StarDate: March 2, 2009

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The roster of known planets outside our own solar system is about to get a whole lot bigger. A spacecraft called Kepler will spend the next three and a half years staring at a hundred thousand stars for evidence of planets -- especially planets like Earth.

BOSS: It will look to see if any of those stars happen to start periodically blinking themselves -- that is, dimming the amount of light they give off as seen from Earth. And if you can rule out all other sources of why a star should periodically dim by a small amount, then K will be able to make the claim that it's actually seeing planets in orbit around those stars.

That's Alan Boss, an astronomer who's working on the Kepler mission. He explains that the stars will grow fainter as their planets pass in front of them, blocking a tiny bit of their light.

BOSS: In the case of Earth-like planets, we are looking for something very hard to do, actually, because what you're going to be looking for is a very tiny dimming of the star, by maybe a part in 10,000, which will only last for an hour or two, a few hours at most, and we want to look at it and see it happen one time, then one year later, which is the Earth's orbital period, see it happen again, wait another year later, see it happen a third time, then we really think we've got something happening. so it's going to be a mission which is fraught with long periods of boredom with moments of extreme excitement...

If scientists are correct, Kepler will see evidence of hundreds of planets in other star systems -- including a few Earth-like worlds that are in just the right spot for life. More about that tomorrow.

Script by Damond Benningfield, Copyright 2009

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