"As the first NASA's research mission of other planets, Kepler has greatly exceeded our expectations and opened the way to our exploration and search for extraterrestrial life in the Solar System and beyond", said Thomas Zurbuchen, head of NASA's scientific direction.
Both the Kepler telescope, which identified more than 2,600 alien planets, and the Dawn spacecraft, which visited the asteroid Vesta and the dwarf planet Ceres, ended because they no longer had enough gas in the tank.
Launched into space on March 6, 2009, the Kepler telescope combined techniques to measure stellar brightness with the largest digital camera equipped for observations of outer space at that time. Before the mission, our knowledge of planets outside our solar system that orbit a star was woefully lacking.
Four years into the mission, after the primary mission objectives had been met, some mechanical failures temporarily halted observations. The knowledge that there are planets scattered everywhere opens almost endless possibilities, and keeps pushing expectations for Kepler's successor TESS and other upcoming missions.
Kepler, which launched in 2009, discovered 2,600 of the 4,000 confirmed exoplanets now known. Indeed, one challenge for astronomers who want to study the properties of Kepler planets is that Kepler itself is often the best instrument to use. The mission team was able to devise a fix, switching the spacecraft's field of view roughly every three months. Ceres and Vesta are important to the study of distant planetary systems, too, as they provide a glimpse of the conditions that may exist around young stars,"said mission principal investigator Carol Raymond of NASA's Jet Propulsion Laboratory (JPL) in a NASA news release". The data from the extended mission were also made available to the public and science community immediately, allowing discoveries to be made at an incredible pace and setting a high bar for other missions.More news: Oceans Are Absorbing Much More Heat Than Expected, Says Study
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Kepler became the most effective exoplanet hunter thanks to its powerful ability to keep a close watch on light emission patterns from thousands of stars in the Milky Way.
An artist's concept of NASA's Kepler spacecraft.
The founder of the Kepler mission, William Borucki, recalled that when this idea was conceived 35 years ago, humanity "did not know of a single planet" outside the solar system.
With Kepler retiring after an illustrious planet-hunting career, a new telescope will take its place.
NASA's Ames Research Center in California's Silicon Valley manages the Kepler and K2 missions for NASA's Science Mission Directorate.