NASA's revolutionary planet-hunting Kepler space telescope has run out of fuel and will be retired, the space agency announced Tuesday.
During its nine-year mission, Kepler found more than 2,600 planets orbiting stars outside the solar system _ including many with the potential for harboring life.
Thanks to the spacecraft, scientists have learned that the Milky Way galaxy has more planets than stars.
Kepler has overcome mechanical difficulties in the past. But without the fuel needed to conduct further science operations, NASA opted to end the mission.
The space telescope will remain in its current orbit, which is a safe distance from Earth, officials said.
