Ringed Mirage

Ringed Mirage

Ringed Mirage

Bad Astronomy
The entire universe in blog form
Aug. 10 2005 12:34 AM

Ringed Mirage

Sigh. I'm getting my dander up talking about all this ID nonsense, so how about some real science for a day or two, OK? I'm gonna talk about air here for a minute. Just as a breather (harhar!).

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

Air bends light. But you knew this: you've seen pictures of mirages, and you've seen the weird shimmering reflection over hot asphalt in the summer. You've read my web page about why stars twinkle.

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As you look closer to the horizon, the air gets thicker; you're looking through more air (that's because the Earth is curved, and the atmosphere curves with it-- draw yourself a picture!). Right near the horizon, the amount of air you look through changes the most, and so light gets bent the most there. As the Sun sets, its light gets bent upwards, squashing the bottom of the image of the Sun up into the top.

Earth is not all that special; other planets have atmospheres. Take Saturn, for example. It has a very thick atmosphere. If you were floating in space, and looked at something just beyond the planet's surface, its light would get bent as well, distorting your view of the shape of the object.

Well, we have something floating near Saturn: the Cassini probe. And it has cameras on board, and it can see this bending of light. The picture below shows it! The camera takes pictures in the infrared, and where methane strongly affects the light. The rings seen in the image go behind Saturn (the planet itself is the bright vertical band on the right), and just as they go behind the top of the atmosphere, the light gets bent in the same way sunlight does at sunset here.

This image is very cool. But it's also useful: scientist can measure the amount that light bends, and get the vertical distribution of methane in Saturn's atmosphere.

Science is beauty. Don't ever doubt it.