From the Astronomy Picture of the Day description:
This image combines NASA/ESA Hubble Space Telescope observations with data from the Chandra X-ray Observatory. As well as the electric-blue ram-pressure stripping streaks seen emanating from ESO 137-001, a giant gas stream can be seen extending towards the bottom of the frame, only visible in the X-ray part of the spectrum.
The electric-blue portions are made from gas and dust stripped away from the galaxy by ram pressure, which is something like wind resistance caused when a spinning bunch of stars traveling at, oh, say, 7 million kilometers per hour gets blasted by the “wind” formed from the very light gas particles that exist between galaxies. The faster galaxies whiz through the stuff, the more gas and dust gets scoured off them… and the harder it is for that galaxy to form new stars (since they’re made from gas and dust).