The most successful planet hunter in history is dead.
NASA's Kepler Space Telescope, which has detected 70 percent of the previously 3,800 confirmed alien worlds, has run out of fuel. 30). Kepler can no longer reorient himself to study cosmic objects or beam his data to Earth, so that the work of the legendary instrument is completed in almost a decade.
And this work was transformative. [Kepler’s 7 Greatest Exoplanet Discoveries (So Far)]
"Kepler has taught us that planets are omnipresent and unbelievably diverse," said Kepler Project Scientist Jessie Dotson of the NASA Ames Research Center in Moffett Field, California, opposite Space.com. "It has changed how we see the night sky."
Today's announcement was not unexpected. Kepler has been running low on fuel for months, and the mission directors have recently put the spacecraft to sleep several times to maximize uptime. But the end could not be prevented forever; Kepler's tank is finally dry two weeks ago and his life is officially over.
"This marks the end of Kepler's spacecraft operations and the end of the collection of scientific data," Paul Hertz, director of NASA's Astrophysics Department, told reporters during a conference call today.
Leading the Exoplanet Revolution
Kepler used the "transit method" to hunt for alien worlds and found the brightness drops that occur when a planet crosses the face of its star from the spaceship's perspective.
These dips are tiny ̵
It took Kepler a while to get airborne. The spacecraft launched in March 2009 on a $ 600 million mission to gauge how ordinary Earth-like planets are located throughout the Milky Way.
Initially, Kepler stared steadily at a single small sky and at the same time studied about 150,000 stars. This work was incredibly productive and has yielded 2,327 confirmed exoplanets.
In May 2013, however, the second of Kepler's four landmark "reaction wheels" failed. The spacecraft could not hold itself stable enough to carry out its ultra-precise transit measurements, and Kepler's original planet hunt came to an end.
But the spacecraft was not finished yet. Kepler's handlers soon discovered how they could stabilize it using sunlight, and in 2014, NASA approved a new mission called K2. (To send astronauts to serve Kepler is out of the question, the spacecraft orbiting the sun, not the Earth, is millions of miles from our planet.)
During K2, Kepler studied a variety of cosmic objects and comet phenomena and asteroids in our own solar system to distant supernova explosions during various 80-day "campaigns". The planet hunt remained a significant activity; The K2 Alien World Haul is now at 354.
Kepler's observations on both missions indicate that planets exceed the number of stars in the Milky Way and that potentially earth-like worlds are prevalent. In fact, about 20 percent of Sun-like stars in our galaxy seem to harbor rocky planets in the habitable zone, the distance that liquid water could exist on the Earth's surface.
"Kepler's exoplanet legacy is absolutely blockbuster," Dotson
But the legacy of the mission extends to other areas, she emphasized. For example, Kepler's precise brightness measurements-which the telescope has completed for more than 500,000 stars-help astronomers better understand the inner workings of stars. And the supernova observations of the instrument could shed considerable light on some of the most dramatic events in the universe.
"We've seen explosions as they happen, at the very beginning," said Dotson. "And that's very exciting if you want to find out why things are going," Boom! "
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Not finished yet
Even though Kepler has his eyes closed, discoveries from the mission should continue to roll in the coming years. Some 2,900 "candidate" exoplanets discovered by the spacecraft are still under review, and most of them should ultimately be the true deal, Kepler team members said.
A lot of other data needs to be analyzed, Dotson said
and Kepler will live on in the exoplanet revolution that has helped. For example, in April, NASA launched a new spacecraft called the Transit Exoplanet Survey Satellite (TESS), which is hunting for alien worlds that are relatively close to the Sun (much like Kepler using the transit method).
Some of TESS's most promising finds are being investigated by NASA's $ 8.9 billion James Webb Space Telescope, due to launch in 2021. Webb will be able to browse the atmospheres of nearby alien worlds for methane, oxygen and other gases sign of life.
Kepler's death "is not the end of an era," said Kepler's systems engineer Charlie Sobeck, also from NASA Ames, opposite Space.com. "It's an opportunity to mark, but it's not an end."