  Accuracies reached in space astrometry now permit the accurate determination
of astrometric radial velocities, without any use of spectroscopy. Knowing this
true stellar motion, spectral shifts intrinsic to stellar atmospheres can be
identified, for instance gravitational redshifts and those caused by velocity
fields on stellar surfaces. The astrometric accuracy is independent of any
spectral complexity, such as the smeared-out line profiles of rapidly rotating
stars. Besides a better determination of stellar velocities, this permits more
precise studies of atmospheric dynamics, such as possible modifications of
stellar surface convection (granulation) by rotation-induced forces, as well as
a potential for observing meridional flows across stellar surfaces.
