This image is a composite that shows an optical view of the spiral galaxy NGC 1637 with an overlay of X-ray contours. The optical image shows the galaxy as a faded spiral with bright arms and a central core. The X-ray data, represented by dark grey contours, is centered on a point within one of the spiral arms, marking the location of the supernova. These contours highlight the 3 million-degree gas produced by the explosion. In late October of 1999, a supernova was detected in NGC 1637, a spiral galaxy that is 25 million light years from Earth. NASA's Chandra X-ray Observatory observed the supernova twice soon after the explosion. An X-ray source in the center of the galaxy was also detected.