In March 2009, the Kepler spacecraft was launched. Named after astronomer Johannes Kepler, Kepler was designed as a three-year mission to explore “the structure and diversity of planetary systems including Earth-size planets in the habitable zone surrounding other stars, the region where liquid water could pool on the surface and support life.”‘
The mission was successful, finding five “hot Jupiter” planets, a rocky planet, a planet with two stars, several planets in the habitable zones of their stars and an Earth-size planet in the habitable zone of its star. 4,034 candidate planets were found in all, with 2,335 of them confirmed.
In addition, Kepler observed other phenomena; such as supernovae, an eight-planet solar system, the “final stages of a solar system,” and more.
After nine years searching the skies, the Kepler spacecraft has reached the end of its mission.
Source: The Planetary Postvia NASA