Kepler's Broken Wheels Leave Earth Without a Planet-Spotter

NASA's Kepler spacecraft on the launch pad at Cape Canaveral, weeks before its takeoff in 2009 Photograph by Jack Pfaller/NASA

Earth’s most skilled planet-hunter, the Kepler Space Telescope, needs a new job. Over the past four years, it has spotted 135 planets and identified more than 3,500 other possible ones, but that work is now over, hobbled by malfunctioning hardware.

The 2,300-pound telescope operates with four “reaction wheels,” momentum-canceling flywheels designed to keep it perfectly stable during lengthy observations of distant stars, when minute blips of light can reveal a potential planet orbiting its star. One of the Kepler’s wheels failed in July 2012, followed by a second in May. NASA said on Thursday that it’s abandoned efforts to repair them.

Those malfunctions have left Kepler unable to perform its primary mission, leaving NASA to contemplate whether there are other projects the telescope can conduct with two reaction wheels. Earlier this month, the agency issued a call for proposals (PDF) on work it could perform. Possibilities include research on comets and asteroids.

Why does the end of a space telescope’s planet-scouting days matter? If we discover life on another planet, Kepler will be hailed as one of the true pioneers in that endeavor. “At the beginning of our mission, no one knew if earth-size planets were abundant in the galaxy,” William Borucki, a Kepler project member at NASA’s Ames Research Center, said in a news release. “If they were rare, we might be alone.”

Kepler’s planet-spotting is among the first astronomy to show that the pattern of our solar system, in which earth and other planets circle a sun, appears common elsewhere in space. The goal now for astronomers is to locate large planets occupying a so-called habitable zone—meaning that, like earth, they’re at a suitable distance from their stars to support life. Scientists confirmed the first such planet, called Kepler-22b, in late 2011.

Kepler’s formal mission ended in November, but the observatory was supposed to keep collecting data through 2016. The telescope, launched in March 2009, is named after the 17th century German astronomer Johannes Kepler, who articulated the laws of planetary motion around the sun.

Later this year, the European Space Agency plans to launch its Gaia space telescope, a five-year mission to create a 3D catalogue of 1 billion stars, about 1 percent of the 100 billion stars in our galaxy. That map’s precision is expected to discover numerous new planets, furthering the work of Kepler.

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