The first stage of the Delta 2 launch vehicle that will carry the Kepler spacecraft into orbit waits for the installation of the final solid rocket boosters. nasa Visit the Photo Place

NASA mission searching for planets similar to Earth

The search is on for planets similar to Earth

Date published: 2/5/2009

WITHOUT a doubt, one of the most exciting discoveries in astronomy over the past few decades has been the fact that planets are orbiting stars beyond the solar system. Both astronomers and the public have been excited by the fact that planetary systems exist beyond our own.

As of Feb. 1, 2009, some 336 planets have been discovered orbiting distant stars, according to the PlanetQuest Web site planetquest.jpl.nasa.gov. These extrasolar planets, as they're called, are gas giants similar to the planet Jupiter, so the search is on for planets resembling the size and mass of Earth.

Extrasolar planets are very difficult to detect visually because they are small and hidden by the blinding glare of the stars they orbit. However, extrasolar planets have been discovered by using indirect methods such as observing a star's "wobble," caused by the gravitational tug exerted by an orbiting planet or by measuring the drop in a star's brightness as a planet passes in front of the star. The latter technique is called the transit method. From our earthly perspective, planetary transits happen in our solar system when Mercury and Venus pass in front of the sun on rare occasions.

Enter a new NASA mission named Kepler. Set for launch in March, it will be the first of several missions to find Earth-size planets. It consists of a spacecraft and an instrument called a photometer, which is a very sensitive telescope and light detector.

Kepler will concentrate on finding Earth-size planets orbiting distant stars using the transit method. The mission has an expected lifetime of four to possibly six years and will "stare" at 100,000 stars similar to our own sun located in the constellations Cygnus and Lyra.

Kepler's 95-megapixel detectors will allow the spacecraft to uncover possible extrasolar planets with unprecedented accuracy as it continuously gazes at the same part of the sky during its four-year mission. Kepler will concentrate on finding these planets in and around a star's habitable zone, the areas where planets may harbor water and atmospheres conducive to life.

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Date published: 2/5/2009