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Lasers II

May 18, 2010

Lots of bright stars twinkle across the sky tonight. As it gets dark, for example, there's Vega climbing into view in the northeast, and yellow-orange Arcturus high in the east-southeast. And the twins of Gemini line up to the right of the crescent Moon.

For a skywatcher, all that twinkling is a pretty sight. For a professional astronomer, though, it's a menace: It blurs the view through a telescope, turning what should be a crisp point of starlight into a fuzzy blob.

In recent years, though, astronomers have developed a new technique for bringing the night sky into sharper focus. It's called adaptive optics.

A telescope looks at a bright star that appears close to its target. Special mirrors in the telescope flex a tiny bit to compensate for the blurring effects of the atmosphere, bringing the guide star -- and everything close to it -- into sharp focus.

But there's not always a bright guide star around when you need one. So some telescopes create their own by firing a laser into the sky. The laser creates a glowing spot of light high in the atmosphere to serve as an artificial star. This spot of light suffers from the same blurring as a real star as it passes through the atmosphere. So when the adaptive optics system sharpens the view of the laser light, it also sharpens the view of the stars and galaxies around it -- getting rid of that pesky twinkling.

We'll have more about lasers in astronomy tomorrow.

Script by Damond Benningfield, Copyright 2010

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