Ground-based observability of Dimorphos DART impact ejecta: photometric predictions

The Double Asteroid Redirection Test (DART) is a NASA mission intended to crash a projectile on Dimorphos, the secondary component of the binary (65803) Didymos system, to study its orbit deflection. As a consequence of the impact, a dust cloud will be be ejected from the body, potentially forming a transient coma- or comet-like tail on the hours or days following the impact, which might be observed using ground-based instrumentation. Based on the mass and speed of the impactor, and using known scaling laws, the total mass ejected can be roughly estimated. Then, with the aim to provide approximate expected brightness levels of the coma and tail extent and morphology, we have propagated the orbits of the particles ejected by integrating their equation of motion, and have used a Monte Carlo approach to study the evolution of the coma and tail brightness. For typical power-law particle size distribution of index –3.5, with radii rrmin = 1 μm and rmax = 1 cm, and ejection speeds near 10 times the escape velocity of Dimorphos, we predict an increase of brightness of ∼3 magnitudes right after the impact, and a decay to pre-impact levels some 10 d after. That would be the case if the prevailing ejection mechanism comes from the impact-induced seismic wave. However, if most of the ejecta is released at speeds of the order of ≳100 m s−1, the observability of the event would reduce to a very short time span, of the order of 1 d or shorter.FM acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). FM also acknowledges financial support from the Spanish Plan Nacional de Astronomía y Astrofísica LEONIDAS project RTI2018-095330-B-100, and project P18-RT-1854 from Junta de Andalucía. ACB and PYL acknowledge funding by the SU-SPACE-23-SEC-2019 EC-H2020 NEO-MAPP project (GA 870377). ACB also acknowledges funding by the Spanish Ministerio de Ciencia e Innovación RTI2018-099464-B-I00 project. GT and BD acknowledge finantial support from project FCE-1-2019-1-156451 of the Agencia Nacional de Investigación e Innovación ANII (Uruguay)