Gravitational Microlensing, The Distance Scale, And The Ages

Bohdan Paczynski

Published 1995-08-01Version 1

A high optical depth to gravitational microlensing towards the galactic bulge is consistent with current models of the galactic bar. The low optical depth towards the LMC can probably be accounted for by the ordinary stars in our galaxy and in the LMC itself. No conclusive evidence is available yet for the presence or absence of a large number of brown dwarfs or other non-stellar compact objects which might account for the dark matter. There is little doubt that the amount of mass in objects in the range 10^{-8} < M/M_sun < 10^6 will be determined within the next few years with the continuing and expanding searches. Billions of photometric measurements generated by the microlensing searches have lead to the discovery of about 10^5 variable stars. In particular, a number of detached eclipsing binaries were discovered in the galactic bulge, in the LMC, and in the globular cluster Omega Centauri. The follow-up observations of these binaries will allow the determination of accurate distances to all these objects, as well as robust age determination of globular clusters.