Chandra Release - January 10, 2007

Visual Description: Light Echo at Galactic Center

 The four-image set features a supermassive black hole named Sagittarius A* (pronounced "A-star") in the Milky Way galaxy.  The images are dominated by shades of blue.  Sagittarius A* is depicted as a bright white-blue spot in the center of the image, surrounded by bright blue blobs and dots.   This set of Chandra images shows evidence for a light echo generated by Sagittarius A*. Astronomers believe a mass equivalent to the planet Mercury was devoured by the black hole about 50 years earlier, causing an X-ray outburst which then reflected off gas clouds near Sagittarius A*. The large main image on the right shows a Chandra view of the middle of the Milky Way, with Sagittarius A* labeled. The 3 smaller images on the left show close-ups of the region marked with ellipses. Clear changes in the shapes and brightness of the gas clouds are seen between the 3 different observations in 2002, 2004 and 2005. This behavior agrees with theoretical predictions for a light echo produced by Sagittarius A*.