Globular clusters are among the oldest components of our galaxy.
For various reasons, measurements of the globular cluster distances suffer from systematic errors and remain the limiting factor in determining the ages of these objects. Ian Thompson, with colleagues at the Observatories and the University of Warsaw, has a different approach to this distance problem. Observations of detached eclipsing binary stars allow a geometric measurement of distances. These systems are composed of two separated stars that orbit about each other, with the orbital plane in the line of sight to the stars. As one star passes in front of the other, the total light is modulated.