Free Astronomy Magazine May-June 2023

43 MAY-JUNE 2023 ASTRO PUBLISHING created from,” says Brian Murphy, a PhD student at the University of Ed- inburgh in the UK and co-author of one of the studies. Studying the cloud of material ejected after DART’s impact can therefore tell us about how our Solar System formed. “Impacts between asteroids hap- pen naturally, but you never know it in advance,” continues Cyrielle Opitom, an astronomer also at the University of Edinburgh and lead au- thor of one of the articles. “DART is a really great opportunity to study a controlled impact, almost as in a lab- oratory.” Opitom and her team followed the evolution of the cloud of debris for a month with the Multi Unit Spec- troscopic Explorer (MUSE) instru- ment at ESO’s VLT. They found that the ejected cloud was bluer than the asteroid itself was before the im- pact, 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 Opitom’s team to break up the light from the cloud into a rainbow-like pattern and look for the chemical fingerprints of dif- ferent gases. In particular, they searched for oxygen and water com- ing from ice exposed by the impact. But they found nothing. T his video shows the evolution of the cloud of debris that was ejected after NASA’s DART spacecraft collided with the asteroid Dimorphos. The anima- tion is based on a series of images taken with the MUSE instrument on ESO’s Very Large Telescope (VLT) for one month after the impact. The first image was taken on 26 September 2022, just before the impact, and the last one was taken almost one month later on 25 October. Over this period several structures devel- oped: clumps, spirals, and a long tail of dust pushed away by the Sun’s radiation. Dimorphos orbits a larger asteroid called Didymos, but they can’t be discerned in these images. The background streaks seen here are due to the apparent move- ment of the background stars during the observations while the telescope was tracking the asteroid pair. [ESO/Opitom et al.]