NASA Podcasts

NASA Mission Update: KEPLER
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Are we alone? That’s a question likely asked by anyone who's ever stared in awe at the bright night sky.

Until recently, astronomers knew only of the planets in our Solar System. Then, in 19-95, came the discovery of the first planets orbiting stars other than our sun. Could they, like Earth, harbor life?

Padi Boyd: "We now know of over 300 exoplanets, planets around other stars. But the ones that have been found to date fall into categories that are not very similar to the Solar System."

With its sophisticated array of high-resolution cameras, the Kepler spacecraft is designed to stare at one region of our Milky Way galaxy and capture images of any transits it sees.

Padi Boyd: "Transit happens when a planet is passing in front of the face of its star. It's basically the same idea as when you see a solar eclipse. When that happens, that's the moon passing in front of the sun, and having a dramatic decrease on the brightness that we see of the sun."

How much starlight is blocked by a planet's transit, and how often that happens, can tell astronomers the planet's size and orbit, and whether it's in the habitable zone: not too close, nor too far away from its star.

Padi Boyd: "What we want to determine is how rare or common is a system like the Earth, with a planet like Earth, in a zone where you could have liquid water and, potentially, life."

Kepler will look continuously at well over 100-thousand stars for at least 3-1/2 years. The data it produces should be a significant step in learning whether "we've got company" in our galaxy, and tell astronomers where best to focus the search for neighbors.

Padi Boyd: "It's like when Galileo first turned his telescope to the heavens and everything changed: The way we thought of ourselves in the Universe changed. And the same thing happened when the Apollo astronauts took that picture of the Earth when they were around the moon. Everyone on Earth could see the Earth differently for that moment on. I think we'll have the same kind of revolution in the way we think of our Solar System and our existence when we know how special or how common we really are."

Narration: For more on the Kepler mission, visit

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