Cassini takes home video of Saturn's aurora

By Phil Plait | November 24, 2009 3:28 pm

Cassini keeps amazing me, even when I start to think I’m getting used to incredible images beamed back from Saturn.

But this is new: it took several images of Saturn’s aurora, and strung them together to make a video! Here’s a still frame:


The outline of Saturn is there, along with some latitude lines for reference (the bright thin wedge is the daylit side of the planet itself). You can see stars blurred in the background, with the aurora the orangey glow rising about the Saturnian cloud deck. This frame is cool, but for frak’s sake go watch the video! It’s mesmerizing. I’d put it here, but it’s 3 Mb and that would destroy the Hive Overmind servers.

The images put together to create the animation were taken over four days. Interestingly (well, to me anyway) these images were taken in visible light; we already know from Hubble observations that Saturn’s aurorae are bright in UV.

These northern lights on Saturn are formed in pretty much the same way they are on Earth: particles in the Sun’s solar wind get captured in the magnetic field of the planet, and are swept to the poles where they slam into molecules in the atmosphere, lighting it up (literally) like a neon sign. The details are far more complicated, of course, but that’s the basic picture. The images from Cassini don’t show color, which is too bad: the color of the glow can tell you what chemical elements are in the atmosphere, since different atoms emit at different wavelengths. Still, there is much to be learned about Saturn’s magnetic field from images like these.

And may I add: wow. Aurorae, from a billion kilometers away. Incredible!

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

Comments (11)

  1. Jason P.

    Hey Phil. Saw you on Nat Geo’s Hubble Show the other day. You da man!

  2. Messier TidyUpper

    Now there’s one stunning aurora borealis that you can’t see from Alaska or Iceland! ūüėČ

    Thanks to the Cassini team & the BA – marvellous! ūüėÄ

    Looks so much like flickering flames in a campfire that’s just burnt down to embers.

    The still shot from Hubble makes the background space and Saturn look very reddish – anyone know why?

    Also :

    “These observations, taken over four days, represent the first visible-light video of Saturn’s auroras.”

    Is that Saturn days or Earth days?

  3. Tim


    I will never get tired of these Cassini images.

  4. Looks as though saturn is on fire! As you say Phil mesmerizing!

  5. Wesley Struebing

    Absolutely awesome! While one can imagine something like aurorae on another world, to actually see it is beyong magnicent!

  6. Bryan

    Way cool movie. Not quite a correction, just a clarification. The particles in most aurorae do not necessarily get into the planet’s magnetosphere from the solar wind. Most of the particles come from the planet’s ionosphere. That’s at least the case for aurorae on planets with magnetopsheres (Earth and the Jovian planets). Aurorae on Venus and Mars are caused by the solar wind slamming directly into those planets’ atmospheres (and only occur on the day side). Cusp aurorae on magnetospherically endowed planets are also direct solar wind particles (they are also dayside aurorae). Don’t get me wrong, solar wind particles do leak into magnetospheres from open field lines, but that is a secondary effect. The solar wind does provide the energy that disturbs magnetospheres causing them to accelerate particles toward the planets. Anyway, great movie, and thanks for bringing it to my attention!

  7. B Lewis

    Incredible pictures. I watched the video on the site for a long time, just marveling at where it is and how these pictures came to be taken.

    Another incredible thing – “Death from the Skies” is in bookstores in Bangkok, which is where I finally got my copy. Just thought you’d like to know about your global profile.

  8. FC

    Off Topic: UFO Madness strikes again!

    Lovely Aurora… seriously 3 MB will blow the Hive Overmind? They need to get new servers, that’s a wimpy Hive Overmind.

  9. Just to clarify further–the particles in a planetary ionosphere are not energetic enough to excite aurora and the trapped particles in the Van Allen belts are not numerous enough. In fact, the terrestrial aurora would exhaust the radiation belts in hours. The auroral particles all come from the solar wind and are accelerated to the needed energy by electric fields in the magnetosphere that are in turn associated with the interaction of the planet with the solar wind.

  10. Dammit! That darn spacecraft just made me wet myself again!

    Freakin’ awesome! (The aurora, not the wetness.)


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