Formation paths of binary asteroid systems born from YORP deformation

Many binary asteroid systems (‘Binary systems’) are believed to originate from Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) deformation; that is, the YORP spin-up of an asteroid triggers the rotational failure, and the material shed from the main body finally reaccumulates and forms its satellite(s). A binary system can form from a single YORP shedding event (‘SSh’), or from a sequence of such events (‘MultiSh’). In the latter one, a satellite formed in the first shedding event, thereby in the subsequent shedding events the evolution of shed material is influenced by the presence of this first-generation satellite. These different scenarios can result in various final configurations of binary systems. We aim to systematically investigate this relevance, and thereby obtain a ‘map’ of the various formation paths of binary systems.

Our work primarily focuses on the MultiSh scenario, which is rarely concerned in previous works. We use 2 dimensionless parameters to characterize the perturbation effects of a satellite to the shed material. With semi-analytical investigation and discrete element method (DEM) simulations, we reconstructed the links between the character of an already-existed satellite and the final dynamical configuration of the binary system. Special attention is also paid to binary systems whose satellite itself is a contact-binary, such as the Dinkinesh system. We propose that this kind of binary systems can only form through some specific and interesting formation paths.

This work has been supported by the National Natural Science Foundation of China grant No. 12372047.