Feb 20, 2009

Kepler Mission to Hunt for Earth-like Planets

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February 20, 2009: Are there other worlds like ours? Are we alone?

NASA's Kepler spacecraft is about to begin an unprecedented journey that could answer these ancient questions.

Kepler is scheduled to blast into space from Cape Canaveral Air Force Station, Fla., aboard a Delta II rocket on March 5 at 10:48 p.m. EST. It is the first mission with the ability to find planets like Earth -- rocky planets that orbit sun-like stars in a warm zone where liquid water could be maintained on the surface.

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Above: An artist's concept of an Earth-like planet orbiting a distant star. Credit: Dana Berry/NASA. [video] [more]

"Kepler is a critical component in NASA's efforts to find and study planets where Earth-like conditions may be present," said Jon Morse, the Astrophysics Division director at NASA Headquarters in Washington.


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The mission will spend three and a half years surveying more than 100,000 sun-like stars in the Cygnus-Lyra region of our Milky Way galaxy. It is expected to find hundreds of planets the size of Earth and larger orbiting at various distances from their stars. If Earth-size planets are common in the habitable zone (where conditions favor liquid water), Kepler could find dozens of worlds like ours. On the other hand, if those planets are rare, Kepler might find none.

The Kepler telescope is specially designed to detect the periodic dimming of stars caused by transiting planets. Some star systems are oriented in such a way that their planets cross in front of their stars, as seen from our Earthly point of view. As the planets transit, they cause their stars' light to slightly dim, or wink: 1 MB video. The telescope can register changes in brightness of only 20 parts per million.

"If Kepler were to look down at a small town on Earth at night from space, it would be able to detect the dimming of a porch light as somebody passed in front," said James Fanson, Kepler project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

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To accomplish this feat, Kepler will use the largest camera ever launched into space, a 95-megapixel array of charged couple devices or "CCDs."

Right: Kepler's completed flight focal plane array with the 42 science CCDs and four fine guidance CCDs in the corners. [


By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles. This will allow astronomers to confirm the presence of planets. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm their presence. Ground-based telescopes and NASA's Hubble and Spitzer space telescopes will perform follow-up studies on the larger planets that they can see.

"Kepler is a critical cornerstone in understanding what types of planets are formed around other stars," said exoplanet hunter Debra Fischer of San Francisco State University. "The discoveries that emerge will be used immediately to study the atmospheres of large, gas exoplanets with Spitzer. And the statistics that are compiled will help us chart a course toward one day imaging a pale blue dot like our planet, orbiting another star in our galaxy."

For more information about the Kepler mission, visit:

Editor: Dr. Tony Phillips | Credit: Science@NASA

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Nomenclature: The science team chose to name the mission for Johannes Kepler (1571-1630) for his fundamental contributions to the fields of celestial mechanics and optics. It was Kepler who championed the Copernican idea of a heliocentric solar system, in which the planets all orbit the sun. Kepler discovered the laws of planetary motion—three basic mathematical expressions that describe the motions of planets.

Credits: Kepler is a NASA Discovery mission. Ames is the home organization of the science principal investigator, and is responsible for the ground system development, mission operations and science data analysis. JPL manages the Kepler mission development. Ball Aerospace & Technologies Corp. of Boulder, Colo., is responsible for developing the Kepler flight system and supporting mission operations. NASA's Marshall Space Flight Center, Huntsville, Ala., manages NASA's Discovery program.

NASA's Future: US Space Exploration Policy