"As NASA's first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond", Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington, said in a statement. "I had no trouble believing that there were planets out there of all different kinds, so I had to wonder, why did it affect me so much when Kepler showed that there were lots of planets out there everywhere?" he said during the news conference.
Kepler's discoveries have shed a new light on mankind's place in the Universe.
NASA launched the Kepler telescope on March 6, 2009, to learn if Earth-like planets that might harbour life are common or rare in other star systems.
One of the big conclusions is that there may be well more planets than stars in the Milky Way, thanks to the number of multiple-planet systems found by Kepler.
Thanks to Kepler's data, which was all safely beamed back to Earth before the end of the mission, we now know that planets are, in fact, exceedingly common.
Kepler allowed astronomers to discover that 20% to 50% of the stars we can see in the night sky are likely to have small, rocky, Earth-size planets within their habitable zones - which means that liquid water could pool on the surface, and life as we know it could exist on these planets. TESS, the Transiting Exoplanet Survey Satellite, launched in April and is the newest planet hunter for NASA. Take, for example, Kepler-22b, which he calls one of the most interesting planets in the batch.
The space agency says it has chose to retire Kepler while it is located in its present orbit, which it describes as safe and away from Earth.
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Kepler discovered 2,681 planets outside our solar system and even more potential candidates.
The artist's concept depicts Kepler-69c, a super-Earth-size planet in the habitable zone of a star like our sun, located about 2,700 light-years from Earth in the constellation Cygnus. Over the life of the mission, more than 100,000 of those stars were actively monitored by Kepler.
The end came just a few months shy of the 10th anniversary of Kepler's 2009 launch. In all, Kepler surveyed more than 500,000 stars.
Kepler discovered thousands of planets, many of them similar in size to the Earth (far right), though how they might appear is still a matter of speculation.
Nearly lost in 2013 because of equipment failure, Kepler was salvaged by engineers and kept peering into the cosmos, thick with stars and galaxies, ever on the lookout for dips in in the brightness of stars that could indicate an orbiting planet.
Kepler used a detection method called transit photometry, which looked for periodic, repetitive dips in the visible light of stars caused by planets passing, or transiting, in front of them. "I'm excited about the diverse discoveries that are yet to come". The spacecraft itself is fine, by all accounts; rather, it no longer has any fuel left to continue powering its operations.
"Because of Kepler, what we think about our place in the universe has changed", said Hertz.
Since that time, NASA changed the craft's mission to adjust to the telescope's new normal, calling the updated mission K2.