The Great … Black Spots?

Contributed by
Aug 1, 2006
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The other day, I wrote about Jupiter's drive-by spots. A new image of the close encounter between the über-hurricanes was just released, taken by the ginormous Keck 10-meter telescope (picture a mirror about as big as one side of a tennis court).

The image above shows the wide field view of Jupiter on the left. The colors look almost normal, but they're not: they are in the near infrared, at about twice the reddest wavelength the human eye can detect. You can clearly see the Great Red Spot, and Red Jr (which I prefer to call Oval BA, its official name) right next to each other, though they look white in the infrared.

The (frankly creepy) close-up is way out in the IR, at 5 microns, where warmish things glow. By warm, I mean about 300 Centigrade, so a fair bit hotter than boiling water, if I did my math correctly. Note that the spots are black! That means they are cold compared to 300 C. According to the Keck folks, the clouds in the spots block the infrared light from the hotter stuff deeper down in the atmosphere, so they appear black. Still, heat leaks out around the edges, so you can see them faintly outlined by hot gas.

The weird polychromatic inkblot thing at the top is the moon Io (roughly the same size as our Moon). It looks funny because it moved a little bit between exposures, so it appears as a line of colored dots. What's very interesting to me is that the blue image (at 1.65 microns) is significantly bigger than the other two. I emailed the folks at Keck about it, and got a reply right away. It turns out that this filter lets through light from methane. Jupiter is faint when viewed through that filter, so to make the color picture look right they had to increase the brightness of the blue image. That made Io look bigger. It goes to show you-- seeing is not necessarily believing, and just looking at an image and trying to understand what you're seeing is a lot harder than you think.

Not really a tip o' the dew shield, since it's her job to send out media stuff, but more of a shout-out to my friend Laura K. Kinoshita at Keck, listed on their page as a media contact. Since I knew her until recently as Laura Kraft, I assume her marriage went off... with a hitch. Hahahaha! Get it? She got hitched. Oh, I kill me. Anyway, she eventually answered my email even though she's on maternity leave. So Hi Laura, and congrats!