Cassini's slant on the rings

By Phil Plait | July 2, 2010 9:40 am

Check out this latest image from Cassini at Saturn!


[Click to embiggen.]

Oh, wow! This was taken when the spacecraft was almost in the plane of the rings, which are incredibly thin. You can see several different rings, including the broad A ring in the middle and the thin F ring on the outside. There are also two moons: Janus (the larger one, above) and Prometheus (smaller, below). Janus is about 180 km (110 miles) across, which isn’t terribly big, but Prometheus is even smaller: 120 km (75 miles).

cassini_epimetheus_pandoraThis picture made me smile not only because it is carved out of raw coolness, but also because it’s the complement of an earlier image from Cassini (to the right). The earlier shot is of the moon Epimetheus, which shares an orbit with Janus, and Pandora, which shares an orbit with Prometheus! So the two images go together like a pair of gloves, each showing one of a pair of orbit-sharing moons.

Also, in the big image, take a look at the thin F ring: follow it from the far side to the near side. Just as you pass the bottom left and start moving to the upper right, do you see two spots where it appears thicker, like it’s lumpy? Well, it is lumpy! Pandora and Prometheus are the ring’s shepherd moons, using their gravity to keep the ring particles tightly in place. But when they pass any given point in the rings, their gravity leaves a wake behind, almost like a boat’s wake. That deforms the ring a bit, and you can see that in this image as a thickening in the ring. The animation I’ve inserted here actually shows that as it happens.

Amazing, what can be seen in a single image from Saturn. Especially if you have other images to back it up.

I like this new image a lot. Hmmm, have I found my new desktop picture? Why yes, yes I have.

Tip o’ the CICLOPS to Carolyn Porco.

Related posts:

A little weekend Saturn awesomeness
Cassini eavesdrops on orbit-swapping moons
Dr. Tongue’s 3D House of Prometheus
The bringer of fire hiding in the rings

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Cassini, Janus, Prometheus

Comments (10)

  1. Messier Tidy Upper

    Beautiful photo. Thankyou Cassini team & Bad Astronomer. ūüėÄ

  2. Messier Tidy Upper

    Sorry – inadvertant duplicate comment deleted by me. Mea culpa.
    (Going to bed to catch up on much needed sleep now.)

  3. jcm

    The Lord of the Rings and its minions. Way cool.

  4. nobody

    Cool photo!!!

  5. Damon

    Pandora? I thought I kept hearing the same planet over and over.


    Phil Plait posts an interesting astronomy article on Cassini at Saturn, and it gets only four five comments (not counting mine); however, whenever he posts a personal opinion on some non-astronomical subject matter, which is what ‘blogs’ are about, we get the usual cry coming from certain individuals: “I thought this was an astronomy blog!!!”

    Ingrates! :roll:

  7. Messier Tidy Upper

    @ ^ IVAN3MAN_AT_LARGE : Hey *I’m* not! I even made a point of saying ‘thanks’ – not for the first or, no doubt last time either. Some people remember their manners & I try (not always successfully I’ll confess) to be polite! ūüėČ

    Still it is interesting to see this will be comment 7 here & there’s 15 comments on the “Big bruiser stars form like their wimpy little siblings” & 24 on the “Did Hayabusa return empty-handed?” astronomy posts as I type compared with a whopping 179 as of right now on the “Climategate’s death rattle” thread.

    Yet folks say they only want astronomy posts here? :roll:
    Go figure.

  8. The Cassini ring photos you’ve been showing here have been blowing my fragile little mind. Thanks and keep ’em coming.

  9. MarcoDL

    Phil, you’re not the only one who has found his new desktop image :-)

    kudos to the Cassini team and to the little probe itself!


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