Published online by Cambridge University Press: 06 January 2010
Ground-based optical interferometers can perform astrometric measurements with a precision approaching 10μas between pairs of stars separated by ~10″ on the sky. These narrow-angle measurements can be used to search for extrasolar planets and to determine their orbital parameters, to characterize microlensing events, and to measure the orbits of stars around the black hole at the center of our Galaxy.