A little weekend Saturn awesomeness

By Phil Plait | May 28, 2010 12:01 pm

If you need a little more awesome in your weekend, then try this:


I know I’ve been posting quite a few Saturn images from Cassini, but I really like this one. It shows the big round moon Rhea, the lumpy small moon Janus, and a lovely view of the foreshortened rings. Both moons were on the far side of the rings, well over 1 million kilometers away, when Cassini took this shot. Rhea is over 1500 km (900 miles) in diameter, while Janus is only about 180 km (110 miles) across. For comparison, our own Moon’s diameter is almost 3500 km (2100 miles).

Just last year, the rings were edge-on to the Sun. In the months since, as Saturn slowly orbits our star, the Sun has begun shining down on the northern side of the rings. Cassini was just above the ring plane when it took this shot, catching the sunlight reflected off the rings. From this narrow angle, you can see the rings are divided into countless smaller ringlets, bright and dark sections carved into shape by the gravitational forces of the planet and its dozens of moons.

I love how the top of Rhea is playing hide-and-seek in the rings. And look how dark the rocky Janus is compared to the icy Rhea! Even at a glance you can see that Saturn’s environment is an amazingly rich and diverse place. Cassini’s observations will keep planetary astronomers busy for decades… and provide the rest of us with a glimpse of the beauty and awe just waiting to be uncovered.

Image credit: NASA/JPL/Space Science Institute

Related posts:

Don’t have gravity? Take your lumps.
The real Pandora, and two mooning brothers
Cassini eavesdrops on orbit-swapping moons
Wocka wocka wocka Mimas wocka wocka

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Cassini, Janus, Rhea, Saturn

Comments (18)

  1. Awesome, I love Cassini pics! How much farther away is Janus from Rhea in this pic?

  2. Wow! That truly is an awesome picture and just what I needed today. Thanks. :)

  3. Art

    I like it a lot! The rings almost look like I could skip across them.

  4. It never ceases to amaze me that we can fling robotic spacecraft to the outer solar system.

    Thank you science!

    (You too Phil)

  5. Brian

    Saturn (and specifically Cassini) was recently highlighted on The Big Picture blog. Of course just about everything on it has already been mentioned here …

  6. Janus may be dark, but at 0.64 g/cc, rocky it almost certainly ain’t.

  7. Kevin

    Saturn is always awesome!

  8. Kim

    Well, you know this is supposed to be Bad Astronomy and you are posting good stuff. Stop it. You think you can just post anything you want just because it is your blog and you’re the one writing it? I demand bad stuff or I’m going to go elsewhere and surf. Geez.

    Er um, so yea….

    It looks like Rhea is hiding under the rings from that angle.

  9. JBNoHo

    If anyone knows — how many degrees below the ring plane does Rhea actually orbit? I know it looks like it’s actually crashing into them, but that has to be an illusion of perspective.

  10. Blondin

    Just got this news:

    For immediate release: May 28, 2010


    Carolyn Porco, veteran planetary imaging scientist and leader of the
    imaging team on NASA’s Cassini mission at Saturn, has been awarded the
    2010 Carl Sagan Medal for Excellence in the Communication of Science to
    the Public by the Division of Planetary Sciences of the American
    Astronomical Society.

    Congratulations to Carolyn Porco. Well done.

  11. Messier Tidy Upper

    I know I’ve been posting quite a few Saturn images from Cassini,

    Please post all the Cassini shots you want, I can’t get enough of them! ūüėÄ

    (Not that you’d do otherwise anyhow! ūüėČ )

    Fanatastic and surely the most photogenic planet in our solar system. Magnificently gorgeous.

    Thankyou BA, love this blog, love that mission, what better combo could there be? :-)

    @10. Blondin : My congrats to Carolyn Porco too – she’d be my *other* favourite astronomer -well done. :-)

  12. Chris

    Please, please excuse my ignorance on this, but is Rhea actually in the Saturn rings? This is an illusion, right? Can anyone explain? Thanks!

  13. Pi-needles

    @ ^ Chris – yes it is, indeed, an optical illusion created by perspective. Rhea is orbiting well outside the rings just outside the E ring.

    See : http://en.wikipedia.org/wiki/File:Saturn%27s_Rings_PIA03550.jpg

    Curiously enough Rhea is the only moon thought to have a ring system of its own (not visible there) discovered a couple of years ago by Cassini & was once also labelled “Saturn V” – not to be confused with the rocket! ūüėČ

  14. bruce

    Isn’t it obvious that the lumpy “moon” is just a captive asteroid?

  15. mike burkhart

    This picture is awesome I think Cassini has been a good mission I was very intrested in the probe that landed on Titan .

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