Searching for Earths
 The Kepler spacecraft is staring at a region of space between two of the brightest stars in the summer sky, Vega and Deneb. The orbiting telescope is monitoring 100,000 stars for evidence of Earth-like planets orbiting Sun-like stars. Such planets are considered the most likely home for Earth-like life. Kepler's search area, which is near the edge of the glowing band of the Milky Way, is denoted by the white boxes. [Carter Roberts/NASA]
In fact, that's where the Kepler spacecraft is looking right now. It was launched in March, and completed its checkouts in May.
Its goal is to find Earth-like planets in Earth-like orbits around Sun-like stars. Such planets are the most likely candidates for Earth-like life.
Kepler will stare non-stop at a hundred thousand stars in that region over the next three years. The stars are in the constellations Lyra and Cygnus, which are high overhead at nightfall. Kepler's starfield is centered between Vega and Deneb.
Kepler will watch for transits, which occur when a planet passes across the face of its star, blocking some of the star's light. Earth-like planets in Earth-like orbits will produce only a small drop, which lasts only a few hours. But the drop should repeat itself a few times during Kepler's mission, allowing scientists to measure the planet's size and orbit -- parameters that will tell us if it could have liquid water and a life-supporting atmosphere.
Scientists expect Kepler to find perhaps 50 Earth-like planets -- the prime targets for future searches for signs of life.
More about Kepler tomorrow.
Script by Damond Benningfield, Copyright 2009
For more about the Kepler Mission, visit NASA's website at http://kepler.nasa.gov.
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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