Ring near edge on illumination, Ring particles are casting shadows Options

[elakdawalla]

That's cool, Astro0, thanks for that. Although the edge of the B ring is the most "mountainous" place in your pan, when I wander around it I see some other noisier-looking spots -- I wonder if those are places where there's some topography to the rings.

--Emily

(P.S. Thanks, Stu. Having all of y'all's commentaries to start from makes things easy.)

[fredk]

These are ridiculously spectacular images. Sorry if someone has already mentioned this, but there appears to be a correlation between the length of the ring shadow and the brightness of clumps in this ring, which certainly makes sense.

We can also obtain information about the extent of structures perpendicular to the rings elsewhere, by the absence of visible shadows. Where we can't see ring shadows, any shadow present must have a length of order 1 pixel or less. Using the figures quoted above (7 km/pixel scale, 1.9 degree sun angle), that means any structures elsewhere must be less than roughly 200 metres in height. Of course this limit will improve as the sun angle decreases...

[belleraphon1]

When CASSINI launched I never expected THIS!

A leapin and hoppin on a moom shadow ......... (thanks for that Emily... have not listened to the Cat in years)...
SO... just cannot stop the leapin and hoppin in my minds eye now.. a rainbow bridge of cascading light and shadows, along a bumpy grainy plain that sails off to the limits of our current vision.....

I am blown away.... how grand!!!!

Craig

[ngunn]

APOD today. The 'preliminary hypothesis' link goes to Emily's blog, and 'jagged shadows' comes straight here.

EDIT: Oh no . . . the 'cast' link goes to Cat Stevens . . .

[ngunn]

Here's another calculation. I wanted to know roughly how fast the relative motions are between these jostling clumps.

Taking the peak amplitude of the displacement from the ring plane as 2 km and the radius and orbital velocity of the outer B ring as 117600 km and 17970 m/s respectively I get:

Maximum perpendicular velocity (whilst crossing the ring plane) = 2 x 17970 / 117600 = 0.3 m/s.

So, even for particles or clumps rising and falling exactly in antiphase, collision velocities would be less than 1 m/s.

Makes you realise just how gentle most of the rest of the rings must be.

[Stu]

A few years ago the BBC produced a series called "Space Odyssey" (re-christened "Voyage To The Planets" for overseas markets) and while it wasn't 10000% accurate scientifically, it did feature some truly breathtaking images and visuals, such as an astronaut flying through Saturn's rings...

http://www.youtube.com/watch?v=tTrh26hBUlQ

The Saturn's rings EVA begins at 4.53 if you want to skip to that part.

The series got quite a lot of stick for being cheesy and melodramatic, but I've watched it again and again, just because it inspires such wonder when I do. Well worth checking out the DVD, or trawling YouTube for the rest of it.

[ngunn]

Hey, that is indeed a beautiful animation of the ring particles, thanks Stu. (Best watched with the sound off though.)

[Fran Ontanaya]

The great wall of Saturn...

At the right side of the third frame there's a round spot, as if a free moonlet was casting a shadow on the wall of dust. To the left of it, a pillar of dust and its shadow seems to appear.

[volcanopele]

APOD today.

Uh oh....

[chemman]

The great wall of Saturn...

At the right side of the third frame there's a round spot, as if a free moonlet was casting a shadow on the wall of dust. To the left of it, a pillar of dust and its shadow seems to appear.

Just noticed that myself and was going to post, but I see you beat me to it. Good observation. I think the background shadow you are attributing to the "pillar" might actually be the shadow of the moonlet instead. The shadows should appear at an angle to the corresponding foreground objects since this section of the ring is not directly parallel to the sun. Just my thoughts.

[ugordan]

Just noticed that myself and was going to post, but I see you beat me to it.

I don't see it. All I see is the resize filter smoothing out unresolvable pixel values. A dark pixel inside a brighter area will tend to look circular, especially with the bicubic resample filter.

[chemman]

I don't see it. All I see is the resize filter smoothing out unresolvable pixel values. A dark pixel inside a brighter area will tend to look circular, especially with the bicubic resample filter.

I haven't done my own processing yet, but it appears it might be in the other images and moving. I don't know the time separation between the images so it's difficult to tell if the apparent object is moving at a constant rate. What caught my initial attention was the appearance of what appears to be a corresponding shadow in the last frame at an angle consistent with the shadows of the other ring objects. I agree though, with the resolution we have it could just be an illusion or a artifact of the image processing.

OK, after further review I concur it's a processing artifact.

[jasedm]

All I see is the resize filter smoothing out unresolvable pixel values.

I was going to say that..

[Floyd]

I started this thread because I was really blown away by the images of the outer edge of the B ring. I correctly guessed that many UMSFers would be fascinated as well. However, I didn't (and don't) believe finding the images scooped the Cassini team in any way. They had predicted that protuberances in the rings would cast informative shadows. See the following Cyclops news release of March 23, 2009.LINK

Excerpts from the Cyclops news release:
[During equinox, Saturn's moons can shadow the rings], especially those whose orbits are inclined with respect to the equator, begin to intersect the planet's rings. When this occurs, the equinox period has essentially begun, and any vertical protuberances within the rings, including small embedded moons and narrow vertical warps in the rings, will also cast shadows on the rings. At exactly the moment of equinox, the shadows of the rings on the planet will be confined to a thin line around Saturn's equator and the rings themselves will go dark, being illuminated only on their edge. The next equinox on Saturn, when the sun will pass from south to north, is Aug. 11, 2009. … Because of these unique illumination circumstances, Cassini imaging scientists have been eager to observe the planet and its rings around the time of equinox, and Cassini's first extended mission, which began on July 1, 2008, and extends to Sept. 30, 2010, was intended to gather observations during this time. Hence, its name: Cassini Equinox Misson. … Cassini imaging scientists first predicted when and where the moons' shadows would fall on the rings and then planned special imaging sequences to target those locations. … More than just pretty pictures, these observations and others to come could provide valuable information regarding the presence of any deviations across the rings from a perfectly flat wafer-like disk. Working outward from the planet, the main rings are named C, B, and A. Saturn's ring system is wide, spanning hundreds of thousands of miles or kilometers. But the main rings are perhaps only 10 meters (30 feet) thick, and they lie inside the F ring which is vertically thicker than the A, B and C rings, making the determination of interior vertical deviations difficult when imaging the rings edge-on.

Assuming Bjorn Jonsson's calculations are correct (post 17), the outer edge of the B ring is warped approximately 3 km which is large compared to 10 meter ring thickness mention above. We at UMSF are certainly having a lively discussion and doing great things with the images, but I am quite sure that the Cassini team recognized the significance of these images as soon as they hit the ground. It may take the scientists a while to comment, but I'm sure they are all over this and planning additional sequences to get just the right images for publication.

[Astro0]

Perfectly said Floyd.

For the majority of contributors, UMSF'ers are armchair explorers only and for us it's just fun to ponder the possibilities and guess at what we are seeing. The Cassini team like all the other mission scientists and engineers are the experts, and they tell us the facts when they know them. We respect and appreciate the fact that they even share this data with the public at all. For the moment, we are just the wide-eyed audience on the outside looking at the magic they produce.