NASA's space hunter, the Kepler Space Telescope, has wrapped up its prime mission and is moving into an extended four-year plan to continue searching for other worlds.
The space agency announced Wednesday that the Kepler has completed its initial three-and-a-half-year mission of searching the galaxy for Earth-like planets, meaning small, rocky planets orbiting sun-like stars.
Since it began its work on May 12, 2009, the telescope has searched more than 100,000 stars for signs of Earth-like planets in the habitable zone, an area that may have liquid water. The telescope has so far confirmed more than 100 of them.
NASA has decided to keep Kepler working, possibly as long as 2016, to continue the hunt for Earth-like planets.
"The Earth isn't unique, nor the center of the universe," said Geoff Marcy, professor of astronomy at the University of California, Berkeley, in a statement. "The diversity of other worlds is greater than depicted in all the science fiction novels and movies. Aristotle would be proud of us for answering some of the most profound philosophical questions about our place in the universe."
The telescope, which was launched in March 2009, is onboard a spacecraft that is also carrying several computers. Kepler is designed to measure the brightness of stars every half hour, allowing scientists to detect any dimming that would be caused by orbiting planets passing in front of them.
Scientists receive enough data from Kepler to determine not only the size of a planet but whether it has a solid surface and the potential to have water, which is crucial to the formation of life.
"The initial discoveries of the Kepler mission indicate that at least a third of the stars have planets and that the number of planets in our galaxy must number in the billions," said William Borucki, Kepler principal investigator, in a statement. "The planets of greatest interest are other Earths and these could already be in the data awaiting analysis. Kepler's most exciting results are yet to come."
