Helene (pronounced /ˈhɛlɨniː/ HEL-ə-nee, sometimes /hɨˈliːniː/ hə-LEE-nee, or as in Greek Ἑλένη) is a moon of Saturn. It was discovered by Pierre Laques and Jean Lecacheux in 1980 from ground-based observations at Pic du Midi Observatory, and was designated S/1980 S 6.[3] In 1988 it was officially named after Helen of Troy, who was the granddaughter of Cronus (Saturn) in Greek mythology.[4]
| Helene | |
 |
|
| Discovery | |
|---|---|
| Discovered by | Laques and Lecacheux |
| Discovered in | March 1, 1980 |
| Orbital characteristics | |
| Semimajor axis | 377,396 km |
| Eccentricity | 0.0022 |
| Orbital period | 2.736915 d [1] |
| Inclination | 0.199° (to Saturn's equator) |
| Satellite of | Saturn |
| Physical characteristics | |
| Mean diameter | 32 km (36 × 32 × 30) |
| Mass | ?kg |
| Mean density | ? g/cm3 |
| Surface gravity | ?m/s2 |
| Escape velocity | ?km/s |
| Rotation period | assumed synchronous |
| Axial tilt | zero |
| Albedo | ? |
| Surface temperature | ? K |
| Atmosphere | none |
The moon is also designated Saturn XII, a number which it received in 1982, under the designation Dione B,[5] because it is co-orbital with Dione and located in its leading Lagrangian point (L4). It is one of four known trojan moons.
Exploration
The closest images of Helene are from the Cassini spacecraft's 1800 km flyby on March 3, 2010.
Voyager 2 image (August 1981)
References
1. ^ NASA Celestia
2. ^ Verbiscer, A.; French, R.; Showalter, M.; Helfenstein, P. (2007). "Enceladus: Cosmic Graffiti Artist Caught in the Act". Science 315: 815. doi:10.1126/science.1134681. p. 815 (supporting online material, table S1)
3. ^ IAUC 3496: Satellites of Saturn 1980 July 31 (discovery)
4. ^ IAUC 4609: Satellites of Saturn and Uranus 1988 June 8 (naming the moon)
5. ^ Transactions of the International Astronomical Union, Vol. XVIIIA, 1982 (mentioned in IAUC 3872: Satellites of Jupiter and Saturn, 1983 September 30)
External links
* Helene Profile by NASA's Solar System Exploration
* The Planetary Society: Helene
* Helene has two faces - The Planetary Society : Helene Mini Atlas - Mar. 11, 2010
... | Telesto, Tethys, Calypso | Polydeuces, Dione, Helene | Rhea | ...
Saturn's natural satellites
Pan | Daphnis | Atlas | Prometheus | S/2004 S 6 | S/2004 S 4 | S/2004 S 3 | Pandora | Epimetheus and Janus | Mimas | Methone | Pallene | Enceladus | Telesto, Tethys, and Calypso | Polydeuces, Dione, and Helene | Rhea | Titan | Hyperion | Iapetus | Kiviuq | Ijiraq | Phoebe | Paaliaq | Skathi | Albiorix | S/2004 S 11 | Erriapo | Siarnaq | S/2004 S 13 | Tarvos | Mundilfari | S/2004 S 17 | Narvi | S/2004 S 15 | S/2004 S 10 | Suttungr | S/2004 S 12 | S/2004 S 18 | S/2004 S 9 | S/2004 S 14 | S/2004 S 7 | Thrymr | S/2004 S 16 | Ymir | S/2004 S 8
see also: Rings of Saturn | Cassini-Huygens | Themis
see also: The Solar System
Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License
