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Detached particles in the environment of (65803) Didymos NEA binary system

Presentation #113.06 in the session “Didymos: Throwing DARTs”.

Published onOct 03, 2021
Detached particles in the environment of (65803) Didymos NEA binary system

(65803) Didymos is a binary asteroid that orbits the Sun at 1.64 AU and is the target of the DART (NASA) and Hera (ESA) missions. The system is made up of a 780 m diameter primary body, Didymos, and a 160 m satellite, called Dimorphos. The primary is a fast rotator (2.26 h) and has a low density (2170 kg/m3) typical of gravitational aggregates or “rubble-piles" asteroids [1]. Besides, Didymos is a top-shaped asteroid: it has an oblate spheroidal shape with an equatorial bulge, such as (162173) Ryugu [2], (101955) Bennu [3], etc. The rotational period of fast spinning asteroids can be close to the structural stability limit and they are kept together by the shear forces generated by friction between their components. However, if the local centrifugal acceleration near the equatorial regions is large enough to overcome local gravity, then regolith can leave the surface [4] [5]. In this work, we study the dynamics of the particles that are ejected from the surface of Didymos. The analysis is carried out from the development of a numerical code that integrates the particles’ equation of motion in a rotating frame of reference, centered on the primary asteroid. A polyhedral shape model for Didymos is considered, formed by 1000 vertices and 1996 triangular faces, in which centers particles are placed. We take into account the action of the gravitational field of Didymos, that of the secondary, the gravitational force of the Sun, and the solar radiation pressure. The environment of the asteroid is studied by computing the radial density of particles and their trajectories. References: [1] Benner, L. A. et al. Radar imaging and a physical model of binary asteroid 65803 Didymos. Bull. Am. Astron. Soc. 42, 1056 (2010). [2] Watanabe, S. et al. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—a spinning top-shaped rubble pile. Science 364, 268–272 (2019). [3] Lauretta, D. S. et al. The unexpected surface of asteroid (101955) Bennu. Nature 568, 55–60 (2019). [4] Campo Bagatin, A. 2013. Small Asteroids with “Dusty” Atmospheres?. Lunar and Planetary Science Conference. [5] Yu, Y., Michel, P., Hirabayashi, M., Richardson,D. C. 2019. The expansion of debris flow shed from the primary of 65803 Didymos. Monthly Notices of the Royal Astronomical Society 484, 1057–1071. doi:10.1093/mnras/sty3515

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