A New Equilibrium State for Singly Synchronous Binary Asteroids

Oleksiy Golubov1,2,3, Vladyslav Unukovych2, and Daniel J. Scheeres1
Astrophysical Journal Letters 857, L5 Link to Article [DOI: 10.3847/2041-8213/aaba15]
1Department of Aerospace Engineering Sciences, University of Colorado at Boulder, 429 UCB, Boulder, CO 80309, USA
2School of Physics and Technology, V. N. Karazin Kharkiv National University, 4 Svobody Square, Kharkiv, 61022, Ukraine
3Institute of Astronomy of V. N. Karazin Kharkiv National University, 35 Sumska Street, Kharkiv, 61022, Ukraine

The evolution of rotation states of small asteroids is governed by the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, nonetheless some asteroids can stop their YORP evolution by attaining a stable equilibrium. The same is true for binary asteroids subjected to the binary YORP (BYORP) effect. Here we discuss a new type of equilibrium that combines these two, which is possible in a singly synchronous binary system. This equilibrium occurs when the normal YORP, the tangential YORP, and the BYORP compensate each other, and tidal torques distribute the angular momentum between the components of the system and dissipate energy. If unperturbed, such a system would remain singly synchronous in perpetuity with constant spin and orbit rates, as the tidal torques dissipate the incoming energy from impinging sunlight at the same rate. The probability of the existence of this kind of equilibrium in a binary system is found to be on the order of a few percent.


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