APOD: Saturns Rings from the Dark Side (2012 Dec 31)

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APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby APOD Robot » Mon Dec 31, 2012 5:06 am

Image Saturns Rings from the Dark Side

Explanation: What do Saturn's rings look like from the dark side? From Earth, we usually see Saturn's rings from the same side of the ring plane that the Sun illuminates them -- one might call this the bright side. Geometrically, in the above picture taken in August by the robot Cassini spacecraft now orbiting Saturn, the Sun is behind the camera but on the other side of the ring plane. Such a vantage point gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the rings have similarities to a photographic negative of a front view. For example, the dark band in the middle is actually the normally bright B-ring. The ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles. At the top left of the frame is Saturn's moon Tethys, which although harder to find, contains much more mass than the entire ring system.

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby owlice » Mon Dec 31, 2012 5:10 am

Stunning image!! Great text and links, too!

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Beyond » Mon Dec 31, 2012 5:15 am

Well... it's alright... but i think i was spoiled by the last(?) saturn picture that was shown, from the back-side, with the greenish hue.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby owlice » Mon Dec 31, 2012 5:39 am

Just "alright"??

:: passes out cold ::
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby bystander » Mon Dec 31, 2012 5:47 am

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby starstruck » Mon Dec 31, 2012 6:45 am

Time and again I try to imagine a more aesthetically stunning alien world and I just can't do it! Saturn rules! And APOD ends the year on a high!

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Mactavish » Mon Dec 31, 2012 6:55 am

owlice wrote:Just "alright"??

:: passes out cold ::


“Alright”, indeed. Very, VERY alright!! Another brilliant encore by Cassini!

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby bay area john » Mon Dec 31, 2012 7:15 am

So... it seems the rings are directly over the equator of Saturn... or are they? If so, is that to be expected of ring systems, part of the tidal forces that keep them suspended? Actual Moons don't seem to be so constrained to a single specific plane, do they?

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Chris Peterson » Mon Dec 31, 2012 7:43 am

bay area john wrote:So... it seems the rings are directly over the equator of Saturn... or are they? If so, is that to be expected of ring systems, part of the tidal forces that keep them suspended? Actual Moons don't seem to be so constrained to a single specific plane, do they?

Moons can orbit at any inclination (although most tend to be fairly close to the equatorial plane). Rings are only stable over the equator, however, because all planets (and especially gas giants) are somewhat oblate. That creates forces that eventually pull orbiting bodies into equatorial alignment, but nonequatorial rings would fall apart quickly.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby alter-ego » Mon Dec 31, 2012 7:45 am

bay area john wrote:So... it seems the rings are directly over the equator of Saturn... or are they? If so, is that to be expected of ring systems, part of the tidal forces that keep them suspended? Actual Moons don't seem to be so constrained to a single specific plane, do they?


Cassini FAQ wrote:Why do Saturn's rings all lie in the same plane? Why are planetary rings always found in their equatorial planes and not sometimes crossing their poles?

Saturn, its rings, and most of its moons all probably formed from a spinning disk of gas and dust within the original solar nebula. As it collapsed toward its center, it would have formed a central sphere (which became Saturn), leaving a disk of material orbiting its equator. That material probably coalesced into many or most of Saturn's moons. The ring particles may be material that was left over from this process, or they may be the remnants of a moon that was shattered by collision or by tidal forces (see Roche limit). In either case, the ring particles would have kept the angular momentum of the original disk, and continued orbiting Saturn in its equatorial plane.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby RedFishBlueFish » Mon Dec 31, 2012 11:20 am

The black & white brings out what appears to at least one crater on Saturn.

This seems odd, as I did not think that the surface of the planet was visible.

As the dawn of this New Year's Eve brings METAR 311053Z 10006KT 2SM -DZ BR OVC003 10/10 A3006 it looks as though I might have time to find out a bit more, as won't be going outside.

Happy New Year All!

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby orin stepanek » Mon Dec 31, 2012 12:46 pm

I'm sorry; but I think this is a view of the day side of Saturn! Look where the terminator is! :shock:
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Ray-Optics » Mon Dec 31, 2012 1:01 pm

Yes, we see sunlight on Saturn's face. Imagine you're Saturn and you're wearing a broad-brimmed hat. You pull the hat down against the sunlight. Now, are you looking at the dark side of the brim? Yes.

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Ray-Optics » Mon Dec 31, 2012 1:05 pm

RedFishBlueFish: I wondered about that too. It can't be a crater. It almost looks like an asteroid impact only a few hours old. I'm surprised it wasn't mentioned by the editor.

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby orin stepanek » Mon Dec 31, 2012 1:43 pm

Ray-Optics wrote:Yes, we see sunlight on Saturn's face. Imagine you're Saturn and you're wearing a broad-brimmed hat. You pull the hat down against the sunlight. Now, are you looking at the dark side of the brim? Yes.


Thanks! Good explanation! 8-)
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby neufer » Mon Dec 31, 2012 3:00 pm

Ray-Optics wrote:
RedFishBlueFish: I wondered about that too. It can't be a crater. It almost looks like an asteroid impact only a few hours old. I'm surprised it wasn't mentioned by the editor.

viewtopic.php?t=30256#p188364
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Boomer12k » Mon Dec 31, 2012 4:27 pm

RedFishBlueFish wrote:The black & white brings out what appears to at least one crater on Saturn.

This seems odd, as I did not think that the surface of the planet was visible.

As the dawn of this New Year's Eve brings METAR 311053Z 10006KT 2SM -DZ BR OVC003 10/10 A3006 it looks as though I might have time to find out a bit more, as won't be going outside.

Happy New Year All!


It is either a cloud structure, if you look closely up above it, you also see some WHITER spots, or it could be a camera artifact. I am thinking an asteroid, would have a blackish ring or mark around it, like Jupiter did.

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby saturno2 » Mon Dec 31, 2012 4:31 pm

Image of Saturn for the end 2012.
I think this picture is very interesting. Indeed.
Saturn, Saturn
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby ta152h0 » Tue Jan 01, 2013 4:53 am

the Dec 22 APOD looks closely the same
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby RedFishBlueFish » Tue Jan 01, 2013 12:45 pm

Boomer12k wrote:
RedFishBlueFish wrote:The black & white brings out what appears to at least one crater on Saturn.
This seems odd, as I did not think that the surface of the planet was visible.

It is either a cloud structure, if you look closely up above it, you also see some WHITER spots, or it could be a camera artifact. I am thinking an asteroid, would have a blackish ring or mark around it, like Jupiter did.

Did spend a little time yesterday looking on the web, but have not actually found an answer.

It does not seem to be a lens artifact, a perfectly circular storm "eye" with no evidence of inflow is not likely, recent impact seems possible - but it would have been a spectacular event and surely would have been noted. If do not get called in today, will look about a bit more.

Again - and officially now - Happy New Year!

And I remain puzzled.

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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby bystander » Tue Jan 01, 2013 4:58 pm

Click to play embedded YouTube video.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Beyond » Tue Jan 01, 2013 5:58 pm

I think that hint may be a little too subtle. :mrgreen:
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby bystander » Tue Jan 01, 2013 6:17 pm

Beyond wrote:I think that hint may be a little too subtle. :mrgreen:

Obviously, neufer's hint was too direct.

viewtopic.php?f=29&t=30256 wrote:
Even Saturn's rings appear to dwarf Tethys (660 miles, or 1,062 kilometers across), which is in the upper left of the image, although scientists believe the moon to be many times more massive than the entire ring system combined.

I think it's amazing such a tiny moon could be more massive than Saturn's spectacular rings.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby owlice » Tue Jan 01, 2013 7:02 pm

Moon shadows on Saturn typically appear inky black, just as the shadows of the rings do. I don't know what the spot is -- maybe a camera or processing artifact -- but it appears far too light to me to be a moon shadow.
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Re: APOD: Saturns Rings from the Dark Side (2012 Dec 31)

Postby Chris Peterson » Tue Jan 01, 2013 7:16 pm

owlice wrote:Moon shadows on Saturn typically appear inky black, just as the shadows of the rings do. I don't know what the spot is -- maybe a camera or processing artifact -- but it appears far too light to me to be a moon shadow.

7205_17346_1p.jpg
I assume we're talking about the circular structure below the rings, towards the lower pole? It's just a storm system. The same system shows up in other images made around the same time, such as the one here taken a couple of weeks later.
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