NASA Astronomy Picture of the Day Collection

Lensing through Baade's Window

What is the shape and composition of our Milky Way Galaxy [ http://www.astro.wa…]? This question would be easier to answer if there wasn't so much obscuring dust [ http://antwrp.gsfc.…]! In the 1940s, however, astronomer Walter Baade [ http://yorty.sonoma…] identified a "window" near the center of our Galaxy where there is comparatively little opaque dust. Now called "Baade's Window [ http://www.as.utexa…]", this sky region contains millions of stars and is used for many studies of the distant Milky Way [ http://antwrp.gsfc.…]. 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 [ http://antwrp.gsfc.…] due to gravitational lensing [ http://www.stsci.ed…]. Current observations by the OGLE [ http://www.astro.pr…] and MACHO [ http://meteor.anu.e…] collaborations have now identified dozens of gravitational amplification events. This unexpectedly large number supports previous claims that our Galaxy [ http://antwrp.gsfc.…] has a "bar" of stars across the central nucleus, pointed nearly at the Sun [ http://antwrp.gsfc.…].

Anglo-Australian Telescope Board [ http://aaoepp.aao.g…]

Photograph made from plates taken with the UK Schmidt Telescope [ http://www.roe.ac.u…].
Color photography by David Malin.

Milky Way Galaxy

Washington

Warsaw

Goddard Space Flight Center (GSFC)

Sun

http://antwrp.gsfc.…

SPD-APOD-ap960201