What is a Supernova Remnant?
As the title suggests, a supernova remnant is the remains of a supernova, a stellar explosion. An event caused by one of two ways, either a massive star's core suddenly collapses after running out of enough fuel to generate fusion energy, or when a white dwarf star accumulates too much matter from a star it's in orbit with, becoming unstable and exploding. What are left after these spectacular phenomena are supernova remnants, highly luminous structures expanding their stellar guts at as much as ten percent the speed of light, replenishing the interstellar medium and carrying with them elements such as carbon, nitrogen, and oxygen among other ingredients responsible for life itself.