orbital resonance

(redirected from Mean-motion resonance)

orbital resonance

An 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.
References in periodicals archive ?
The team's analysis of the system's long-term behavior indicates that the system will be unstable unless the objects are locked in a 1:5 mean-motion resonance (January issue, page 44).
Peale (both at the University of California, Santa Barbara)--show that the planets are tightly locked in this 2:1 mean-motion resonance, which is stable for billions of years.
The two known planets orbiting the Sun-like star HD 82943 in Hydra are also locked in a 2:1 mean-motion resonance. But computer simulations indicate that HD 82943's resonance is not as tight as Gliese 876's, and the orbits are considerably more eccentric.
The Neptune/Pluto and Jovian-moon relationships are known as mean-motion resonances. Two or more bodies in this type of resonance have orbital periods whose long-term averages can be expressed as a ratio of integers.