Helene (moon)
Cassini image of Helene against the backdrop of Saturn's clouds (March 3, 2010)
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Discovery | |
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Discovered by | Laques and Lecacheux |
Discovery site | Pic du Midi Observatory |
Discovery date | March 1, 1980 |
Designations | |
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Orbital characteristics | |
377396 km | |
Eccentricity | 0.0022 |
2.736915 d [1] | |
Inclination | 0.199° (to Saturn's equator) |
Satellite of | <templatestyles src="Plainlist/styles.css"/> |
Physical characteristics | |
Dimensions | 43.4 × 38.2 × 26 km [2] |
Mean radius
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17.6±0.4 km [2] |
Albedo | 1.67±0.20 (geometric) [3] |
Helene (/ˈhɛlᵻniː/ HEL-ə-nee;[lower-alpha 1] 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.[4] In 1988 it was officially named after Helen of Troy, who was the granddaughter of Cronus (Saturn) in Greek mythology.[5] Helene is also designated Saturn XII (12), which it was given in 1982, and Dione B,[lower-alpha 2] because it is co-orbital with Dione and located in its leading Lagrangian point (L4). It is one of four known trojan moons.
Exploration
Helene was initially observed from Earth in 1980,[4] and Voyager flybys of Saturn in the early 1980s allowed much closer views. The Cassini–Huygens mission, which went into orbit around Saturn in 2004, provided still better views, and allowed more in-depth analysis of Helene, including views of the surface under different lighting conditions. Some of the closest images of Helene to date are from the Cassini spacecraft's 1800 km flyby on March 3, 2010, and another very successful imaging sequence occurred in June 2011. There have been many other approaches over the course of the Cassini mission, and future flybys may yield additional data.
Selected observations
Mostly raw greyscale images with near infrared or ultraviolet channels.
References
Notes
- ↑ /ˈhɛlᵻniː/ HEL-ə-nee is the regular pronunciation, as expected from the Greek etymology, but /hᵻˈliːniː/ hə-LEE-nee and /hᵻˈliːn/ hə-LEEN are also heard. The Modern Greek pronunciation is e-LAY-nee.
- ↑ Transactions of the International Astronomical Union, Vol. XVIIIA, 1982 (mentioned in IAUC 3872: Satellites of Jupiter and Saturn, September 30, 1983)
Citations
Sources
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External links
Wikimedia Commons has media related to Helene. |
- Helene Profile[dead link] by NASA's Solar System Exploration; see instead Cassini Solstice Mission: Helene
- The Planetary Society: Helene
- Helene has two faces—The Planetary Society : Helene Mini Atlas—Mar. 11, 2010
- Cassini catches Helene—The Planetary Society : Video & Views—Jun. 20, 2011