NGC6990 - Western Veil Nebula
Discovered by William Herschel in 1784, the Veil is a remnant of a colossal supernova explosion that occurred approximately 5,000 - 8,000 years ago leaving delicate wisps of gas in a roughly spherical pattern in the constellation Cygnus. The filamentous nature of the gas patterns is attributed to the ultra-thin shockwaves of the explosion, which result in a visible shell only when viewed precisely edge-on. The western arm of the nebula shown in this image exemplifies the red hydrogen and blue oxygen lace work typical of these remnants. The prominent star dominating the image, 52 Cygni, is actually in the foreground.