A supernova remnant is the glowing emission nebula that is left over after a supernova explosion. It is composed of the plasma that used to be part of the massive star which was blown apart. The remnant originally is pushed outward into space at a speed of up to one hundred million miles per hour. Over time, the remnant forms bright filaments of highly energized gas. Furthermore, this gas is highly enriched with heavy elements, the result of the nuclear fusion right near the end of the progenitor star’s life. These elements, such as calcium, iron, and even silver and gold, wind up being incorporated into the interstellar medium and become the raw materials for future generations of stars and planets. The Crab Nebula is a famous example of a supernova remnant.