S/2004 S 4
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| 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 provisional designation of an unconfirmed object seen orbiting Saturn within the inner strand of the F ring on 21 June 2004. It was spotted while J. 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 15 November 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 S4 would be 3−5 km in diameter based on brightness.
[edit] References
- ^ a b Cassini-Huygens press release about discoveries around the F ring in 2004
- ^ a b PGJ Astronomie webpage (Gilbert Javaux). Note that the F ring is centered at ~140,180 km
- ^ a b IAUC 8401
- ^ J.N. Spitale et al (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal 132: 692.
| Moons of Saturn | |
|---|---|
|
Generally listed in increasing distance from Saturn
|
|
| Ring shepherds | Pan · Daphnis · Atlas · Prometheus · S/2004 S 6 · S/2004 S 4 · S/2004 S 3 · Pandora |
| Co-orbitals | Epimetheus · Janus |
| Inner large and Trojan | Mimas · Methone · Pallene · Enceladus · Tethys (trojans Telesto, Calypso) · Dione (trojans Helene, Polydeuces) |
| Outer large | Rhea · Titan · Hyperion · Iapetus |
| Inuit group | Kiviuq · Ijiraq · Paaliaq · S/2004 S 11 · Siarnaq |
| Norse group | Phoebe · Skathi · S/2006 S 8 · S/2004 S 13 · S/2006 S 4 · S/2004 S 19 · Mundilfari · S/2006 S 6 · S/2006 S 1 · S/2004 S 17 · Narvi · S/2004 S 15 · S/2004 S 10 · Suttungr · S/2004 S 12 · S/2004 S 18 · S/2004 S 9 · S/2004 S 14 · S/2004 S 7 · Thrymr · S/2006 S 3 · S/2006 S 7 · S/2006 S 2 · S/2004 S 16 · Ymir · S/2006 S 5 · S/2004 S 8 |
| Gallic group | Albiorix · Erriapo · Tarvos |
