Kepler was launched in 2009. Its mission was to determine the fraction of stars in the galaxy that harbor Earth-like planets by carrying out a survey of about 150,000 stars in the constellations of Cygnus and Lyra, looking for the dips in starlight caused by planets passing, or transiting, in front of their suns. So far, it has confirmed 132 planets and spotted more than 2,700 potential ones.
Since Earth transits only once a year, two more years would have given astronomers a chance to see more transits of the planets they are looking for. Without the extra time, the data will be noisy, astronomers say, and so the answer will be a little more uncertain than it might have been.
Last month, astronomers announced Kepler’s discovery of two distant worlds that are the best candidates for habitable planets. The other planets found by Kepler haven’t fit all the criteria that would make them right for life of any kind — from microbes to man.
While ground telescopes can hunt for planets outside our solar system, Kepler is much more advanced.
In January engineers noticed that one of the reaction wheels that keep the spacecraft pointed was experiencing too much friction. They shut the spacecraft down for a couple of weeks to give it a rest, in the hopes the wheel’s lubricant would spread out and solve the problem. But when they turned it back on, the friction was still there. Until now, the problem had not interfered with observations, which are scheduled to go on until at least 2016.
Sobeck said there’s a backlog of data that scientists still need to analyze, even if Kepler’s planet-hunting days may be numbered.