S/2004 S 4

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S/2004 S 4
Discovery
Discovered by Joseph Spitale / Cassini Imaging Science Team.[1]
Discovered on 21 June, 2004
Orbital characteristics
Semimajor axis ~140,100 km.[2]
Eccentricity unknown, small
Orbital period ~0.618 d [2]
Inclination unknown, small
Is a satellite of Saturn
Physical characteristics
Mean diameter 3-5 km
Rotation period probably synchronous
Axial tilt unknown
Albedo unknown
Atmosphere none

S/2004 S 4 is the designation of an object that astronomers do not know for sure if it exists seen orbiting Saturn within the closer part of the F ring on 21 June, 2004. It was seen while J. N. Spitale was trying to confirm the orbit of another object, S/2004 S 3 that was seen 5 hours earlier just on the farther edge of the F ring.[1] The announcement was made on September 9, 2004.[3]

Even though astronomers tried to find it again, it has not been reliably seen since. Notably, an imaging sequence covering an entire orbital period at 4 km resolution taken on 15 November, 2004 failed to find the object. This suggests that it was a clump of material that had disappeared by that time.[4]

An interpretation where S3 and S4 are or were a single object on a F-ring crossing orbit is also possible.[3] Such an object might also be orbiting at a bit different inclination to the F ring, thereby not actually passing through the ring material even though it was being seen both radially inward and outward of it.

If a solid object after all, S/2004 S 4 would be 3−5 km in diameter based on brightness.

References[change | change source]

  1. 1.0 1.1 Martinez, C.; Ormrod, G.; and Finn, H.; Cassini-Huygens Press Releases: Cassini Discovers Ring and One, Possibly Two, Objects at Saturn September 9, 2004
  2. 2.0 2.1 PGJ Astronomie webpage (Gilbert Javaux) Note that the F ring is centered at ~140,180 km
  3. 3.0 3.1 IAUC 8401: S/2004 S 3, S/2004 S 4, and R/2004 S 1 2004 September 9 (discovery)
  4. 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. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006AJ....132..692S&db_key=AST&data_type=HTML&format=&high=444b66a47d06040.