S/2004 S 6

S/2004 S 6

object seen on 21 June, 2005 by Cassini, thought to be S/2004 S 6
Discovery
Discovered by Cassini Imaging Science Team Archived 2011-05-20 at the Wayback Machine
Discovered on 28 October, 2004
Orbital characteristics
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
Inclination
to Saturn's equator		 0.002 ± 0.001°
Is a satellite of Saturn
Physical characteristics
Mean diameter < 5 km
Rotation period probably synchronous
Axial tilt unknown
Albedo unknown
Atmosphere none

S/2004 S 6 is the designation of a dusty object seen orbiting Saturn very close to the F ring. It is not clear whether it is only a clump of dust, or if there is a solid small moon at its core.

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. An imaging sequence covering an entire orbital period at 4 km resolution taken on 15 November 2004, soon after it was discovered did not 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. The discovery was made when the area was strongly backlit by the sun. S/2004 S 6's visibility may be 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. 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 length. The solid object, if any, would be no bigger than 3−5 km in diameter based on brightness.

References

  1. 1 2 3 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 (2): 692–710. Bibcode:2006AJ....132..692S. doi:10.1086/505206. S2CID 26603974.
  2. ↑ 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.)
  3. ↑ Charnoz, S.; et al. (2005). "Cassini Discovers a Kinematic Spiral Ring Around Saturn". Science. 310 (5752): 1300–1304. Bibcode:2005Sci...310.1300C. doi:10.1126/science.1119387. PMID 16311328. S2CID 6502280.