Polydeuces , or Saturn XXXIV, is a small

natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

that is co-orbital with the moon Dione and librates around its trailing

Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of ...

(). Its diameter is estimated to be 2–3 km. Dione's other co-orbital moon is Helene, which is bigger and located at the leading L4 point. Polydeuces was discovered by th
Cassini Imaging Team
on October 24, 2004, in images taken on October 21, 2004, 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. 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, trails Dione by 60°). Polydeuces's libration is large enough that it takes on some qualities of a

tadpole orbit In celestial mechanics, a horseshoe orbit is a type of co-orbital motion of a small orbiting body relative to a larger orbiting body. The osculating (instantaneous) orbital period of the smaller body remains very near that of the larger body, a ...

, 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. The name Polydeuces was approved by the IAU Working Group on Planetary System Nomenclature on January 21, 2005. In

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities of de ...

, Polydeuces is another name for Pollux, twin brother of Castor, son of

Zeus Zeus or , , ; grc, Δῐός, ''Diós'', label=genitive Boeotian Aeolic and Laconian grc-dor, Δεύς, Deús ; grc, Δέος, ''Déos'', label=genitive el, Δίας, ''Días'' () is the sky and thunder god in ancient Greek religion, ...

and Leda. Due to gravitational interactions with Dione, its surface may be in

hydrostatic equilibrium In fluid mechanics, hydrostatic equilibrium (hydrostatic balance, hydrostasy) is the condition of a fluid or plastic solid at rest, which occurs when external forces, such as gravity, are balanced by a pressure-gradient force. In the planetary ...

but not its interior, similar to Methone being in hydrostatic equilibrium due to interactions with Mimas. Animation of Polydeuces's orbit relative to Saturn and Dione

Animation of Polydeuces's orbit relative to Saturn and Dione

Notes

References

External links

Polydeuces Profile
b
NASA's Solar System Exploration

IAUWorking Group on Planetary System Nomenclature

(February 24, 2005) {{DEFAULTSORT:Polydeuces (Moon) Moons of Saturn Trojan moons 20041024 Moons with a prograde orbit

See also

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Further reading

External links