RIP Kepler: NASA's exoplanet-hunting space telescope is finally dead

NASA Administrator Jim Bridenstine in a file image the US space agency's Kepler space telescope has run out of fuel and is being retired after nine years

The Kepler space telescope's end has finally come

A new, state-of-the-art planet hunter - the Transiting Exoplanet Survey Satellite, or TESS - was launched last April.

A replacement: Several exoplanet-hunting missions are in the works, including the James Webb Space Telescope, now due to launch in 2021 after a series of delays. Its ability to point at distant stars and identify possible alien worlds worsened dramatically at the beginning of October, but flight controllers still managed to retrieve its latest observations.

The telescope has now gone silent.

During its nine-year mission, Kepler found more than 2,600 planets orbiting stars outside the solar system -including many with the potential for harboring life.

Between its launch in March 2009 and May 2013 Kepler discovered 2,327 exoplanets, outside the Sun's solar system, by studying 150,000 stars whilst looking at a small area of sky.

But the telescope has now run out of the fuel needed for further operations. Take, for example, Kepler-22b, which he calls one of the most interesting planets in the batch.

"And because of Kepler, we know that solar systems come in a variety of configurations completely unlike our own, solar systems with Jupiters orbiting their stars in only a few days, solar systems with small, rocky planets packed inside the orbit of Mercury, so close that the planets are in resonance with each other".

"In the end, we didn't have a drop of fuel left over for anything else", Charlie Sobeck, project system engineer at NASA's Ames Research Center, said during a teleconference.

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. It also showed us the diversity of planets and planetary systems out there, some of which are very different than ours.

Bill Borucki, the mission's retired principal investigator, compared the task to "trying to detect a flea crawling across a vehicle headlight when the auto was 100 miles away".

NASA has tallied the number of exoplanets that Kepler has discovered at 2,681. "We're confident that TESS is going to find thousands more planets, just like Kepler did".

"I'm excited about the diverse discoveries that are yet to come from our data and how future missions will build upon Kepler's results".

The resurrected mission became known as K2 and yielded 350 confirmed exoplanets.

"I think we were all extremely impressed with what it was doing for us", Borucki said of Kepler.

"We have shown there are more planets than stars in our galaxy, that many of these planets are roughly the size of the Earth and some, like the Earth, are at the right distance from their star that there could be liquid water on the surface, a situation conducive to the existence of life", Borucki said.

Another longtime spacecraft chasing odd worlds in our own solar system, meanwhile, is also close to death.

In June of 2016 NASA announced that K2 would be extended by three years - which placed it beyond the spacecraft's fuel reserves. From 2011 to 2012, Dawn studied the asteroid Vesta before pulling off an unprecedented maneuver by leaving orbit and traveling to the dwarf planet Ceres, which it observed for over 3.5 years. And recent glitches with the 28-year-old Hubble Space Telescope and the 19-year-old Chandra X-Ray Observatory have signaled that those grand-scale telescopes are past their prime, mechanically if not scientifically. The agency said it's chose to retire the spacecraft within its current, safe orbit, away from Earth. The sequence of commands for doing so has been transmitted to the spacecraft, awaiting a final command from the ground to run them.

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