It's well established that runaway stars and planets are a cosmic reality, but runaway galaxies? Yes, amazingly enough, those exist. Scientists have discovered at least 11 galaxies moving so quickly (up to 6 million miles per hour) that they're escaping the gravitational tug of their host clusters. Most likely, these wayward celestial bodies are the result of three-way interactions -- a small elliptical galaxy tied to a larger counterpart will fly off into space when another big galaxy gets close enough. It could take a long time before astronomers have a better sense of how common stray galaxies might be, but it's already apparent that the universe is messy at its grandest scale.
[Image credit: NASA, ESA and the Hubble Heritage Team]