Supernova remnant
Also called: SNR.
The expanding debris of a star that exploded as a supernova.
A massive star ends its life in a supernova, an explosion briefly brighter than a whole galaxy. The blast wave sweeps up and heats the surrounding gas, which glows for tens of thousands of years.
The Crab Nebula (M 1) is the remnant of a supernova seen in 1054; the Veil Nebula in Cygnus is the delicate, lacy edge of one that exploded some 10,000–20,000 years ago.
At the eyepiece
The Veil is transformed by an OIII nebula filter: without it you may see nothing, with it the filaments look like twisted smoke.