On September 26, 2022, NASA’s DART spacecraft collided with the asteroid Dimorphos in a controlled test of our asteroid deflection capabilities. The impact took place 11 million km away from Earth, close enough to be observed in detail with many telescopes. All four 8.2-m telescopes of ESO’s Very Large Telescope observed the aftermath of the impact, and the first results of these observations have now been published in two papers in the journal Astronomy & Astrophysics and the Astrophysical Journal Letters.
“Asteroids are some of the most basic relics of what all the planets and moons in our Solar System were created from,” said Brian Murphy, a Ph.D. student at the University of Edinburgh.
Studying the cloud of material ejected after DART’s impact can therefore tell us about how our Solar System formed.
“Impacts between asteroids happen naturally, but you never know it in advance,” said Dr. Cyrielle Opitom, an astronomer at the University of Edinburgh.
“DART is a really great opportunity to study a controlled impact, almost as in a laboratory.”
In their study, Murphy, Dr. Opitom and colleagues followed the evolution of the cloud of debris for a month with the Multi Unit Spectroscopic Explorer (MUSE) instrument on ESO’s Very Large Telescope (VLT).
They found that the ejected cloud was bluer than the asteroid itself was before the impact, indicating that the cloud could be made of very fine particles.
In the hours and days that followed the impact other structures developed: clumps, spirals and a long tail pushed away by the Sun’s radiation.
The spirals and tail were redder than the initial cloud, and so could be made of larger particles.
MUSE allowed the astronomers to break up the light from the cloud into a rainbow-like pattern and look for the chemical fingerprints of different gases.
In particular, they searched for oxygen and water coming from ice exposed by the impact. But…
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