Stellar Kinematics and the Dynamical Evolution of the Disc

Stars form within clusters and associations, which gradually dissipate through gravitational interactions, dispersing the component stars throughout the Milky Way. The prime aim of stellar kinematics is to describe the current motions of stars and use those statistical quantities to probe their dynamical history. This chapter describes its origins in Jacobus Kapteyn’s systematic analyses of photographic plates taken at the Cape Observatory run by David Gill and provides a summary of our current knowledge of the kinematics of local stars, notably results generated by the Hipparcos astrometric mission. We discuss the evidence for ‘star streams’ and whether these kinematic groupings reflect residual components of individual stellar clusters, or whether they are generated by dynamical resonances generated by large-scale features such as the Bar. We consider the potential for stellar migration and radial mixing within the Milky Ways disc.