This image is a combination between an X-ray image from the Chandra X-ray observatory, and a visible spectrum image from the ESO's Very Large Telescope in Chile. That purple splotch is a giant cloud of superheated (six million degree) gas that's only visible in X-rays. Astronomers think that it's the remains of a collision between the big spiral galaxy in the background and a much smaller dwarf galaxy. That bright X-ray dot on the lower right is a region of active star formation, possibly caused by the shockwave from the collision itself.
Via Chandra