S/2004 S 6
The English used in this This is a highly technical article which needs simplification or section may not be easy for everybody to understand. (April 2012)
object seen on 21 June, 2005 by Cassini, thought to be S/2004 S 6
|Discovered by||Cassini Imaging Science Team|
|Discovered on||28 October, 2004|
|Epoch 13 April 2005 (JD 2453474.1)|
|Semimajor axis||140,134 ± 2 km|
|Eccentricity||0.00200 ± 0.00004|
|Revolution period||0.6180116 ± 0.0000004 d|
to Saturn's equator
|0.002 ± 0.001°|
|Is a satellite of||Saturn|
|Mean diameter||< 5 km |
|Rotation period||probably synchronous|
It was first seen by scientists in pictures taken by the Cassini-Huygens probe on October 28, 2004, and announced on 8 November that year. It appears to be the best tracked object in this area with at least five possible sightings in the period till late 2005. In comparison, two objects in the F ring's area (S/2004 S 3 and S/2004 S 4) that were first seen months earlier have not been found again with any confidence. Nevertheless, it continues to be unclear whether there is a solid core to S/2004 S 6 or whether it is just a dust clump that will disappear in years or months. Notably, an imaging sequence covering an entire orbital period at 4 km resolution taken on 15 November, 2004 (soon after S/2004 S 6's discovery) failed to find the object, while it has been seen again later. The lighting conditions in S/2004 S 6's part of the orbit were different during these two sightings, however, with the discovery being made when the area was strongly backlit by the sun. A suggested resolution of the absence in November is that S/2004 S 6's visibility is primarily due to a diffuse cloud of fine dust that is much brighter in forward scattered light (the conditions of the discovery image), and that the solid core (if any) is small.
S/2004 S 6 has been seen both inside and outside the main F ring, and its orbit must cross the ring. Careful calculations show that the object periodically plows through the ring material, coming within 1.5 km of the densest core e.g. on 9 April, 2005. It has been suggested that a spiral structure in the thinnest material around the F ring may have been a result of this.
The dusty halo seen in pictures is big, being around 2000 km in lengthwise extent. The solid object, if any, would be no bigger than 3−5 km in diameter based on brightness.
References[change | change source]
- Spitale, J. N.; et al. (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal. 132: 692.
- IAUC 8432: Satellites and Rings of Saturn 2004 November 8 (claiming recovery of S/2004 S 3 on 17 October, 2004, in conflict with the later (2006) Spitale et al.)
- Charnoz, S.; et al. (2005). "Cassini Discovers a Kinematic Spiral Ring Around Saturn". Science. 310: 1300.