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MISSION ENDED

Kepler Space Telescope

The planet-counter that changed astronomy: from an Earth-trailing solar orbit Kepler stared at one patch of sky and confirmed over 2,700 exoplanets, proving planets outnumber stars in our galaxy. Retired in 2018 when its fuel ran out; the spacecraft still drifts silently around the Sun.

NASA·Earth-trailing orbit·Launched 7 March 2009·Mission ended
—days —h —m —s in space
Distance from Earth
267.09 M km
1.785375 AU
Distance from Sun
156.87 M km
1.04861 AU
Speed
102,860 km/h
28.572 km/s
Signal Delay
14.8 min
one way

Counting Planets

Kepler stared at one patch of sky in the constellations Cygnus and Lyra, watching about 150,000 stars for the tiny dips in brightness caused by planets passing in front of them. When it retired it had found more than 2,600 confirmed planets, and more have been confirmed from its data since. Its results showed that planets are common: there are more planets than stars in our galaxy.

K2 and Retirement

After a second reaction wheel failed in 2013, engineers used the gentle pressure of sunlight to steady the telescope and began the K2 mission, observing fields along the plane of the planets. Kepler ran out of fuel in 2018: NASA announced its retirement on 30 October and sent the final commands on 15 November 2018. The spacecraft still trails Earth around the Sun.

Mission Timeline

7 March 2009
Launch on a Delta II from Cape Canaveral
May 2009
Science observations begin
May 2013
Second reaction wheel fails, ending the original mission
2014
K2 mission begins, steadied by the pressure of sunlight
30 October 2018
NASA announces Kepler's retirement after its fuel runs out
15 November 2018
Final commands sent

Key Data

MissionKepler Space Telescope
AgencyNASA
StatusMission ended
TargetEarth-trailing orbit
Launch date7 March 2009
Mission ended15 November 2018

Questions people ask

Kepler follows Earth around the Sun in its own orbit, slowly falling further behind. It is about 267.1 million km from Earth. The spacecraft was switched off in November 2018, so it no longer sends any signal.
Thousands of planets around other stars: more than 2,600 confirmed by the time it retired, with more confirmed from its data since. Its biggest lesson was that planets are common, with more planets than stars in our galaxy.
It ran out of the fuel needed to point the telescope. NASA announced its retirement on 30 October 2018 and sent the final commands on 15 November 2018, after nine and a half years in space.

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