"This was the start of my interest in stellar kinematics," he said, according to information in his curriculum vitae.

Within the Milky Way galaxy, there are three primary components of stellar kinematics: the disk, halo and bulge or bar.

Whilst critical for an understanding of stellar kinematics, and hence population dynamics, its effect is generally imperceptible to astrometric measurements (in the plane of the sky), and therefore it is generally ignored in large-scale astrometric surveys.