Astronomy Colloquium / Spring 2009

February 20

Prof. Andy Gould

Institut d'Astrophysique de Paris and Ohio State University

"Microlensing: Measuring the Galactic Distribution of Planets"

Microlensing has discovered 13 planets, including the first "cold Neptunes", the first Sun/Jupiter/Saturn analog, the least massive planet, and the heaviest planet orbiting an M dwarf. A great strength of microlensing is that it does not depend on photons from the host star, and so probes classes of planets not accessible to other techniques. Originally, this was also considered a great weakness: since the host cannot be seen, we generally did not be expect to be able to determine its mass and distance. I show that masses and distances have nevertheless been measured for the majority of planets discovered to date. In particular, we can determine which are in the Galactic disk vs the Galactic bulge. I report a very surprising initial result from this observed distribution of distances.