Faint Ring Thread, Saturn's D, E and G rings |
Faint Ring Thread, Saturn's D, E and G rings |
Jul 17 2005, 08:23 PM
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#1
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
There are two new "Raw Images" up that give a good view of Saturn's D Ring. As of today (July 17th) they are on the first page of the Raw Images section. The better of the two is image number W00009347.
The very narrow inner ringlet is called D68 and it is the innermost well defined ringlet of the entire ring system -- it's only about 7250 kilometres above the cloud tops, about half-way from the planet to the inner edge of the C Ring. If you search the "Saturn-D Ring" section of Raw Images, there is a nice narrow angle view (N00035241) which I am pretty sure is a close-up of D68. D68 is an oddball, it really is sort of "in the middle of nowhere". The brighter ringlet in the upper right is called D73. About a thousand kilometres inward from D73, there is a noticeable "dark zone". In the Voyager images, there was a third bright narrow ringlet inside this zone, D72, which seems to be gone now, strangely enough. The relevant Voyager images are Voyager 1 image 34946.50, and Voyager 2 image 44007.53. If the diffuse ringlet at the inner edge of the "dark zone" is what is left of D72, it looks to have migrated a bit closer to Saturn in addition to spreading out a lot. (By the way, I'm not making up these ringlet designations on the fly -- they are given in a paper by Mark Showalter that was published in Icarus in 1996, which is pretty much the only major paper on the D Ring.) To give some idea of scale, the three bands of material in the far upper right corner are part of the innermost ringlet of the C Ring (this can also be seen on some images of the rings taken on May 3rd of this year). Since it is so faint and doesn't appear in many images, the D Ring rarely attracts much attention. But it's kind of neat to look at if you haven't seen it before, particularly because of D68, which is sort of the "anti-F ring" in a way. |
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Aug 24 2008, 01:50 PM
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#61
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
if it's a moonlet why haven't we seen it already? My guess would be phase angle. Both the Aug 15th and 22nd observations were done at low phase angles where a solid object would back-scatter light. If the majority of G ring imagery in the past was high phase (optimized for actual particles which forward-scatter light) it would be hard to pick up a small crescent bathed in scattered light of the particle clump. This, on the other hand, looks like ideal viewing conditions for a solid object. My money's on a small moonlet. -------------------- |
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Aug 24 2008, 02:22 PM
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#62
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
The follow-up observations lend weight to the idea that it's a moonlet, perhaps suspected from earlier imaging campaigns of that region of the D-ring.
What of the fact that it's well inside the Roche limit though?? |
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Aug 24 2008, 02:25 PM
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#63
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
We're talking about the G ring.
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Aug 24 2008, 02:32 PM
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#64
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Oops, getting my rings mixed up
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Aug 24 2008, 02:48 PM
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#65
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
-------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Sep 4 2008, 12:16 PM
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#66
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
No G-Ring images on the August 29th (unless I missed something). Maybe they will take some tomorrow on the 5th. Would be nice to get an image targeting/tracking the G-Ring object/clump.
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Sep 4 2008, 02:04 PM
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#67
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Junior Member Group: Members Posts: 55 Joined: 8-November 06 From: Indiana, USA Member No.: 1337 |
Aren't we still in Solar Conjunction?
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Sep 6 2008, 03:00 PM
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#68
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
Yes we are in conjunction, but comming out.
There is a very nice Cassini News report on rings and ring arcs associated with small Saturn moons. On the G-Ring they state: "This is probably the same mechanism responsible for producing the arc in the G ring," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, N.Y. Hedman and his Cassini imaging team colleagues previously determined that the G-ring arc is maintained by a gravitational resonance with Mimas, much like the new, small moon arcs. "Indeed, the Anthe arc may be similar to the debris we see in the G-ring arc, where the largest particles are clearly visible. One might even speculate that if Anthe were shattered, its debris might form a structure much like the G ring," Hedman said. I still wonder if the image of the G-Ring object was smeared because it is an extended clump, or if the image was not targeted to track the rotation of the ring. -Floyd -------------------- |
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Sep 6 2008, 03:16 PM
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#69
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
Nice image of Anthe arc from the news writeup.
"The moon is moving downward and to the right in this perspective. In this image, most of the visible material in the arc lies ahead of Anthe (2 kilometers, or 1 mile across) in its orbit. However, over time the moon drifts slowly back and forth with respect to the arc. The arc extends over about 20 degrees in longitude (about 5.5 percent of Anthe's orbit) and appears to be associated with a gravitational resonance caused by the moon Mimas. Micrometeoroid impacts on Anthe are the likely source of the arc material. The orbit of Anthe lies between the larger moons Mimas and Enceladus." -------------------- |
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Sep 10 2008, 11:28 PM
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#70
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
According to Ciclops Looking Ahead for Rev 84, on September 13th, "Cassini will then observe an arc of material in the G ring that was recently observed to have a denser clump of material within it."
We should know more soon. -------------------- |
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Sep 15 2008, 07:33 PM
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#71
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
I can't see any clumps of interest in the G-Ring images from September 13 & 14. The 13th's images are almost edge on and the 14th's have so much camera flair that I can't even find the G-ring. I'm sure the Cassini team can subtract out the flair, so there is probably good information somewhere in the images.
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Oct 29 2008, 02:01 AM
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#72
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
Some nice images of Ering which sure look a lot like the Gring. "Taken on October 27, 2008 and received on Earth October 28, 2008. The camera was pointing toward SATURN-ERING at approximately 1,199,543 kilometers away". I've seen pictures of the Ering with Enceladus embedded. This set of three has a nice moving clump--which made me think it the the Gring and clump. Looks like the Ering has both Enceladus and a clump. Open all three images in tabs and flip through to see the climp and stars move.
Image1 Image2 Image3 -------------------- |
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Oct 29 2008, 03:44 AM
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#73
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
No, that's definitely the G ring. Not sure why it is labeled as the E ring though.
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Dec 10 2008, 09:46 AM
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#74
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Nice bump with shadow:
http://saturn.jpl.nasa.gov/multimedia/imag...6/N00125063.jpg |
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Dec 10 2008, 03:11 PM
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#75
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Solar System Cartographer Group: Members Posts: 10173 Joined: 5-April 05 From: Canada Member No.: 227 |
A bit late - but that E-ring image is presumably labelled E-ring because it's centered on the E-ring. The label tells you what the camera is pointed at, regardless of what else might be in the image.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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