Turning Companions into Planets - HST Astrometry of Extrasolar Planet Candidates

Fritz Benedict

In the last ten years we have witnessed the birth of a new branch of astronomy; the study of planets orbiting other stars. 98% of these objects were found by discovering variations in radial velocity. However, the radial velocity technique only provides a minimum mass, not a true companion mass. Does it matter? Yes! Aside from distance from the host star, the mass of a planet most determines what kind of place it is; gas giant or terrestrial.. Astrometry rides to the rescue, and produces true masses. This talk shows you how, and outlines the bright future of extrasolar planet astrometry.