The voluntary collision of a NASA machine with the Asteroid Dimorphos has reduced its orbit around his companion Didymos by thirty-two minutes.
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The verdict has fallen and he fills with joy the specialists of what, in the world of astronomy and space, we call “planetary defense” – understand “the parades against threats from the cosmos”. Tuesday, October 11, NASA made public the result of the collision between its vessel-kamikaze Dart (Double Asteroid Redirection Test) and the small asteroid Dimorphos: by hitting at the speed of 22,000 kilometers per hour this big pebble of 160 meters Diameter, on September 27, the probe of half-tonne managed to deviate slightly from its trajectory. A crucial test to learn to protect the land from a possible asteroid that would go straight to it and whose impact would have cataclysmic consequences.
How did we determine this result, even though the meeting occurred at 11 million kilometers and, at this distance, Dimorphos is only a dust which we did not even know the form Before Dart approached? To understand this, you should know that Dimorphos does not travel alone, that he is the satellite of a larger asteroid, called Didymos. Thanks to a remarkable coordinated observation campaign which involved around forty terrestrial and space telescopes -for the occasion, the James -Webb space telescope and its Hubble ancestor have for the first time aimed at the same target -, astronomers have measured the Dimorphos revolution period around Didymos after the impact. This went from eleven hours and fifty-five minutes to eleven and twenty-three minutes, a reduction of thirty-two minutes, which implies that the satellite asteroid has actually got closer to its companion.
“Beyond our expectations”
These thirty-two minutes are much higher than sixty-three seconds on which the scientists, very cautious, tamed at the start. “This difference of sixty-three seconds was a minimum gap, calculated in the event that Dart has sunk in Dimorphos as in plasticine, without ejection of matter, explains Patrick Michel, CNRS research director at the Observatory From the Côte d’Azur and specialist in asteroids. But as soon as you eject matter, the action-reaction principle comes into play: what goes in one direction pushes in the other. “The more the collision propelled From the rock in space, the more we moved from the sixty-three seconds. “A wide range of values was therefore possible,” continues Patrick Michel. We expected rather nineteen minutes, but a gap of thirty-two minutes was one of the possibilities. It was therefore beyond our expectations without be beyond our predictions. “
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