LOS ANGELES — NASA's planet-hunting telescope is broken.



The Kepler spacecraft lost the second of four wheels that control the telescope's orientation in space, NASA said Wednesday.



If engineers can't find a fix, the failure means Kepler won't be able to look for exoplanets — planets outside our solar system anymore.



"I wouldn't call Kepler down-and-out just yet," said NASA sciences chief John Grunsfeld.



Kepler was launched in 2009 in search of Earth-like planets. So far, it has confirmed 132 planets and spotted more than 2,700 potential ones.



While ground telescopes can hunt for exoplanets, Kepler is much more advanced.



Deputy project manager Charles Sobeck said there's a backlog of data that scientists still need to analyze even if Kepler's planet-hunting days may be numbered. For the past four years, Kepler has focused its telescope on a patch of the Milky Way hosting more than 150,000 stars, recording slight dips in brightness — a sign of a planet passing in front of the star.



Now "we can't point where we need to point. We can't gather data," Sobeck told The Associated Press.



Last month, astronomers announced Kepler's discovery of two distant worlds that are the best candidates for habitable planets.



The $600 million mission is managed by the NASA Ames Research Center in Northern California.