Composite photograph of a man standing in awe of Cassiopeia A, a remnant of a once massive star that died in a violent supernova explosion three hundred twenty-five years ago. The background image was taken by three of NASA's Great Observatories, using three different wavebands of light. Infrared data from the Spitzer Space Telescope are colored red; visible data from the Hubble Space Telescope are yellow; and x-ray data from the Chandra X-ray Observatory are green and blue. Located 10,000 light years away in the northern constellation Cassiopeia, Cassiopeia A consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. The neutron star can be seen in the Chandra data as a sharp turquoise dot in the center of the shimmering shell.