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The Evolution of Dimorphos’s Tail in the Hubble Space Telescope Observations

Presentation #510.04 in the session Asteroids: Planetary Defense (Oral Presentation)

Published onOct 23, 2023
The Evolution of Dimorphos’s Tail in the Hubble Space Telescope Observations

Following the successful impact of the DART (Double Asteroid Redirection Test) spacecraft into Dimorphos, the secondary of the Didymos binary asteroid system, on September 26, 2022, a dust tail formed from the low-speed ejecta due to solar radiation pressure. This tail remained visible for many months after the impact and showed an overall straight and narrow morphology that resembles the tails of other serendipitously discovered active asteroids thought to be triggered by dust release from natural impact or rotation. In this sense, the DART impact artificially created an active asteroid. The observations of the tail of Dimorphos provided the first opportunity to fully characterize the formation and evolution of such an active asteroid tail with the best knowledge of the mass shedding event, providing a unique context for interpreting the observations of natural active asteroids. Additionally, the release of dust from the secondary asteroid in the binary system Didymos caused some unusual dynamic processes that affected the morphology and evolution of the tail. We performed an imaging campaign to observe the tail from shortly after the impact through July 6, 2023, with the Hubble Space Telescope WFC3/UVIS instrument through the F350LP filter to characterize the morphology and evolution of the tail. Observations suggested that the tail was dominated by dust released within one week after the impact. There was evidence for the release of mm-sized dust up to eight weeks after impact. A simple dust dynamical model suggested that the persistence of such a tail requires the ejection of particles of micrometers up to several cm in size at speeds comparable to the escape velocity of the Didymos system at Dimorphos’s surface. We will report the results from our campaign in the 9.3 months after the DART impact, and discuss the implications.

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