Nebulae call "Veil" is the remanent of a supernova that exploded about 8,000 years ago in the constellation Cygnus. The eastern veil is located about 1,400 light year form Earth and its visual magnitude is 7. A supernova is a stellar explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy. Supernovae can be triggered in one of two ways: by the sudden reignition of nuclear fusion in a degenerate star; or by the collapse of the core of a massive star.