Veil nebula. Optical image of part of the Veil nebula (Cirrus Nebula, NGC 6992-6995). This is the easternmost and brightest part of the Cygnus Loop supernova remnant that lies about 2600 light years from Earth in the constellation Cygnus. The loop's shell of gas, which is expanding at about 100 kilometres per second, was produced from an exploding star tens of thousands of years ago. As the gas collides with the surrounding matter, the shock wave ionises the gas atoms, producing light. This image was produced using the Canada- France-Hawaii Telescope, Mauna Kea, Hawaii, USA.