S/2004 S3 and S/2004 S4 |
S/2004 S3 and S/2004 S4 |
Nov 6 2006, 11:42 AM
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#1
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
On September 9th 2004, Nasa announced the possible discovery of two new Saturnian moons, spotted by Carl Murray, from pictures taken just prior to Cassini orbit insertion. Both appear to orbit within 1000 kilometres of the F-ring. In the intervening two years, as far as I'm aware, there have been no follow-up press releases on these possible objects. Does anybody have any subsequent information on these? Possibly (as stated in the release) they were just short-lived agglomerations of ring material, although diameters were quoted as being in the region of 4-5 km
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Nov 7 2006, 11:05 AM
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#2
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Junior Member Group: Members Posts: 76 Joined: 19-October 05 Member No.: 532 |
On September 9th 2004, Nasa announced the possible discovery of two new Saturnian moons, spotted by Carl Murray, from pictures taken just prior to Cassini orbit insertion. Both appear to orbit within 1000 kilometres of the F-ring. In the intervening two years, as far as I'm aware, there have been no follow-up press releases on these possible objects. Does anybody have any subsequent information on these? Possibly (as stated in the release) they were just short-lived agglomerations of ring material, although diameters were quoted as being in the region of 4-5 km There have been no new press releases about these or indeed any new F ring bodies since S/2004 S 6. The ISS team appears to have decided to stop anouncing satellite candidates in the F ring region presumably until they are reasonably sure that they are long lived objects and are reliably able to track them and predict their positions. |
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Nov 7 2006, 09:56 PM
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#3
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Thanks Pat - what you say makes sense. It's obviously a lot harder to track objects washed in the 'glare' of the rings than, say Methone, Pallene or Polydeuces (all a comparable size to that estimated for the F-ring candidates) which have all been pretty accurately orbit-determined now. Also I suppose that to be close enough means near periapsis, when demand is highest on the instruments and time is shortest.
There seems to be so much dynamism between the orbits of Prometheus and Pandora, I wouldn't be surprised (allowing for at least two more sizeable moonlets) if there's another example of Janus/Epimetheus orbit swapping going on in there, not to mention other orbital complications connected with the F-ring itself. I'd love to see (towards the end of an extended mission), some very close observations of this portion of the ring system over a period of a few weeks, aiming to resolve anything down to a hundred metres or so in diameter. |
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Apr 1 2008, 09:00 PM
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#4
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Some raw images of the rings taken just prior to periapse have been posted on the Cassini website. I'm aware of the pitfalls of seeing blobs in the raws, and interpreting them as moons, or clumps of material, but this one looks very moonlet-like to me.......
Cosmic ray hit? - this is a similar contrast to the surrounding scene Fortuitous appearance of background star in the gap? - this batch of images tends to have the background stars slightly smeared Dust speck on lens? - mmmm... I've cropped it from here and contrast enhanced slightly ADMIN CONVERTED JPG ATTACHED |
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Apr 17 2008, 05:27 PM
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#5
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
No dissent here, so I'm presuming I'm not imagining this - trouble is there was (I think) just the one frame, so it's almost impossible to confirm.
I'm still convinced that rubble is responsible for clearing out most of the observed gaps rather than gravitational resonances. |
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Apr 17 2008, 07:26 PM
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#6
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
I couldn't (can't) get your attached image to open. Maybe no dissent means others couldn't either. I think I see what you mean in the uncropped original you linked to but I'm not sure.
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Apr 17 2008, 09:01 PM
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#7
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Senior Member Group: Members Posts: 2998 Joined: 30-October 04 Member No.: 105 |
The image file has the incorrect extension. It's named snowball.jpeg when the filetype is a .psd .
--Bill -------------------- |
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Apr 18 2008, 08:03 PM
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#8
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Thanks admin for fixing the file extension - the cropped image shows this much more clearly.
It appears that the widest gap in the original image is the Huygens gap (with a small embedded ringlet), and the smaller gaps are exterior to this, at about 120,000km from Saturn's centre. This is obviously well inside the Roche limit - I wonder how far the tensile strength of ice would prevent tidal disruption? |
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Apr 18 2008, 08:17 PM
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#9
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Junior Member Group: Members Posts: 45 Joined: 30-November 05 Member No.: 592 |
Thanks admin for fixing the file extension - the cropped image shows this much more clearly. It appears that the widest gap in the original image is the Huygens gap (with a small embedded ringlet), and the smaller gaps are exterior to this, at about 120,000km from Saturn's centre. This is obviously well inside the Roche limit - I wonder how far the tensile strength of ice would prevent tidal disruption? before you all get way too excited......It's a star..... just about perfectly placed.... but that's what it is..... T |
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Apr 18 2008, 08:40 PM
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#10
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Quel dommage! - totally agree Tallbear that is near-perfect placement in the gap - must have caused a little ripple of excitement over at Ciclops though...
Oh well, back to the drawing board..... |
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