Chandra Release - April 19, 2005

Visual Description: G21.5-0.9

The X-ray image of the supernova remnant G21.5-0.9 displays a bright, greyish-white circular object in the center of larger, dark teal gaseous material, also in a circular shape, situated on a black background.  The circular object in the center of the image resembles a lens with intricate, swirling patterns visible throughout its surface.  The edges of the larger circular object appear hazy and diffuse. This image, made by combining 150 hours of archived Chandra data, shows the remnant of a supernova explosion. The central bright cloud of high-energy electrons is surrounded by a distinctive shell of hot gas.  The shell is due to a shock wave generated as the material ejected by the supernova plows into interstellar matter. The shock wave heats gas to millions of degrees, producing X-rays in the process. Although many supernovas leave behind bright shells, others do not. This supernova remnant, identified as G21.5-0.9 by radio astronomers 30 years ago, was considered to be one that had no shell until it was revealed by Chandra.