The Veil Nebula is a sprawling supernova remnant in the constellation Cygnus and is one of the most intricate and beautiful objects visible with a small telescope. The nebula was formed by two stars that exploded 18,000 and 5,000 years ago, approximately. The stars were just 2,000 light years away, close enough to create a spectacular display when they detonated. Each must have shone as bright as a crescent Moon and cast shadows by night for weeks, but there are no records of these prehistoric events carved on a cave wall anywhere, at least none yet discovered.
The Veil is segmented into several sections. The eastern section of the nebula, shown above in this fine image by Jeff Johnson, is made of sections cataloged as NGC 6992 and smaller NGC 6995. NGC 6992 is the brightest and easiest to see. You can spot it in 7×50 binoculars if you have extremely dark sky. The fainter western section of the nebula is cataloged as NGC 6960. Though harder to see, this section is set against the lovely 4th-magnitude foreground star 52 Cygni.
If you haven’t glimpsed the Veil Nebula for yourself, both main sections are visible in a 4″ small telescope in dark sky. A UHC or OIII nebula filter is a big help to see this nebula, especially if any light pollution is present. Even with a low power eyepiece, you’ll only see one section at a time. It’s a big complex. The entire nebula spans as much sky as seven full moons.
(I once had the pleasure of seeing the Veil, bit by bit, through a 25″ Dobsonian telescope under nearly perfect sky. It was so beautiful, I nearly fell off the ladder when looking through the eyepiece).
The bright optical filaments in the Veil Nebula are caused by the supernova blast wave colliding with interstellar clouds. As the shock wave slows down, it loses energy by emitting visible light.