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Kepler Gave Us the Best Evidence Yet That We Are Not Alone

NASA's planet-finding telescope is now on life support: Here's why it mattered.

by Jason Koebler
May 16 2013, 3:25pm

NASA went out of its way to make sure Wednesday's status update on Kepler, the agency's planet-finding space telescope, wasn't seen as a funeral. But if I'm ever in the hospital and people start talking about me like this, kill me.

If Kepler's not dead, it's certainly a vegetable.

Scientists controlling the spacecraft went to check on it Tuesday and found that one of its four reaction wheels, which let the telescope point at things it wants to see, wasn't responding. NASA went through the same thing last year, and hasn't been able to get that reactor wheel working. It needs at least three to function, and John Grunsfeld, who runs NASA's science mission directorate, said the telescope "is not in a place where I or any other astronaut can go up and rescue it."

The other Kepler scientists aren't ready to take it off life support yet, but it seems like they're ready for the inevitable. In what seemed like a series of eulogies given by people whose careers are in danger of getting sequestered away (NASA is on the verge of canceling its Kepler Science Conference in November), Paul Hertz, astrophysics director at NASA HQ and Bill Borucki, Kepler's principal investigator, reminisced on the good times.

"I'm delighted that the mission gave us four years of excellent data," Borucki said. "On the other hand, I would have been even happier if it had continued for another four years. That would have been the frosting on the cake, but we do have an excellent cake."

He's got a point there: Kepler never gave us the ridiculously gorgeous images we get from Hubble, but it gave us the best evidence--at least if you use your imagination--that we're probably not alone in this big thing we call the universe. 

Artist rendering of Kepler-47, the first solar system discovered with multiple planets orbiting a pair of stars. Photo via.

Kepler's mission in life was to stare out into the night sky, monitoring approximately 150,000 star sequences constantly and looking for faint flickers. Those flickers, astronomers suggested, could be caused by planets passing in front of their stars during orbit. Take a look at the size and spot of the shadow the planets cast, and you've got a reasonable estimate of a planet's size and distance from its star. Find one that's in the "habitable zone"--far enough away so that you wouldn't be melted to death if you're a humanoid alien, but close enough to still have liquid water--then send our greetings to its (maybe) inhabitants when we develop a warp drive.

Kepler scientists were hoping to find a couple "Earth-like" planets--instead, they've found 132 confirmed planets, another 2,740 planet "candidates," and they still have at least two years worth of data to comb through. Scientists have also found "binary systems," a new, pretty common class of solar system with planets that orbit two stars.

Just last month, a Notre Dame astronomer found two planets in a five-planet solar system that are "the closest thing ever found to Earth." They are just 1.41 and 1.61 times the size of Earth, and are roughly as far away from their star as we are.

"Before we flew Kepler, we didn't know that Earth-sized planets in habitable zones were common throughout our galaxy," Hertz said. "We didn't know that virtually every star has planets."

If Kepler goes out like this, and it sounds like it probably will, it didn't have the best of timing. 

Just last week, the House Subcommittee on Space held a hearing called "Exoplanet Discoveries: Have We Found Other Earths?" in which Republicans Lamar Smith and Steven Palazzo heaped praised on Kepler and its discoveries. 

Palazzo said the discovery of planets in the habitable zone "has broad implications not only for the scientific community, but for all mankind." Smith said the "discovery of life outside our solar system would alter our priorities for space exploration and how we view our place in the universe."

Kind of a bummer, then, that Kepler is being put into a fuel-saving "Point Rest State," where it won't be able to do much besides sit there and hope someone can rescue it. The team is still exploring whether Kepler can be used to do some other sort of astronomy, but without being able to point it at a specific spot, that seems unlikely. 

There's still the off chance that NASA gets Kepler's wheel started again. But the wheels are known to have a limited lifetime, and Kepler's mission was only supposed to be three and a half years. When scientists saw the quality of information they were getting back, the mission was extended until at least 2016. Recent indications suggested that the wheel would be breaking soon, and it seems like NASA was trying to squeeze every last bit of data out of it.

"We do not know how much longer it will be able to maintain the very precise pointing required for its exoplanet mission, but we do know that Kepler's legacy is secure," Grunsfeld testified at the Congressional hearing last week. Consider these staggering numbers:

Thanks to the Kepler mission, we now know that when you go outside and look up at the night sky, virtually every star you see has at least one planet around it. Based on the latest Kepler results, scientists estimate that at least 17 percent of all the stars out there have rocky planets orbiting them. Of even greater interest, the results suggest that 15 percent of M stars–the smallest, coolest class of stars, but also by far the most common type of star in the galaxy–have rocky planets in the habitable zone. This number tells us that the nearest potentially habitable planet could be only 15 light-years away.Moreover, if that trend holds for other classes of stars, it would mean that there are approximately 50 billion potentially habitable rocky planets spread throughout our own galaxy.

NASA has the Transiting Exoplanet Survey Satellite launching in 2017 and the James Webb Space Telescope launching in 2018--both missions will attempt to find planets located closer to Earth. Until then, scientists will parse through two more years worth of data, looking for a planet that looks like ours.

"People are saddened; it's definitely not good news for a mission that's been performing so well," Hertz said. "But after we've answered the questions [a mission] was built to answer, as Kepler has done, we move on to additional questions."

If old crippled Kepler's ready to kick the bucket, it's had a hell of a life.