Momentum Transfer from the DART Mission Kinetic Impact on Asteroid Dimorphos

分类： 天文学 >> 天文学 提交时间： 2023-02-19

Andrew F. Cheng Harrison F. Agrusa Brent W. Barbee Alex J. Meyer Tony L. Farnham Sabina D. Raducan Derek C. Richardson Elisabetta Dotto Angelo Zinzi Vincenzo Della Corte Thomas S. Statler Steven Chesley Shantanu P. Naidu Masatoshi Hirabayashi Jian-Yang Li Siegfried Eggl Olivier S. Barnouin Nancy L. Chabot Sidney Chocron Gareth S. Collins

摘要： The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period, we find an instantaneous reduction in Dimorphos's along-track orbital velocity component of 2.70 +/- 0.10 mm/s, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact. For a Dimorphos bulk density range of 1,500 to 3,300 kg/m$^3$, we find that the expected value of the momentum enhancement factor, $\beta$, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg/m$^3$, $\beta$= 3.61 +0.19/-0.25 (1 $\sigma$). These $\beta$ values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos.

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