Stephan's Quintet is the cosmic equivalent of glass and metal scattered across a road after a car crash. The four galaxies involved have already hit each other and sent some of their material flying into a debris field, and are slowly skidding back together where they'll probably merge into one giant galaxy eventually. "Slowly" is, of course, a relative term: these galaxies are traveling at millions of miles per hour, but because it's happening on the cosmic scale it will still take a few million years before they merge. In our tiny human experience, we basically see a freeze frame of the whole event.