2020ApJ...899..103M

Asteroids and other small celestial bodies have markedly prolate shapes, and the perturbative triaxial torques that 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 breakup. Previous investigations of this process were limited to integrations of ∼10³ 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 ∼10⁹ 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 breakup 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.