VLT/MUSE Characterization of Dimorphos Ejecta from the DART Impact

Abstract

We have observed the Didymos-Dimorphos binary system with the MUSE integral field unit spectrograph mounted at the Very Large Telescope before and after DART impact and captured the ensuing ejecta cone, debris cloud, and tails at subarcsecond resolutions. We targeted the Didymos system over 11 nights from 2022 September 26 to October 25 and utilized both narrow- and wide-field observations with and without adaptive optics, respectively. We took advantage of the spectral–spatial coupled measurements and produced both white-light images and spectral maps of the dust reflectance. We identified and characterized numerous dust features, such as the ejecta cone, spirals, wings, clumps, and tails. We found that the base of the sunward edge of the wings, from October 3 to 19, is consistent with maximum grain sizes on the order of 0.05–0.2 mm and that the earliest detected clumps have the highest velocities, on the order of ;10 m s−1. We also see that three clumps in narrow-field mode (8″ × 8″) exhibit redder colors and slower speeds, around 0.09 m s−1, than the surrounding ejecta, likely indicating that the clump is composed of larger, slower grains. We measured the properties of the primary tail and resolved and measured the properties of the secondary tail earlier than any other published study, with first retrieval on October 3. Both tails exhibit similarities in curvature and relative flux; however, the secondary tail appears thinner, which may be caused by lower-energy ejecta and possibly a low-energy formation mechanism such as secondary impacts.