The Impact of Star Parallaxes and Very Accurate Proper Motions on Galactic Structure and Dynamics Studies

Extract

Assuming that we have the absolute parallaxes and homogeneous set of proper motions for a large number of stars as described by the previous speakers - how should we use them in studies of galactic structure and dynamics?

Concerning the parallaxes I will be very brief - the subject has already been discussed by Dr. Pagel. Clearly, the main importance of the absolute parallaxes obtained is in the calibration of photometric or spectrophotometric absolute magnitude scales. For a sufficient number of stars observed in the Hyades cluster at a distance of 50 pc and in the Scorpius-Centaurus association the systematic error, which lies at the bottom of all subsequent calibration of distance indicators, may be reduced to the same order as the accuracy of photometric measurements.