NASA’s four-year Kepler space telescope search for Earth-like planets circling distant stars has come to a close, space agency managers announced Thursday,
It was a disappointing conclusion to an effort by flight control teams to recover disabled reaction control wheels used to precisely aim the observatory that was launched in 2009.
Over the period, Kepler scored more than 3,500 exo-planet candidates. Of the total, 135 have been confirmed. However, it will take several years yet for astronomers to sift through the data to identify and confirm more.
“At the beginning of our mission, no one knew if Earth-size planets were abundant in the galaxy. If they were rare, we might be alone,” said William Borucki, Kepler science principal investigator at NASA’s Ames Research Center in Moffett Field, Calif. “Now at the completion of Kepler observations, the data holds the answer to the question that inspired the mission: Are Earths in the habitable zone of stars like our sun common or rare?”
Kepler was equipped to observe small dips in the light coming from distant stars in the Milky Way. Those dips corresponded to planets crossing in front of the stars.
In May, the telescope experienced the failure of a second reaction wheel. Three of the four spinning internal devices are required to aim the optics with enough precision to count planets. The first reaction wheel failed in July 2012.
On Aug. 8, Kepler managers concluded sustained precision pointing would not be possible after weeks of analysis and attempts to spin up the wheels.
On Aug. 2, NASA acknowledged a potential mission end by asking the science community to submit proposals for future Kepler observations using the two functioning reaction wheels and the satellite’s attitude control thrusters. The thruster fuel supply is limited.
“Kepler has made extraordinary discoveries in finding exo-planets including several super-Earths in the habitable zone,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate inWashington. “Knowing that Kepler has successfully collected all the data from its prime mission, I am confident that more amazing discoveries are on the horizon.”
In November, Kepler fulfilled its primary mission. Optimistic scientists won a four year extension.