近日，意大利国家天体物理研究所的E. Dotto及其研究团队取得一项新进展。经过不懈努力，他们利用LICIACube揭示Dimorphos喷出物的羽流特性。相关研究成果已于2024年2月28日在国际权威学术期刊《自然》上发表。

该研究团队公布了DART撞击前15天部署的LICIACube立方体卫星上LUKE和LEIA仪器的观测数据。这些数据是从撞击前71秒至撞击后320秒期间收集的。观测结果显示，喷出的物质形成了锥状的羽流，其孔径角为140±4度。羽流的内部区域呈现蓝色，而随着距离Dimorphos的增远，颜色逐渐变为红色。羽流结构复杂且不均匀，主要由细丝、尘埃颗粒以及单个或群集的岩石组成。喷出物的速度也有所不同，从每秒几十米到每秒500米不等。

据悉，双小行星重定向测试（DART）于2022年9月26日成功与Didymos小行星的卫星Dimorphos相撞。地面观测数据表明，撞击后，由于喷出的物质，Didymos系统的亮度增加了8.3倍。然而，仅仅23.7天后，其亮度就恢复到了撞击前的水平。从撞击后的15分钟到18.5天，哈勃太空望远镜以每像素2.1公里的高空间分辨率进行了持续观测，揭示了喷出物的复杂演变过程，这与其他小行星撞击事件的结果相一致。此外，通过测量二元周期变化确定的动量增强因子，其值介于2.2和4.9之间，具体数值取决于对Dimorphos的质量和密度的不同假设。

附：英文原文

Title: The Dimorphos ejecta plume properties revealed by LICIACube

Author: Dotto, E., Deshapriya, J. D. P., Gai, I., Hasselmann, P. H., Mazzotta Epifani, E., Poggiali, G., Rossi, A., Zanotti, G., Zinzi, A., Bertini, I., Brucato, J. R., DallOra, M., Della Corte, V., Ivanovski, S. L., Lucchetti, A., Pajola, M., Amoroso, M., Barnouin, O., Campo Bagatin, A., Capannolo, A., Caporali, S., Ceresoli, M., Chabot, N. L., Cheng, A. F., Cremonese, G., Fahnestock, E. G., Farnham, T. L., Ferrari, F., Gomez Casajus, L., Gramigna, E., Hirabayashi, M., Ieva, S., Impresario, G., Jutzi, M., Lasagni Manghi, R., Lavagna, M., Li, J.-Y., Lombardo, M., Modenini, D., Palumbo, P., Perna, D., Pirrotta, S., Raducan, S. D., Richardson, D. C., Rivkin, A. S., Stickle, A. M., Sunshine, J. M., Tortora, P., Tusberti, F., Zannoni, M.

Issue&Volume: 2024-02-28

Abstract: The Double Asteroid Redirection Test (DART) had an impact with Dimorphos (a satellite of the asteroid Didymos) on 26 September 2022. Ground-based observations showed that the Didymos system brightened by a factor of 8.3 after the impact because of ejecta, returning to the pre-impact brightness 23.7days afterwards. Hubble Space Telescope observations made from 15minutes after impact to 18.5days after, with a spatial resolution of 2.1kilometres per pixel, showed a complex evolution of the ejecta, consistent with other asteroid impact events. The momentum enhancement factor, determined using the measured binary period change, ranges between 2.2 and 4.9, depending on the assumptions about the mass and density of Dimorphos. Here we report observations from the LUKE and LEIA instruments on the LICIACube cube satellite, which was deployed 15days in advance of the impact of DART. Data were taken from 71seconds before the impact until 320seconds afterwards. The ejecta plume was a cone with an aperture angle of 140±4 degrees. The inner region of the plume was blue, becoming redder with increasing distance from Dimorphos. The ejecta plume exhibited a complex and inhomogeneous structure, characterized by filaments, dust grains and single or clustered boulders. The ejecta velocities ranged from a few tens of metres per second to about 500metres per second.

DOI: 10.1038/s41586-023-06998-2

Source: https://www.nature.com/articles/s41586-023-06998-2