Planet Detection via Microlensing

Microlensing is the most promising method to study the statistical frequency of extra-solar planets orbiting typical (random) stars in the Milky Way, even those several kiloparsecs from Earth. The lensing zone corresponds to orbital separations of a few times the Earth-Sun distance (AU) -- a good match to many planets in our own Solar System -- and the probability of detection is a rather weak function of planetary mass. Microlensing is thus a perfect complement to radial velocity and astrometric techniques that allow the detailed study of nearby planets with larger masses and smaller orbital separations. This report forms Appendix C of the Final Report of the European Southern Observatory (ESO) Working Group on the Detection of Extrasolar Planets, which contains recommendations to ESO for designing a competitive strategy in the field of extrasolar planets. The full report is available from ESO as document SPG-VLTI-97/002.