Kepler spacecraft has discovered the first confirmed planetary system with more than one planet "transiting," or crossing in front of, a central star.
The findings, published in Thursday's issue of the journal Science, came from observing about 156,000 stars for seven months as part of a pioneering search for Earth-size planets outside our solar system.
Kepler's ultra-precise camera measures tiny decreases in a star's brightness caused by the orbiting of the planet as it crosses in front of its sun. The size of the planets can be determined by measuring these temporary dips.
Two planets in the newly discovered system, 2,000 light-years away, are the size of Saturn, and a third possible planet is a "super-Earth," 11/2 times the size of our planet. That planet is the size thought to be potentially habitable, but it orbits too close to its star to support life.
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