Microlensing Planet S earch Project
Planetary systems in the foreground of the Galactic Bulge form a class of (planetary) binary lens systems that can be detected through photometric microlensing experiments. An Earth mass planet orbiting a lensing star can perturb the would-be single lens microlensing light curve due to the lensing star, briefly but spectacularly. Gravitational microlensing is the only known ground-based method to probe earth mass planets orbiting around main sequence stars. (Earth mass objects orbiting a neutron star were discovered in 1992 by Wolszczan and Frail.)
The Galactic Bulge (Dec: -30°) can be best observed from Southern Hemisphere observatories in South America, Australia, and South Africa (Lat: -30°) or even in Antarctica. Planetary binary lensing is rare and the planetary signals are fairly brief -- with the lower mass planets generating rarer and the shorter planetary signals. Thus, "microlensing planet patroling" requires continuous coverage of microlensing alert events, and the three continents are more or less optimally distributed for this purpose. The South Pole offers the possibility of continuous monitoring during the Southern winter (when weather permits). (The top of this map has the same longitude as this web server, 273.8°.)

The Microlensing Planet Search Project (MPS) searches for evidence of extra-solar planets using the gravitational microlensing technique. Photometric microlensing is capable of probing the entire mass range of planets from Super-Jupiter mass to Earth mass. The figure above shows an example of a microlensing lightcurve which shows evidence for an Earth mass planet as a brief deviation in the lightcurve. The universality of gravity gurantees that gravitational microlensing is also sensitive to unbound planets ("rogue planets") or brown dwarfs. (One conventional thought is that planets are formed through accretion and brown dwarfs are formed through fragmentation during star formation. Abundant statistics of microlensing planets can provide an important clue to test this scenario.)

MPS is affiliated with the  Global Microlensing Alert Network (GMAN) which operates in cooperation with the  MACHO microlensing survey project. MPS observes microlensing events in progress from the 1.9m telescope at the  Mount Stromlo Observatory in Australia and plans to observe from the 1.5m telescope at the  Boyden Observatory in South Africa beginning in the 1999 Galactic bulge season. At present, MPS involves  collaborators  from the University of Notre Dame, the University of Washington, and the Mount Stromlo Observatory.

MPS relies upon microlensing alerts from:

Microlensing Events

The following is a list of current and recent microlensing events that have shown interesting deviations from standard microlensing which have been observed or analyzed by the MPS group.

MPS Related Papers

The following is MPS related work by collaboration members. Some of it is theoretical: