The first image came on Monday, just hours after impact, you project ATLAS, a telescope in South Africa. We see there, literally, an explosion: while the asteroid Didymos passes in the field of the image, occurs what resembles an enormous burst of light: it is the impact.
Didymos, however, is not even the place of impact. This asteroid about 800 meters wide is accompanied by a moon, Dimorphos, which was the target of DART. Just 160 meters wide, this moon is too small to be seen in the image. But the force of the impact was enough to produce a cloud of debris – and that’s what gives this burst of light: in a few minutes, the brightness was multiplied by 10, result of the sun’s rays reflecting on trash. The telescope took a photo every 40 seconds.
ATLAS, which means Asteroid Terrestrial-impact Last Alert System, was not pointed at this region of the sky by chance. It is part of a network of four telescopes around the world that scan the skies for new asteroids that could collide with Earth.
But even for these experts of the thing, the size of the cloud of debris was a surprise, report it New York Times“We didn’t expect to see such a big column of dust coming out,” explains astronomer John Tonry, from the University of Hawaii, and co-director of ATLAS. “Within an hour, this cloud was as big as the Earth. Astronomers expect the debris to take a few weeks to fall back on Dimorphos.
Other images arriving from other telescopes in the southern hemisphere are less spectacular, but the simple fact of having seen something at this distance testifies to the force of the impact. For example, another South African telescope (South African Astronomical Observatoryor SAAO) captured the same luminous glow. The Italian Virtual Telescope project has published a sequence of similar images.
Live from space
A different set of images, however, came from space and is directly related to the DART mission. This is the small Italian probe LICIACube, which is barely the size of a shoebox, and whose mission was to follow DART. His view of the debris cloud is therefore more detailed: his photos show it asymmetric, which could be explained by the angle at which DART crashed or by the morphology of the ground.
Other photos have also come from space, but closer to Earth: the James-Webb and Hubble telescopes. It was not obvious for the first, which is not designed to detect moving objects. But in his case, it is possible that his instruments will help to learn more about the chemical composition of the asteroid.
As for Hubble, it was unlucky to have Earth between Dimorphos and it at the time of impact, but it took pictures afterwards, showing the expanding cloud of debris.
In theory, all this data on the dust column or plume should help to learn more about the structure and composition of Dimorphos. But ultimately, it is the impact that this collision will have on the orbit of this “moon” around its asteroid – 11 hours and 55 minutes for the moment – which remains the raison d’être of the mission. A change, however small, could reveal how much force would be needed to divert an asteroid from its course towards us – if such an operation ever proves necessary.