The hunting telescope to the revolutionary planet is dead

The machine to hunt the most prolific planet in history is dead.

The NASA Kepler Space Telescope, which has discovered 70% of the 3,800 extraterrestrial worlds confirmed to date, is running out of fuel, agency officials said on October 30th. Kepler can no longer reorient himself to study cosmic objects or transmit his data to the Earth. The work in this legendary instrument is thus completed after almost a decade. [Kepler’s 7 Greatest Exoplanet Discoveries (So Far)]

And this job has been transformative.

"Kepler has taught us that planets are ubiquitous and incredibly diverse," said Jessie Dotson, a scientist at the Kepler project, based at NASA Ames Research Center in Moffett Field, California, at Space.com. "It changed the way we look at the night sky."

The announcement today was not unexpected. For months, Kepler has been running out of fuel and mission officials have recently made the spacecraft fall asleep to maximize its operational life. But the end can not be forewarned forever; Kepler's tank finally dried up two weeks ago and his life is now officially over.

"This marks the end of Kepler's space operations and scientific data collection," said Paul Hertz, head of NASA's Astrophysics Division, during a teleconference with reporters.

Lead the exoplanet revolution

Kepler was looking for extraterrestrial worlds using the "transit method", discovering the drops in brightness caused by the fact that a planet crosses the face of its star from the point of view of the probe.

These hollows are tiny – so minimal, in fact, that NASA officials were originally dubious that a spacecraft could take such action. The driving force behind Kepler, Bill Borucki of Ames, had four mission proposals rejected in the 1990s before finally breaking through in 2000, after both he and his team demonstrated the sensitivity of the instrument in a test bench on Earth. (Borucki retired in 2015.)

It took a while longer for Kepler to rise. The satellite was launched in March 2009 as part of a $ 600 million mission to assess how Earth-like planets are common in the Milky Way galaxy.

In the beginning, Kepler continually looked at only a small part of the sky, studying about 150,000 stars simultaneously. This work has been incredibly productive, with 2,327 discoveries of exoplanets confirmed to date.

In May 2013, however, the second of Kepler's four "reaction wheels", which maintain orientation, failed. The spacecraft could not maintain enough stability to carry out its ultra-precise transit measurements, and Kepler's original planet hunt ended.

But the spacecraft has not been done. Kepler operators quickly found a way to stabilize it with the sun's pressure, and in 2014, NASA approved a new mission called K2. (It's out of the question to send astronauts to Kepler's service, the spaceship is circling the sun, not the Earth, and is millions of miles away from our planet.)

During K2, Kepler studied various cosmic objects and phenomena, ranging from comets and asteroids in our own solar system to distant supernova explosions, during various 80-day "campaigns." The search for planets has remained an important activity. The K2 Alien-World Hâr is at 354 today.

Kepler's observations during his two missions suggest that planets outnumber the stars of the Milky Way and that potentially Earth-like worlds are common. Indeed, about 20% of the Sun-like stars of our galaxy seem to harbor rocky planets in the habitable zone, the range of distances where liquid water could exist on the surface of the world.

"The legacy of Kepler's exoplanet is absolutely sensational," said Dotson.

But the legacy of the mission also extends to other areas, she said. For example, Kepler's accurate light measurements – that the telescope has done for more than 500,000 stars – help astronomers better understand the inner workings of stars. And the supernova observations of the instrument could dramatically illuminate some of the most dramatic events in the universe.

"We've seen explosions as soon as they happen, at the very beginning," said Dotson. "And it's very exciting if you want to understand why things are going bad," Boom! "

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Not finished yet

Even if Kepler turned a blind eye, the findings of the mission are expected to continue for many years. About 2,900 "candidate" exoplanets detected by the spacecraft have yet to be verified, and most of these should become the real deal, said Kepler team members.

Many other data still need to be analyzed, Dotson said.

And Kepler will continue to live in the revolution of exoplanets that she helped to trigger. For example, in April, NASA launched a new satellite called Transiting Exoplanet Satellite Survey (TESS), which searches for extraterrestrial worlds surrounding stars relatively close to the sun (using the transit method, just like Kepler).

Some of the most promising discoveries of TESS will be examined with NASA's $ 8.9 billion James Webb Space Telescope, which is scheduled to be launched in 2021. Webb will be able to analyze the atmospheres of the extraterrestrial worlds. proximity, looking for methane, oxygen and other gases that may be signs of life.

Kepler's death "is not the end of an era," Charlie Sobeck, a systems engineer at Kepler, also of NASA Ames, told Space.com. "It's an opportunity to score, but it's not an end."

Follow Mike Wall on Twitter @michaeldwall and Google+. follow us @Spacedotcom, Facebook or Google+. Originally posted on Space.com.