Polydeuces
Saturn's moon Polydeuces

Saturn's moon 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[1]
Inclination 0.1774 ± 0.0015°[2]
Is a satellite of Saturn
Physical characteristics
Mean diameter 3.5 km[3]
Mass 1 − 5 ×1013 kg [4]
Mean density unknown
Surface gravity unknown
Rotation period assumed synchronous
Axial tilt unknown
Albedo unknown
Surface temperature
min mean max
Atmosphere none

Polydeuces (Template:PronEng 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.[3]

Polydeuces was discovered by the Cassini Imaging Team on October 24, 2004[5] in images taken on October 21, 2004,[6],[3] 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[5]. Polydeuces is also designated as Saturn XXXIV.

Of the known Lagrangian co-orbitals in the Saturn system, Polydeuces wanders the farthest 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°).[2] 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.[5]

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.

References[edit]

  1. ^ a b The mean semi-major axis and period must be identical to Dione's.
  2. ^ a b c Spitale, J. N. (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal. 132 (2): 692. doi:10.1086/505206.  Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ a b c Porco, 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 Cite error: Invalid <ref> tag; name "Porco" defined multiple times with different content (see the help page).
  4. ^ based on density 0.5 − 2 g/cm³
  5. ^ a b c Murray, C. D.; et al. (2005). "S/2004 S 5: A new co-orbital companion for Dione". Icarus. 179: 222. doi:10.1016/j.icarus.2005.06.009. 
  6. ^ C.C. Porco, et al., IAUC 8432: Satellites and Rings of Saturn November 8, 2004 (discovery)
  7. ^ IAUC 8471: Satellites of Saturn January 21, 2005 (naming the moon)

External links[edit]