Southern lights greet ISS and Atlantis

By Phil Plait | July 18, 2011 10:30 am

On July 16, an astronaut on the International Space Station captured this eerie and cool picture of Atlantis and the ISS with the aurora australis in the background:

[Click to embiggen.]

You can see Atlantis on the right and one of the station’s solar panels on the left. In the middle is the Orbiter’s robot arm hanging down (as much as "down" makes any sense in space). That light near the top of the arm is not a star but an actual light, to help illuminate shadowed areas being worked on.

The aurora australis, or southern lights, are the counterpart to the aurora borealis (northern lights). The actual phenomenon is quite complicated, but in essence subatomic particles from the Sun are captured by the Earth’s magnetic field. They’re channeled down to the magnetic poles, which are very near the Earth’s physical poles. The particles slam into the atmosphere, stripping electrons off of air molecules. When the electrons recombine with the molecules, they give off light exciting the electrons in atoms high in the air, and when the electrons give up that energy the atoms glow. The color depends on the atom or molecule involved; oxygen emits strongly in the green, while nitrogen is preferentially red. In reality most substances emit at several different colors, but the strengths change; oxygen emits in the red as well but much more weakly than green. When you see red in an aurora, it’s usually mostly nitrogen you’re seeing.

That thin brownish arc is real too! That’s a layer of aerosol haze, particles suspended high in the atmosphere. When we look up from the ground we see right through it, but seen from nearly edge-on it becomes visible. You can spot it in a lot of photos of the Earth’s limb taken at night from space.

I’ll admit, when I first saw this picture it momentarily threw me. How could the clouds be so bright (like it’s daytime) and yet the aurora be visible? Then I remembered that the Moon was just past full on July 16, when this picture was taken. Even though this is a night scene, the Moon was bright enough to light up the clouds. The exposure time was several seconds (you can see the stars are slightly trailed as the Orbiter moves around the Earth), plenty of time for the Moon to illuminate the clouds. It also lit up the cowling over the Orbiter’s engines as well.

Today, Monday, July 17, the astronauts from Atlantis moved from the ISS back to the Orbiter and closed the hatches. Tonight at 02:28 Eastern (US) time (06:28 GMT), Atlantis is scheduled to undock from the station, and on July 21st it will return to Earth for the final time, marking the end of the Shuttle era for NASA.

Related posts:

A puzzling planet picture from the ISS
The green fire of the southern lights
Flying through the aurora at 28,000 kph
OK, because I like y’all: bonus aurora time lapse video

MORE ABOUT: Atlantis, aurora, ISS

Comments (16)

Links to this Post

  1. The Dawn of a New Era | | July 28, 2011
  1. Andy Beaton

    OMFSM! Look at that giant Space Lobster claw on the left!

  2. Bigfoot

    Is that a robotic arm sticking out of your cargo bay, or are you just …

    Beautiful picture — made better by the romance of the knowledge that the clouds are moonlit. Now I hope the shuttle does not have a … er, uh, … *difficult* time folding that arm back up inside when it has to return home for the last time. Who could blame it?

  3. Molly

    I sent this photo to my sister in gmail chat, and she said “Dang it! You always send me the neatest things!”

  4. David

    Sure, it’s beautiful. But it makes me wonder how much of that radiation is negatively affecting the health of the astronauts.

  5. magisterial

    It’s a streetlight.

  6. Trebuchet

    Re “Down”: Seems to me that in LEO, the direction of the center of the Earth is a perfectly valid definition. The ISS is, after all, not just floating in space, but constantly falling around the planet, moved by the ever-present gravity. It’s only its tangential velocity that keeps it up.

  7. Trebuchet makes a great point, it’s not like a skydiver during free fall says “there’s no such thing as down because I’m weightless!”. I think it’s pretty clear when skydiving which way down is!

    For anyone that was wondering, The ISS-Shuttle were travelling roughly Northeast at the time this photo was taken. While the Shuttle is docked the complex is facing “backwards” as compared to it’s typical orientation in order to protect the Orbiter’s heat shield tiles. Thus, this photo was taken looking back the way they had come – or along the negative velocity vector, if you prefer.

    You can also tell that this photo was taken roughly at orbital midnight because the solar arrays are perpendicular to the Orbiter. The photovoltaic side of the arrays point at the sun even at night – it’s just that the Earth is in the way!

    Hope that helps!
    Ad astra,
    – Ben H.
    ISS Flight Controller
    Houston, Texas

  8. @ ^ Ben H : Thanks for that informative comment – and please keep up the good work. :-)

    Superb photo, eerie and magnificent. :-)

    @4. David Says:

    Sure, it’s beautiful. But it makes me wonder how much of that radiation is negatively affecting the health of the astronauts.

    I’m guessing not too badly at all. There have been a great many astronauts and cosmonauts launched into space over the years, a fair number of them have stayed many months even I think well over a year in some cases on the various space stations – Skylab, the Salyuts, Mir and the International Space Station. They seem to be okay and not too badly affected radiation~wise far as I’ve heard. I’m sure they’ve done studies and calculations on this and decided its not that much of a problem.

  9. RwFlynn

    I have to wonder if we have effected any visible change, over the last hundred or so years, in the layer of aerosols we’re seeing here. Are there any useful pictures out there for that sort of thing?

  10. Zucchi

    People who fly into space get to see things that we groundhogs will never see. And that’s just LEO. Someday humans will stand on Rhea and look up at Saturn. (Unless civilization collapses first.)

  11. Mike

    “embiggen”????? Really?
    I would think that an editor, astronomer, lecturer, and author would use something other than a word invented by “The Simpsons”. Seriously, other than a single reference to an obscure book from 1884 ( William John Thomas et alios, Notes and Queries: A Medium of Intercommunication for Literary Men, General Readers, Etc, p135 ), there is no reference to this word in the Mirriam-Webster, Oxford or Cambridge dictionaries. The only other reference is to a 1996 episode of “The Simpsons”.

  12. Messier Tidy Upper

    Incidentally, my local newspaper ‘The Advertiser’ has just published this image (page 32, 20th July 2011) in a brief article on the final Space Shuttle flight ever – & it now adorns my pinboard. :-)

  13. (Paul) Terry Hunt

    Mike @ 11:

    Inventing and adopting new words for new(ish) concepts is a routine feature of living languages. The concept of moderately enlarging an in-blog picture for easier viewing is evidently sufficiently new for a new term to be felt desirable, and “embiggen” has been widely adopted, not least by the professional linguistics blog Language Log (see for example the mouseover instruction at If it’s good enough for them . . . .

    Nor do I see anything wrong with taking up a word (re)invented by cartoonists, as opposed to some other type of artist or writer. If this worries you, how do you feel about “thagomizer” – the array of spikes on the tail of a stegasaurus – being adopted by paleontologists following its first appearance in a Gary Larson cartoon? (See

  14. #11 Mike:
    Was the operation painful? Your sense of humour bypass, I mean!
    I assume you’re a newcomer here, as variations on your comment have been appearing for the last couple of years. As well as using “embiggen”, Phil frequently invents his own words to mean the same thing, appropriate to the subject of the images. It’s all a running joke between Phil and his readers.
    What you’re basically saying is that an editor, astronomer, lecturer and author isn’t allowed to have a sense of humour!

  15. #11 Mike
    I don’t see anything wrong with “embiggen.” It’s a perfectly cromulent word to use. ūüėČ

    Phil’s a funny guy, and part of humor is twisting language. His use of a pop culture reference is well within the bounds of artistic license and satirical fair-use. All that aside, the editor in me would have a field day with your comment. Glass houses and all that.

    I didn’t know that about the thagomizer! You just made my day.


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