Kepler mission scheduled to lift off today

ZUI this post from the Los Angeles Times:

The first spacecraft dedicated to finding potentially habitable planets beyond our solar system is poised to blast off from Cape Canaveral tonight on a three-year mission to probe 150,000 stars in the most sweeping hunt for Earthlike objects ever undertaken by NASA.

By the end of the Kepler mission, scientists will probably know whether planets like ours -- where liquid water can exist on the surface to nurture life -- are common in the universe, or so rare that we are virtually alone in the cosmic sea.

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The $590-million Kepler mission, scheduled to lift off at 7:49 p.m. Pacific time, consists of the widest-field telescope ever flown by NASA. The nearly 15-foot-long instrument has a 55-inch-wide mirror that can simultaneously scrutinize thousands of stars in its search for extrasolar planets, or exoplanets. It will accomplish this by looking for periodic dimming -- or winking -- of a star's light caused by planets crossing in front of it, which scientists refer to as a transit.

Many of the 340 or so known exoplanets, principally discovered by a team in Europe and another at UC Berkeley headed by well-known planet hunter Geoff Marcy, have been found using the same method.

But most of those planets are gas giants, like Jupiter, that orbit very close to their parent stars. Those planets would be far too hot to sustain life, even if they had a rocky surface.

No potentially habitable planet has been found outside our solar system.

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The Kepler spacecraft -- named after 17th century German astronomer Johannes Kepler, who discovered the laws of planetary motion -- will be able to scan a region of the northern sky between the constellations Cygnus and Lyra that contains about 4.5 million stars. Of the total, according to mission scientist Natalie Batalha of San Jose State University, 150,000 stars have been selected for intense study.

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Kepler will launch on a three-stage Delta II rocket and eventually drift about 45 million miles away so it won't have to contend with the reflected light of the moon and Earth.

Most of the stars in its survey are relatively close, from tens of light-years to 3,000 light-years away.