orbital resonance(redirected from Mean-motion resonance)
orbital resonanceAn effect in celestial mechanics that arises when two orbiting bodies have periods of revolution that are in a simple integer ratio allowing each body to have a regularly recurring gravitational influence on the other. Orbital resonance may stabilize the orbits and protect them from perturbation, as in the case of the Trojan group of asteroids, which are held in place by a 1:1 resonance with Jupiter. On the other hand, orbital resonance may destabilize one of the orbits, ejecting the body concerned, changing the eccentricity of its path, or sending it into a different orbit. This second effect of orbital resonance accounts for why there are virtually no asteroids in certain regions of the main asteroid belt (see Kirkwood gaps). Laplace resonance is a form of orbital resonance that occurs when three or more orbiting objects have a simple integer ratio between their orbital periods. For example, the Jovian satellites Io, Europa, and Ganymede have periods of revolution in the ratio 4:2:1.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006