Lensing through Baade's Window

Explanation: What is the shape and composition of our Milky Way Galaxy ? This question would be easier to answer if there wasn't so much obscuring dust ! In the 1940s, however, astronomer Walter Baade identified a “window” near the center of our Galaxy where there is comparatively little opaque dust. Now called “ Baade's Window ”, this sky region contains millions of stars and is used for many studies of the distant Milky Way . One clever use, devised by Bohdan Paczynski, is to monitor millions of stars in our Galactic Bulge - many through Baade's window - for sudden brightening due to gravitational lensing . Current observations by the OGLE and MACHO collaborations have now identified dozens of gravitational amplification events. This unexpectedly large number supports previous claims that our Galaxy has a “bar” of stars across the central nucleus, pointed nearly at the Sun .