The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus.
It constitutes the visible portions of the Cygnus Loop, a supernova remnant, many portions of which have acquired their own individual names and catalogue identifiers.
The source supernova was a star 20 times more massive than the Sun, and it exploded between 10,000 and 20,000 years ago.
The remnants have since expanded to cover an area of the sky roughly 3 degrees in diameter (about 6 times the diameter, and 36 times the area, of the full Moon).
While previous distance estimates have ranged from 1200 to 5800 light-years, a recent determination of 2400 light-years is based on direct astrometric measurements.
