Pallene (moon)
Pallene in September 2010
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Discovery
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| Discovered by | CICLOPS Team [1] |
| Discovery date | June 1, 2004 |
| Epoch June 20, 2004 (JD 2453177.5) | |
| Semi-major axis | 212,280 ± 5 km |
| Eccentricity | 0.0040 |
| Orbital period | 1.153745829 d [3] |
| Inclination | 0.1810 ± 0.0014° (to Saturn's equator) |
| Satellite of | Saturn |
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Physical characteristics
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| Dimensions | 2.9×2.8×2.0 km [4] |
| Mean radius | 2.5 ± 0.6 km [4] |
| Rotation period | synchronous |
| Axial tilt | zero |
Pallene (
/pəˈliːniː/ pə-LEE-nee; Greek: Παλλήνη) is a very small natural satellite of Saturn. It is one of three small moons known as the Alkyonides that lie between the orbits of the larger Mimas and Enceladus. It is also designated as Saturn XXXIII.
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[edit] Discovery
Pallene was discovered by the Cassini Imaging Team in 2004, during the Cassini–Huygens mission.[5][6] It was given the temporary designation S/2004 S 2. In 2005, the name Pallene was provisionally approved by the IAU Division III Working Group for Planetary System Nomenclature,[7] and was ratified at the IAU General Assembly in 2006. The name refers to Pallene, one of the Alkyonides, the seven beautiful daughters of the giant Alkyoneus.
After the discovery in 2004, it was realized that Pallene had been first photographed on August 23, 1981, by the space probe Voyager 2. It had appeared in a single photograph and had been provisionally named S/1981 S 14 and estimated to orbit 200,000 km from Saturn.[8] Since it had not been visible in other images, it had not been possible to compute its orbit at the time, but recent comparisons have shown it to match Pallene's orbit.[2]
[edit] Orbital characteristics
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°.[2]
[edit] Ring
In 2006, images taken in forward-scattered light by the Cassini spacecraft enabled the Cassini Imaging Team to discover a faint dust ring around Saturn that shares Pallene's orbit, now named the Pallene Ring.[9][10] The ring has a radial extent of about 2,500 km. Its source is particles blasted off Pallene's surface by meteoroid impacts, which then form a diffuse ring around its orbital path.[a][11]
[edit] Exploration
The Cassini–Huygens spacecraft, which is currently studying Saturn and its moons, performed a fly-by of Pallene on 16 October 2010, at a distance of 36,000 kilometeres (22,000 miles).
[edit] References
Explanatory
- ^ Early press releases of the discovery mentioned the first person to see the moon in Cassini images. This bit of trivia was blown out of proportion in the following months, with this individual being credited as the "discoverer" by some sources. Because the discovery was a large team effort, involving tens of people and hundreds of hours of distributed work, a conscious decision was made by the IAU to officially and correctly assign any credit to "the Cassini Imaging team" and to avoid unfairly singling out any one individual as the discoverer.
Citations
Sources
- "Cassini Imaging Science Team". Cassini Imaging Central Laboratory for OPerationS. http://ciclops.org/team/iss_team.php. Retrieved 2012-01-01.
- "Moonmade Rings". Cassini Imaging Central Laboratory for OPerationS. October 11, 2006. http://ciclops.org/view.php?id=2276. Retrieved 2012-01-01.
- Green, Daniel W. E. (April 14, 1995). "Possible Satellites of Saturn". IAU Circular 6162. http://www.cbat.eps.harvard.edu/iauc/06100/06162.html. Retrieved 2012-01-01.
- Green, Daniel W. E. (August 16, 2004). "S/2004 S 1 and S/2004 S 2" (discovery). IAU Circular 8389. http://www.cbat.eps.harvard.edu/iauc/08300/08389.html. Retrieved 2012-01-01.
- Green, Daniel W. E. (January 21, 2005). "S/2004 S 1 and S/2004 S 2" (naming the moon). IAU Circular 8471. http://www.cbat.eps.harvard.edu/iauc/08400/08471.html. Retrieved 2012-01-01.
- Green, Daniel W. E. (October 11, 2006). "Rings of Saturn (R/2006 S 1, R/2006 S 2, R/2006 S 3, R/2006 S 4)". IAU Circular 8759. http://www.cbat.eps.harvard.edu/iauc/08700/08759.html. Retrieved 2012-01-01.
- "NASA Finds Saturn's Moons May Be Creating New Rings". Cassini Solstice Mission. JPL/NASA. October 11, 2006. http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20061011-3/. Retrieved 2012-01-01.
- Porco, C. C.; Baker, E.; Barbara, J.; Beurle, K.; Brahic, A.; Burns, J. A.; Charnoz, S.; Cooper, N. et al (February 25, 2005). "Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites". Science 307 (5713): 1226–1236. doi:10.1126/science.1108056. PMID 15731439.
- Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M., Jr. (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal 132 (2): 692–710. Bibcode 2006AJ....132..692S. doi:10.1086/505206.
- Thomas, P. C. (July 2010). "Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission". Icarus 208 (1): 395–401. Bibcode 2010Icar..208..395T. doi:10.1016/j.icarus.2010.01.025. http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf.
[edit] External links
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Wikimedia Commons has media related to: Pallene |
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