Saturn's rings cast long shadows

By Phil Plait | October 3, 2011 3:51 pm

On Earth, one way to watch the march of the seasons is to look for lengthening shadows as winter approaches. As the Sun gets lower in the sky every day, objects like trees and buildings cast longer shadows.

On Saturn, there are no trees and buildings. There’s not even a surface! So what do you do?

Look to the rings:

[Click to encronosenate.]

This image, taken by the Cassini spacecraft on August 22, 2011, shows the shadows of Saturn’s magnificent ring system on the tops of the planet’s cloud layers. Right now, Saturn is tipping its north pole toward the Sun, so summer is on its way there. But that means winter’s approaching in the southern hemisphere, and shadows get longer.

Saturn’s rings aren’t solid, but composed of countless particles of ice, probably no bigger than a few meters across at most, and the vast majority much smaller. There’s also not just one big ring, but hundreds of thinner ones; from Earth, using small telescopes, they blur into what look like a handful of single rings. Big telescopes hint at the truth, but when you send an actual space probe there you see all those rings in their individual glory.

Here, Cassini was almost in the plane of the rings, so direct details are scarce. But with Sun shining down on them, the rings’ shadows make it very clear that when it comes to Saturn, there’s just no substitute for being there.

Image credit: NASA/JPL-Caltech/SSI

Related posts:

Titanic slice
A trillion and five moons
Saturn gets edgy
Cassini’s Pentaverate
Peeking past Rhea

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Cassini, rings, Saturn

Comments (20)

Links to this Post

  1. Saturn! « Bright Umbra | January 25, 2012
  1. TT

    You do know that those aren’t actual words you’re using in the [Click to …] line, right?


  2. ruidh

    Why, they are perfectly cromulent words.

  3. Wzrd1

    My wife wanted to know, what song is played when you put the needle in those grooves? 😉

  4. drbubbles

    So, those poor clouds on the polar edge of the widest shadow: how long before they see the sun again?

  5. David C.

    it is perfectly ligit that Phil change the “English” language, we never owned it in the first place; he is following in the footsteps of our greatest writer, Shakespeare, amongst (there is a good old English word gone out of fashion) hundreds of others; if not thousands around the world; go for it Phil 😉 google “the empire writes back” for an exhaustive treatment on the subject in the present day;

  6. At least he didn’t say “infundibulate.”

  7. I wonder how good our computer models of ring systems are. We obviously can’t keep track of every particle, so it has to be approached more like a fluid mechanics model, with bulk properties rather than point masses.

    Based on what I’ve seen of the Cassini photographs, I bet we can’t come close to the complexity of the real thing.

  8. Grand Lunar

    My new desktop image. :)

    Cassini never fails to deliver the shear awesome that is Saturn.

  9. Pete Jackson

    @4drbubbles: Any astronauts in the shadow of the rings would still see the sun for the most part. The A ring (outside the Cassini division) is relatively transparent, as is the inner part of the B ring. The darkest is the outer part of the B ring, inside of the Cassini division. Download the image and tinker with the brightness/contrast to see this.

    But for all those in the dark, think of the dazzling light impinging on the northern hemisphere, getting direct sunlight as well as all the light reflected from the rings! It must be positively balmy up there!

  10. Wzrd1

    @Rick #7, isn’t EVERYTHING fluid mechanics, at the end of the day? When one has gasses of different thermal and density characteristics, they behave like fluids. Plasmas behave like fluids, when in a mass. :)
    So, in essence, one need only calculate stream based and vortices, plus the shepherding moons. :)
    THAT said, I’m QUITE sure that high fidelity modelling would challenge our best clustered supercomputer.

    THAT all said, I’m trying to figure out WHY the rings shadows line up precisely like the UPC code for my can of split pea soup! 😉

  11. Messier Tidy Upper

    Wow. Thankyou Cassini and BA. Love this image. :-)

    @1. TT : “You do know that those aren’t actual words you’re using in the [Click to …] line, right? Right?”

    Not been here long then I take it TT? 😉

    Yes, the Bad Astronomer (BA) knows and so do the rest of it – its one of the quirky traditions of this blog and its been mentioned before many times and, like it or loathe it, he ain’t changing it.

  12. John

    I would think chaos theory would have application here…you’re not really trying to describe each individual ring particle’s position, motion, etc….more like averaging out enough samples to provide good predictions…maybe like what the quantum folks do to figure out the probability of where an electron is MOST LIKELY to be at a given time…


    How thick are the rings, Phil?

  14. Michael

    Beautiful post. Can’t get enough Saturn.

  15. jennyxyzzy

    Does anyone know if we have ever managed to get pictures from inside the… um is ‘orbit’ the right word?… of the rings? I don’t remember Cassini getting that close to Saturn, at least not yet (it’s planned for the end of the mission though isn’t it?), but maybe one of the Voyager spacecraft did?

  16. DennyMo

    Nice pic, but I really posted here to express my surprise that BA hasn’t said anything yet about this year’s Nobel Prize for Physics. :)

    I just finished reading “Death From The Skies” over the weekend, then heard the reports this morning on the Nobel, I can’t help wondering: what is the universe expanding into? I’m sure it’s a bad analogy, but if I blow up a balloon, it displaces the air as it expands. Is the universe displacing anything as it expands?

  17. flip

    Gorgeous image. This makes my day :)

  18. troy


    Can you really, and I mean, REALLY, tell us that Saturn’s rings cast long shadows, and then not actually tell us the length of the shadow cast? :) I mean, how are we truly supposed to be, er, astoundinated?

    Troy 😀

  19. Maria

    Mmm. Daily dose of space porn a go go!


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