Supernova remnant some 800 light years from Sol. This nebula is the remnant of a supernova that exploded about 10,000 years B.T. The Vela Supernova Remnant is near the centre of a much older nebula, the Gum Nebula (Gum 12) which is itself the remnant of a supernova.
Supernova Remnant - Text by M. Alan Kazlev The expanding and cooling shell of gas and dust that is visible for thousands of years after a supernova. After a few tens of thousands of years supernova remnants mix with the interstellar medium and dissipate.