Nine years of good and loyal services in our universe. The mission of the Kepler space telescope has come to an end, after his long journey around the Sun, and the discovery of more than 2600 planets outside our solar system, announced by Nasa on Tuesday.

Imagined 35 years ago, at a time when no planet was known outside of the solar system, Kepler’s mission was to find planets sisters of the Earth, that is to say, of a comparable size, the rocky and non-carbonated, and at a distance neither too close nor too distant from their star. At a distance where liquid water could, as on Earth, to be present in surface -and, therefore, likely to house life.

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Launched in 2009, the telescope was named in honour of the German astronomer Johannes Kepler.

The telescope has been focused on two constellations of the milky Way, the Swan and the Lyre, with millions of stars in its objective, the resolution of which was extraordinary at the time of its design. The goal was so sensitive that it could detect the tiny drop in light intensity caused by the passage of a planet in front of its star.

To the discovery of other planets

In January 2010, comes the discovery of the first five planets, named Kepler 4b, 5b, etc., But they are soft. The first rocky planet was announced in January 2011, Kepler-10b. But it is so close to its star that one of its faces is probably molten, a world of lava. The first planet is potentially habitable is the number 22b. Liquid water is found there may be. In 2014, finally, the true first cousin of the Earth is marked: number 186f, 580 light-years.

Kepler-452b, another candidate for extraterrestrial life. Image released by Nasa in July 2015.

REUTERS/NASA/Ames/JPL-Caltech/T. Pyle/Handout

hundreds of discoveries follow and revolutionize our knowledge of the galaxy. They confirm that the Earth is, finally, not an exception of the galaxy. Thanks to Kepler, we also know that there are more planets than stars in the milky Way. Most have a size between that of Earth and that of Neptune.

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according To the observations of the telescope, astronomers now believe that 20 to 50% of the stars visible from the Earth at night are likely to have small Land in orbit around them, at a distance where lakes and oceans, can in theory form.

The telescope has also discovered strange, as these systems where up to eight planets crowd into a orbit compact around their star. Or the planet Kepler-16b, which orbits around two stars… and where, such as on Tatooine, a fictional planet from Star Wars – the inhabitants could attend a double setting suns, if Kepler-16b was not gas.

mechanical Problems and a shortage of gasoline

Kepler has encountered several obstacles on its road space. In 2013, mechanical problems, rush to the end of the original mission of the telescope, which initially was to last three and a half years. But engineers at Nasa found an ingenious system to keep the stabilize.

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a few weeks ago, the fuel of the telescope is reduced to a very low level. Kepler has solar panels but these do not feed into that electronic equipment on board. It took 12 kg of fuel in 2009 for its engine, which was used to correct the drifts and control the orbit. The engineers knew that the mission could not last forever.

For the hunt for exoplanets, the torch is picked up by the satellite of the Nasa TESS, launched last April.

The telescope, now turned off, will stay on its orbit, said Nasa. In forty years, it is closer to the Earth, without the risk of crashing.

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The astronomers will still probably years to analyze the images taken by Kepler.