20,000 years ago there was a supernova explosion in the constellation of Cygnus. Its shockwave is still expanding into interstellar space. The impact of the fast moving wall of gas on a stationary cloud has heated it causing it to glow with visible light as well as high energy radiation. The result is the nebula known as the Cygnus Loop (NGC 6960/95). The colors in this Hubble Space Telescope image indicate emission from different kinds of atoms excited by the shock: oxygen-blue, sulfur-red, and hydrogen-green.
There’s a picture of the Cygnus Loop in UV here.
Image Credit: NASA / ESA