Kepler Spacecraft Blasts Off to Hunt Earth-Like Worlds
A Delta 2 rocket launches the Kepler spacecraft from Launch Pad 17-B at Cape Canaveral Air Force Station in Florida on March 6, 2009. The space telescope will hunt Earth-like planets around alien stars.
Credit: NASA TV

This story was updated at 12:10 a.m. EST on March 7.

NASA?s new planet-hunting Kepler telescope launched into space late Friday, lighting up the night sky above Florida as it began an ambitious mission to seek out Earth-like planets around alien stars.

Kepler blasted off atop a Delta 2 rocket from the Cape Canaveral Air Force Station in Florida at 10:49 p.m. EST (0349 March 7 GMT). The $600 million spacecraft will gaze at a single region of our Milky Way galaxy for at least three years in a planetary census that, scientists say, could fundamentally alter humanity?s view of its role in the universe.

?At the end of those three years, we?ll be able to answer, ?Are there other worlds out there or are we alone??? said William Borucki, Kepler?s principal investigator at NASA?s Ames Research Center in Moffett Field, Calif., before launch.

Kepler separated from its booster about an hour after liftoff and headed toward an Earth-trailing orbit that will circle the sun once every 371 days. The successful liftoff came on the heels of NASA?s Feb. 24 failure of a landmark climate-monitoring satellite, which crashed into the ocean just after launch.

A planet like ours ?out there?

Named after the 17th century German scientist Johannes Kepler, who discovered the laws of planetary motion, NASA?s Kepler spacecraft will use those laws to seek out Earth-like worlds around distant stars.

The spacecraft will point its unblinking eye at a patch of sky near the constellations Cygnus and Lyra, where it will scan some 100,000 stars for the telltale dip in brightness that signals a planet crossing in front of its parent star as seen from Earth. The tiny ?wink? in light that Kepler is designed to measure with its 95 million-pixel camera is comparable to a person trying to watch a flea cross a car?s headlight from miles away, NASA officials have said.

Astronomer Geoff Marcy, a Kepler co-investigator at the University of California at Berkeley, called Kepler a ?mission for the ages.?

?Kepler is the first telescope ever conceived by humanity that can actually detect planets like Earth,? Marcy said just before launch.

Since 1995, astronomers have discovered nearly 340 planets beyond our own Solar System, but the search has turned up mainly inhospitable worlds the size of Jupiter or larger that circle parent stars in orbits too extreme to sustain life as we know it.

NASA hopes to use Kepler to sift through those planetary behemoths for the smaller, rocky worlds - like our own Earth - that happen to orbit their parent stars in a region just right for liquid water to exist at the surface.

?What exists is an incredibly random, chaotic, you know, wild range of planets," said Debra Fischer, an astronomer at the San Francisco State University who is not directly involved with the Kepler mission, in a recent briefing. ?Kepler is really going to probe the habitable zones of planets."

The range of the so-called habitable zone, or Goldilocks zone, around a star varies depending on the star?s size, but is generally considered to be the region in which liquid water - an essential ingredient of life on Earth - can exist at the surface.  Too close to a star and a planet is too hot, while too far out will yield icy, frozen worlds, researchers said.

?What we want is a temperature that?s just right,? said Borucki. ?The so-called Goldilocks zone.?

More work ahead

With Kepler now in space, the work to outfit the telescope for its planet-hunting mission will begin in earnest.

Jim Fanson, NASA?s Kepler project manager at the Jet Propulsion Laboratory in Pasadena, Calif., said Thursday that flight controllers plan to spend the next two months performing a series of tests to make sure Kepler is healthy and ready to work. If all goes well, the protective dust cover shielding Kepler?s telescope eye will open about three weeks after liftoff.

Mission scientists hope to begin spotting larger Jupiter-like planets first, and then narrow the hunt down to Earth-like worlds as the mission wears on. While Kepler is designed to last about 3 1/2 years, it carries enough fuel to run for six years, they said.

But first, NASA has to get the spacecraft into its planet-hunting position.

?We have a lot of calibrations to do,? Fanson said.

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