For the last four years, the Kepler mission has been searching for distant relatives of the Earth. Today, NASA announced that their planet-hunting space telescope is no longer able to keep up that search.
Two of four reaction wheels on the Kepler probe have stopped spinning. Without these crucial stabilizers keeping the telescope pointed toward the right patch of space, Kepler will have to be shut down for the foreseeable future.
"Kepler has completely exceeded expectations, so I can't say I'm disappointed," said San Diego State University professor William Welsh, one of the many astronomers on the Kepler team. "But I'm saddened we won't get to continue."
Kepler was launched four years ago in order to find and study planets beyond our own solar system. On all counts, the mission has been an incredible success. Astronomers now know that planets are actually abundant in the Milky Way galaxy.
They also now know about dozens "Goldilocks" planets, which orbit their stars within the habitable zone. These planets have the right sizes and temperatures needed to potentially sustain life. Welsh and his colleague at SDSU, Jerome Orosz, recently helped track down the two most Earth-like planets yet discovered by Kepler.
Reflecting on this major crossroads for the Kepler mission, Orosz said, "It's one of the best things that's happened in my scientific career." Compared to other NASA missions in recent years, he would rank the success of Kepler "very near the top."
Signs of trouble came yesterday when NASA put Kepler into safe mode, prompting speculation that the telescope was experiencing serious technical difficulties. In a press conference Wednesday afternoon, NASA officials confirmed that they aren't able to send astronomers to Kepler in order to fix the wheels.
"The telescope will start to drift, and there's no way to prevent that," said Welsh. "It's like trying to balance a tripod on two legs instead of three. It just doesn't work."
NASA officials were cautiously optimistic about the future of the telescope, assuring that they'll be investigating ways to fix the wheels remotely. They're not out of options yet, Welsh admitted, but he said, "Those are probably long-shots."
Kepler's principal investigator William Borucki clarified that even if the telescope's data-gathering mission is brought to an end, that does not mean Kepler astronomers suddenly have no work left to do. "We still have large quantities of data already downloaded and ready for analysis," he said.
Borucki expects Kepler researchers to confirm the existence of even more Earth-like planets as they sift through all this data. "I'm very optimistic that the data we have will allow us to do that," he said.
