A supernova remnant is the structure resulting from the explosion of a star in a supernova event. When a massive star exhausts its nuclear fuel, it can no longer support itself against gravitational collapse, leading to a violent explosion. This explosion disperses the star's outer layers into space, creating a cloud of gas and dust. These remnants can be observed in various wavelengths, including radio, optical, and X-ray. They often contain elements like hydrogen, helium, and heavier elements formed during the star's life. Supernova remnants play a crucial role in enriching the interstellar medium, contributing to the formation of new stars and planets.