Labels:text | screenshot | map OCR: SUPERNOVA REMNANTS WHEN A STAR explodes as a supernova, its outer layers of gas are shed to form a glowing supernova remnant, speeding away from its core. Some explosions are so violent that the core is also destroyed. About 90 percent of remnants are roughly spherical. The remainder is broken up by the force of the explosion to form a mass of gaseous filaments with no apparent structure. Pulsars have been detected at the center of such remnants. THE CYGNUS LOOP This image of a supernova remnant EXPLOSIVE shows interstellar gas that has been WAVES heated by the supernova shock wave.