NASA’s Kepler mission was designed to find Earth-size planets orbiting in the habitable zones of other stars.
The Kepler space telescope launched on March 7, 2009, and monitored the brightness of more than 150,000 stars. It searched for tiny, repeated dips in starlight caused when a planet passes in front of its star, an observation method called the transit technique.
Kepler’s original mission ended after the failure of two reaction wheels in 2013, but the spacecraft continued in the K2 mission using pressure from sunlight to control its pointing. Together, Kepler and K2 identified thousands of confirmed exoplanets and candidates, transforming knowledge of planets beyond the Solar System.
Kepler is often confused with Hubble, Spitzer, or Chandra. Those observatories made major discoveries in other areas, but Kepler’s primary purpose was a statistical survey of planets around other stars.