Origin of the configuration diversity of binary asteroids
Speaker: Wenyue Dai (NAOJ)
Abstract:
Binary asteroid systems are ubiquitous in the observed asteroid population. Many small binary asteroid systems are thought to originate from the rotational breakup, where the spin-up of a primary asteroid triggers mass shedding, creating a transient debris disk that finally re-accumulates to form satellite(s). In this scenario, a prolate satellite in a compact orbit is expected from theoretical predictions. However, recent space missions have revealed a remarkable diversity of binary configurations. One striking anomaly is the (152830) Dinkinesh system, which hosts a contact-binary satellite named Selam in a wide orbit. Here, we propose a unified framework for reconstructing the formation pathways of binary systems. We find that if multiple episodes of mass shedding and multi-generations of satellites are considered, the pre-existing satellite can strongly influence the subsequent satellite formation. Taking into account the orbital migration of the pre-existing satellite, this leads the system evolution after a subsequent mass shedding to different pathways, where the observed diversity in binary asteroid configurations can be naturally produced. We suggest that the dynamical histories of the Dinkinesh system and some triple systems involve multiple mass shedding and inter-satellite interaction. We also find that ~44% of the known binaries have configurations indicative of multi-satellite histories, suggesting a greater diversity of binary asteroid configurations to be revealed in the future.