This ultraviolet light image allows us to view the full scope of the Veil Nebula. Cast off by a supernova explosion, the Veil Nebula is now a bubble of gas expanding rapidly.
    To radiate in the ultraviolet region of the spectrum, gas must reach a temperature of several million degrees, so the gas in this image must be extremely hot. Yet the Veil Nebula is far too old for the heat to be left over from the original supernova explosion. Rather, the fast-moving shell is heated from the “shock” of its slamming into the surrounding stationary gas. 
    This image was generated by the Extreme Ultraviolet Explorer (EUVE). Because ultraviolet light is largely blocked by the ozone layer