S/2004 S 4
| Discovery | |
|---|---|
| Discovered by | Cassini Imaging Science Team.[1] |
| Discovered on | June 21, 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 provisional designation of an unconfirmed object seen orbiting Saturn within the inner strand of the F ring on June 21, 2004. It was spotted while J. N. Spitale was trying to confirm the orbit of another provisional object, S/2004 S 3 that was seen 5 hours earlier just exterior to the F ring.[1] The announcement was made on September 9, 2004.[3]
Despite later attempts to recover it, it has not been reliably sighted since. Notably, an imaging sequence covering an entire orbital period at 4 km resolution taken on November 15, 2004 failed to recover the object. This suggests that it was a temporary 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 slightly different inclination to the F ring, thereby not actually passing through the ring material despite 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
- ^ a b Martinez, C.; Ormrod, G.; and Finn, H.; Cassini-Huygens Press Releases: Cassini Discovers Ring and One, Possibly Two, Objects at Saturn September 9, 2004
- ^ a b PGJ Astronomie webpage (Gilbert Javaux) Note that the F ring is centered at ~140,180 km
- ^ a b IAUC 8401: S/2004 S 3, S/2004 S 4, and R/2004 S 1 September 9, 2004 (discovery)
- ^ 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. doi:10.1086/505206.
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