Gyr-timescale destruction of high-eccentricity asteroids by spin and why 2006 HY51 has been spared

Abstract

Asteroids and other small celestial bodies have markedly prolate shapes, and the perturbative triaxial torques which are applied during pericenter passages in highly eccentric orbits trigger and sustain a state of chaotic rotation. Because the prograde spin rate around the principal axis of inertia is not bounded from above, it can accidentally reach the threshold value corresponding to rotational break-up. Previous investigations of this process were limited to integrations of $\sim 10^3$ orbits because of the stiff equation of motion. We present here a fast 1D simulation method to compute the evolution of this spin rate over $\sim 10^9$ orbits. We apply the method to the most eccentric solar system asteroid known, 2006 HY51 (with $e=0.9684$), and find that for any reasonably expected shape parameters, it can never be accelerated to break-up speed. However, primordial solar system asteroids on more eccentric orbits may have already broken up from this type of rotational fission. The method also represents a promising opportunity to investigate the long-term evolution of extremely eccentric triaxial exo-asteroids ($e>0.99$), which are thought to be common in white dwarf planetary systems

Accepted in ApJ. The computer-heavier version of chaotic rotation simulation with reparameterization is available as a Julia code at https://github.com/agoldin/2006HY51

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• Chaos over Order: Mapping 3D Rotation of Triaxial Asteroids and Minor Planets