A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way. 99% of the energy released during an explosion of supernova is delivered as neutrino radiation. with matter. By the remaining percentage, the outer layers of the progenitor star strongly accelerate. The resulting supersonic shock waves from stellar material expand at a virtually constant rate of about 10,000 km/s into the interstellar medium. In this free expansion phase, which lasts about 200 years, the SNR reaches a size of about 10 light years. This is followed by about 10,000 years of continuous radiation phase.