] |
| Rotation period | assumed synchronous |
Polydeuces, or Saturn XXXIV (34), is a small natural satellite of Saturn that is co-orbital with the moon Dione and librates around its trailing Lagrangian point (L5). Its diameter is estimated to be 2–3 km.[2] It is pronounced /ˌpɒlɨˈdjuːsiːz/ POL-i-DEW-seez; Greek: Πολυδεύκης. Dione's other co-orbital moon is Helene, which is bigger and located at the leading L4 point.[3]
Polydeuces was discovered by the Cassini Imaging Team on October 24, 2004,[4] in images taken on October 21, 2004,[5][6] 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.[4] Of the four known Lagrangian co-orbitals in the Saturn system ('trojan moon'), 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's 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's orbital radius also varies by about ± 7660 km with respect to Dione's.[4]
The name Polydeuces was approved by the IAU Working Group on Planetary System Nomenclature on January 21, 2005.[7] In Greek mythology, Polydeuces is another name for Pollux, twin brother of Castor, son of Zeus and Leda.
Contents |
Notes[edit]
See also[edit]
References[edit]
- ^ a b c d Spitale Jacobson et al. 2006.
- ^ a b c Thomas, P. C. (July 2010). "Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission". Icarus 208 (1): 395–401. Bibcode:2010Icar..208..395T. doi:10.1016/j.icarus.2010.01.025.
- ^ Patrick Moore, Robin Rees - Patrick Moore's Data Book of Astronomy (2011) - Page 214
- ^ a b c Murray Cooper et al. 2005.
- ^ Porco Baker et al. 2005.
- ^ IAUC 8432.
- ^ IAUC 8471.
Further reading[edit]
- Green, Daniel W. E. (November 8, 2004). "Satellites and Rings of Saturn" (discovery). IAU Circular 8432. Retrieved 2011-12-31.
- Green, Daniel W. E. (January 21, 2005). "Satellites of Saturn" (naming the moon). IAU Circular 8471. 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.
External links[edit]
- 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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