An Etymological Dictionary of Astronomy and Astrophysics

The progressive increase of random motions of → disk stars with increasing stellar → ages. While some initial random
motion seems likely in the disturbed conditions of disks
when the oldest stars formed, the observation is generally attributed to scattering processes. Both massive gas → clumps and → spiral waves are considered as scattering agents (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).

See also: → scattering; → star.