Kozai mechanism

In celestial mechanics, the Kozai mechanism is a dynamical phenomenon affecting the orbit of a binary system perturbed by a distant third body under certain conditions. It is also known as the von Zeipel-Kozai-Lidov, Lidov–Kozai mechanism, Kozai–Lidov mechanism, or some combination of Kozai, Lidov–Kozai, Kozai–Lidov or von Zeipel-Kozai-Lidov effect, oscillations, cycles, or resonance. This effect causes the orbit's argument of pericenter to oscillate about a constant value, which in turn leads to a periodic exchange between its eccentricity and inclination. The process occurs on timescales much longer than the orbital periods. It can drive an initially near-circular orbit to arbitrarily high eccentricity, and flip an initially moderately inclined orbit between a prograde and a retrograde motion.

The effect has been found to be an important factor shaping the orbits of irregular satellites of the planets, trans-Neptunian objects, extrasolar planets, and multiple star systems.^[1]: v It hypothetically promotes black hole mergers.^[2] It was first described in 1961 by Mikhail Lidov while analyzing the orbits of artificial and natural satellites of planets.^[3] In 1962, Yoshihide Kozai published this same result in application to the orbits of asteroids perturbed by Jupiter.^[4] The citations of the initial papers by Kozai and Lidov have risen sharply in the 21st century. As of 2017^[update], the mechanism is among the most studied astrophysical phenomena.^[1]: vi