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The mission of the Kepler Space Telescope has ended after nine years in orbit around the Sun and the discovery of more than 2,600 planets out of our solar system, NASA announced Tuesday.
Imagined 35 years ago, at a time when no planet was known outside the solar system, Kepler's mission was to discover planets sister to Earth, that is to say, of comparable size rocky and non-aerated, and at a distance neither too close nor too far from their star. At a distance where the liquid water could, as on the Earth, be present on the surface – and thus likely to harbor life.
Launched in 2009, the telescope was named in honor of German astronomer Johannes Kepler.
The telescope had been pointed at two constellations of the Milky Way, those of the Swan and the Lyre, with millions of stars in its objective, at an extraordinary resolution for the time of its conception.
The lens was so sensitive that it could detect the tiny drop in light intensity caused by the pbadage of a planet in front of its star.
In January 2010 comes the discovery of the first five planets, named Kepler 4b, 5b, etc. But they are gaseous.
The first rocky planet is announced in January 2011, Kepler-10b. But she is so close to her star that one of her faces is probably melting, a lava world.
The first habitable planet is number 22b. Liquid water may be there. And in 2014, finally, the first real cousin of the Earth, number 186f, at 580 light-years.
Hundreds of discoveries will follow and revolutionize our knowledge of the galaxy. They will confirm that the Earth is, ultimately, not a galactic exception.
Thanks to Kepler, we also know that there are more planets than stars in the Milky Way. Most are between Earth and Neptune.
According to Kepler's observations, astronomers now estimate that 20 to 50% of the stars visible from Earth at night are likely to have small Earths orbiting them at a distance where lakes and oceans can theoretically form.
The telescope has also made strange discoveries, like those systems where up to eight planets crowd into a compact orbit around their star.
Or the planet Kepler-16b, which revolves around two stars … and where, as on Tatooine, a fictional planet of Star Wars, the inhabitants could attend a double sunset, if Kepler-16b was not carbonated .
– Predictable end –
As for the death of great scientists, tributes immediately rained.
"Not only did he show us how many planets could exist in space, he also opened up a completely new and serious field of research that stormed the scientific community," said Thomas Zurbuchen, division director. from scientific research to NASA.
And as for some deaths, Kepler's death was not really a surprise.
In 2013, mechanical problems had precipitated the end of the telescope's original mission, which initially only lasted three and a half years. But NASA engineers had found an ingenious system to continue to stabilize it to keep it running.
A few weeks ago, the fuel had dropped to a very low level. Kepler has solar panels but these only feed his electronics on board.
He had carried 12 kg of fuel in 2009 for his engine, which was used to correct drift and control the orbit, and engineers knew that the mission could not last forever.
The telescope, now off, will stay in its orbit, said NASA. In about forty years, its orbit will bring it closer to the Earth, but without ever risking to crash into it.
As for the hunt for exoplanets, the torch will be taken over by the NASA TESS satellite launched last April.
But astronomers will probably spend years badyzing the clichés taken by Kepler until the end.
"Kepler took us on a new adventure," said William Borucki, who was the first head of the mission.
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