These knots of gas are red because of the emission lines of hydrogen and nitrogen. They are moving at about 300 kilometers per second, a normal velocity observed in many supernova remnants. The material glows because the shock wave from the explosion has hit it, giving the atoms extra energy. The abundance of nitrogen indicates that the material came from the outer layers of the evolved star before it exploded in a process referred to as ΓÇ£mass loss.ΓÇ¥
