In → galactic dynamics models, the process of gaining or losing → angular momentum by stars mostly at the → Lindblad resonances without gaining random motion. Figuratively, transient → spiral waves in → galactic disks churn the stars and gas in a manner that largely preserves the overall angular momentum distribution and leads to little increase in random motion. Churning is the main reason for → radial migration of stars. See also → blurring (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).
Verbal noun of → churn.