PASADENA, CALIFORNIA — The U.S. National Aeronautics and Space Administration (NASA) on Monday announced that its planet-hunting Kepler spacecraft has discovered its first planet which is located in its host star’s habitable zone.
NASA researchers also announced that Kepler, which was launched in March 2009 and was named after German astronomer Johannes Kepler who lived in the 17th century, has discovered more than 1,000 new planet candidates, nearly doubling its previously known count.
The planet Kepler-22b is the first confirmed planet found by Kepler which is located in the habitable zone, the region around a star where liquid water (and as a result, life) could exist on a planet’s surface. The planet is about 2.4 times the radius of Earth but is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun.
“This is a major milestone on the road to finding Earth’s twin,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. “Kepler’s results continue to demonstrate the importance of NASA’s science missions, which aim to answer some of the biggest questions about our place in the universe.”
Kepler-22b is located 600 light-years away and its orbit of 290 days around a sun-like star resembles that of Earth. Although the planet’s host star is slightly smaller and cooler than our sun, it belongs to the same class which is called a G-type.
Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets that cross in front, or “transit,” the stars. Kepler requires at least three transits to verify a signal as a planet.
“Fortune smiled upon us with the detection of this planet,” said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field in California, who led the team that discovered Kepler-22b. “The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season.”
Although Kepler has now identified a total of 2,326 planet candidates, only 10 of them are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.
Photo : Kepler-22b System Diagram – Image credit: NASA/Ames/JPL-Caltech