Pallene (moon)
From Wikipedia, the free encyclopedia
 Discovery image of Pallene |
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| Discovery | |
| Discovered by | Cassini Imaging Science Team |
| Discovered on | 1 June 2004 |
| Orbital characteristics [1] | |
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| Semimajor axis | 212,280 ± 5 km |
| Eccentricity | 0.0040 |
| Orbital period | 1.153745829 d |
| Inclination (to Saturn's equator) |
0.1810 ± 0.0014° |
| Is a satellite of | Saturn |
| Physical characteristics | |
| Mean diameter | ≈ 4 km |
| Mass | 1.7 − 7 ×1013 kg[2] |
| Mean density | unknown |
| Surface gravity | unknown |
| Rotation period | synchronous |
| Axial tilt | unknown |
| Albedo | unknown |
| Atmosphere | none |
Pallene (pə-lee'-nee, IPA: [pəˈliːni], Greek Παλλήνη) is a very small natural satellite of Saturn lying between the orbits of Mimas and Enceladus.
It was discovered by Sébastien Charnoz, as part of the Cassini Imaging team led by Carolyn C. Porco in 2004, and given the temporary designation S/2004 S 2. It was actually first seen on August 23, 1981 by Voyager 2 in a single photograph and named S/1981 S 14 and its distance to Saturn was then estimated at 200,000 km. Since it was not visible in other images, its orbit could not be calculated at the time, but recent comparisons have identified it as matching Pallene's orbit [1]. Pallene is also designated as Saturn XXXIII.
Pallene is visibly affected by a perturbing mean longitude resonance with the much larger Enceladus, although this effect is not as large as the Mimas perturbations on Methone. The perturbations cause Pallene's osculating orbital elements to vary with an amplitude of about 4 km in semi-major axis, and 0.02° in longitude (corresponding to about 75 km). Eccentricity also changes on various timescales between 0.002 and 0.006, and inclination between about 0.178° and 0.184° [1].
The names Methone and Pallene have been provisionally approved by the IAU Division III Working Group for Planetary System Nomenclature. They should be officially approved at the IAU General Assembly in 2006. Pallene was one of the Alkyonides, the seven beautiful daughters of the Giant Alkyoneus.
A faint dust ring shares Pallene's orbit, as revealed by images taken in forward-scattered light by the Cassini spacecraft in 2006 [3]. The ring has a radial extent of about 2,500 km. Its source are particles blasted off Pallene's surface by meteoroid impacts, which then form a diffuse ring around its orbital path [4].
[edit] External links
[edit] References
- ^ a b c J.N. Spitale et al (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal 132: 692.
- ^ Based on density 0.5 - 2 g/cm³
- ^ NASA Planetary Photojournal PIA08328: Moon-Made Rings
- ^ Cassini-Huygens press release NASA Finds Saturn's Moons May Be Creating New Rings, 11 October 2006.
- C.C. Porco et al (2005). "Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites". Science 307 (5713): 1226-1236. (February 25, 2005; subscription required)
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Generally listed in increasing distance from Saturn
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| Ring shepherds | Pan · Daphnis · Atlas · Prometheus · S/2004 S 6? · S/2004 S 4? · S/2004 S 3? · Pandora |
| Co-orbitals | Epimetheus · Janus |
| Inner large and Trojan | Mimas · Methone · Pallene · Enceladus · Tethys (trojans Telesto, Calypso) · Dione (trojans Helene, Polydeuces) |
| Outer large | Rhea · Titan · Hyperion · Iapetus |
| Inuit group | Kiviuq · Ijiraq · Paaliaq · Siarnaq |
| Norse group | Phoebe · Skathi · Skoll · S/2004 S 13 · S/2006 S 4 · Hyrokkin · Mundilfari · S/2006 S 6 · S/2006 S 1 · S/2004 S 17 · Narvi · Bergelmir · Aegir · Suttungr · S/2004 S 12 · Bestla · Farbauti · Hati · S/2004 S 7 · Thrymr · S/2006 S 3 · Surtur · Kari · Fenrir · Ymir · Loge · Fornjot |
| Gallic group | Albiorix · Bebhionn · Erriapo · Tarvos |
