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' Polydeuces'

Discovery
Discovered by	Cassini Imaging Science Team
Discovered on	24 October, 2004
Orbital characteristics
mean Semimajor axis	377,396 km[1]
Eccentricity	0.0192[2]
Orbital period	2.736915 d
Inclination	0.1774 ± 0.0015°
Is a satellite of	Saturn
Physical characteristics
Mean diameter	3.5 kmPorco, C. C.; ''et al.''; ''Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites'', Science, Vol. 307, No. 5713 (February 25, 2005), pp. 1226-1236
Mass	1 − 5 kg [3]
Mean density	unknown
Surface gravity	unknown
Rotation period	assumed synchronous
Axial tilt	unknown
Albedo	unknown
Surface temperature	min mean max
Atmosphere	none

'Polydeuces' ''(pol'-ee-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.
Polydeuces was discovered by the Cassini Imaging Team on October 24, 2004^[4] in images taken on October 21, 2004^,[5],Porco, C. C.; ''et al.'' (2005), ''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.^[6] In Greek mythology, Polydeuces is another name for Pollux, twin brother of Castor, son of Zeus and Leda.

Contents

References

External links

References

1. The ''mean'' semi-major axis and period must be identical to Dione's.
2. ''The orbits of Saturn's small satellites derived from combined historic and ''Cassini'' imaging observations'', Spitale, J. N., , , The Astronomical Journal, 2006
3. based on density 0.5 − 2 g/cm³
4. ''S/2004 S 5: A new co-orbital companion for Dione'', Murray, C. D.; ''et al.'', , , Icarus, 2005
5. C.C. Porco, et al., IAUC 8432: ''Satellites and Rings of Saturn'' 2004 November 8 (discovery)
6. IAUC 8471: ''Satellites of Saturn'' 2005 January 21 (naming the moon)

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)
''... | Telesto, Tethys and Calypso | Polydeuces, Dione and Helene | Rhea | ...''