Relaxation time

Relaxation time is a characteristic time relating to clusters of gravitationally-interacting bodies (star clusters, galaxy clusters, globular clusters). Various events occur on timescales relating to the relaxation time, including:

• Core collapse
• Energy exchange between stars (minimization of the total energy in a cluster)

Physical interpretation

The relaxation time is related to the velocity of a body (typically a star) and the perturbation rate. In the example of a star cluster, a particular star will have an orbit with a velocity v. As the star passes by other stars, the orbit will be perturbed by the gravitational field of nearby stars. The relaxation time is similar to the ratio of the velocity to the time derivative of the perturbation.