Veil Nebula

The Veil Nebula is the remnant of a massive star that exploded as a supernova approximately 10,000–20,000 years ago. The progenitor star was around 20 times the mass of the Sun. The full Cygnus Loop complex spans roughly 3 degrees of sky — about six full Moon diameters — though only sections are typically shown in deep-sky images.

NGC 6992 is the brightest arc of the Eastern Veil; the Hubble image shown here captures a small section revealing the nebula’s extraordinary filamentary structure in exceptional detail. The wisps and threads of ionized gas represent a thin sheet of the expanding shock wave seen nearly edge-on from Earth.

The colors encode different physical processes: oxygen emission (shown in blue-green) traces the hot, compressed gas at the shock front; hydrogen emission (shown in red) marks regions where the shock has swept up and heated surrounding interstellar material; sulfur emission (shown in deep red) indicates areas of partially ionized, cooler gas behind the shock.

The shock wave is expanding at roughly 170 km/s, a speed that will gradually slow as it sweeps up more interstellar material over the coming millennia.