Veil nebula supernova remnant, NGC 6979. Optical image of a region of the Veil nebula, part of the Cygnus Loop, which is the remnant of a supernova that exploded some 5-8000 years ago. The gas ejected from the explosion expands outwards, colliding with interstellar material at high speed. The shock of the impact ionises the gases, causing them to glow. The roughly circular Cygnus loop describes the outer shell of these expanding gases. The nebula lies about 1400 light years away in the constellation Cygnus.