Kepler (spacecraft)

Kepler is a space observatory launched by NASA to discover Earth-size planets orbiting other stars. The spacecraft, named after the Renaissance astronomer Johannes Kepler, was launched on March 7, 2009, into an Earth-trailing heliocentric orbit.

Designed to survey a portion of our region of the Milky Way to discover Earth-size exoplanets in or near habitable zones and estimate how many of the billions of stars in the Milky Way have such planets, Kepler's sole science instrument is a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view. This data is transmitted to Earth, then analyzed to detect periodic dimming caused by exoplanets that cross in front of their host star.