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New ring discovered around Saturn
volcanopele
post Oct 7 2009, 10:27 PM
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not necessarily. As I pointed out before, for example, Janus and Epimetheus have a similar dust ring at their orbits made of micrometeorite ejecta and they have a prograde orbits around Saturn.

And adding to my list of "Moons with rings at their orbits", I should have also added Pan and Atlas.


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HughFromAlice
post Oct 9 2009, 01:12 PM
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News of the new Saturnian ring has travelled fast. Without being chauvinistic, I am glad to say I come from a forward looking scientifically literate country.......... our only quality national daily 'The Australian' has been quick to snaffle up this newsworthy item and give it a prominent place today. Who says we're behind the times down this way??????

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Round here it's out with the delta Vs and albedo calculations mad.gif and back to the good old trines and sesquiquadrates smile.gif ! Perhaps I'll swallow national pride and keep checking the UMSF pages laugh.gif !
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mchan
post Oct 9 2009, 01:20 PM
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Unenviable that you have astrologers finding a giant ring around Saturn. smile.gif
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djellison
post Oct 9 2009, 03:56 PM
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Would it be shorter to write a list of Saturnian moons that DON'T have associated dust rings? And would the same not be true of...er...anywhere with moons?
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brellis
post Oct 9 2009, 05:19 PM
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QUOTE (mchan @ Oct 9 2009, 06:20 AM) *
Unenviable that you have astrologers finding a giant ring around Saturn. smile.gif


Would they be Australogers? laugh.gif
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Gsnorgathon
post Oct 9 2009, 07:10 PM
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QUOTE (volcanopele @ Oct 7 2009, 02:27 PM) *
not necessarily. As I pointed out before, for example, Janus and Epimetheus have a similar dust ring at their orbits made of micrometeorite ejecta and they have a prograde orbits around Saturn.

And adding to my list of "Moons with rings at their orbits", I should have also added Pan and Atlas.

I wasn't very clear there... what I meant was, "might Phoebe's retrograde orbit have something to do with how huge the ring is, by contributing to higher-velocity impacts that would produce more ejecta and/or more widely-scattered ejecta, when compared with the rings formed by impacts on other moons?" But I'm having a hard time figuring out how that might work, anyway.

If Phoebe's a captured TNO, maybe it's just got a higher volatiles concentration, and the ring's a toroidal comet tail.
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Hungry4info
post Oct 10 2009, 03:22 AM
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Back during the Cassini flyby of Phoebe, I recall them saying that Phoebe was confirmed not to be a captured body. Is my memory faulty? (It was a long time ago.


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nprev
post Oct 10 2009, 04:52 AM
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I don't know how they could have confirmed that, frankly. The retrograde orbit alone is practically a smoking gun; AFAIK, all other known retrograde satellites are thought to be captured.


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Anne Verbiscer
post Oct 10 2009, 10:16 PM
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QUOTE (Julius @ Oct 7 2009, 12:18 AM) *
Could it be that Phoebe is a captured burnt out comet!?? blink.gif


That is precisely one of the scenarios we considered when we wrote our proposal to search for a ring with Spitzer. smile.gif
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nprev
post Oct 11 2009, 02:14 AM
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Interesting! Could you please describe some of the others, Anne?


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elakdawalla
post Oct 12 2009, 09:08 PM
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One idle thought led to another: I wondered if Cassini got whacked by any Phoebe ring particles as it passed through on its way in to SOI. Then I realized there's an instrument on Cassini designed to measure that, the CDA. Of course, that data's old enough that it's in the PDS. If I had time, I'd dig into it and see if I could understand or deal with the CDA data. I don't have time, though, so I just sent an email to the CDA team leader asking about it and hope I'll get a reply. But I thought I'd mention it here, just in case anybody else feels like attempting to dig into the PDS and see what CDA data looks like!

--Emily


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stevesliva
post Oct 14 2009, 04:12 AM
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QUOTE (stevesliva @ Oct 7 2009, 08:12 AM) *
Still an artist's impression. But the article said the discovery was made using Spitzer when it still had cryogen, and that the observations were of basically empty space.


Finally saw a "real" photo somewhere:
http://apod.nasa.gov/apod/ap091013.html

Original here:
http://www.spitzer.caltech.edu/Media/relea...c2009-19a.shtml
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Anne Verbiscer
post Nov 2 2009, 09:03 PM
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QUOTE (nprev @ Oct 10 2009, 10:14 PM) *
Interesting! Could you please describe some of the others, Anne?


Sorry to take so long to answer this!

Some of those 'other scenarios' explored the possibility that Phoebe at one time or another exhibited Chiron-like activity. The two objects have similar colors and perihelion distances; however, Phoebe appears to have more water on its surface (seen in near-infrared spectra) than Chiron does. Other possible sources of dust considered were collisional, from both major impacts and micrometeoritic erosion.
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Paolo
post Jan 24 2014, 06:27 AM
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I resurrect this years old thread to post this: the Cassini ISS instrument has apparently managed to image the Phoebe ring
First observations of the Phoebe ring in optical light


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