There is striking evidence that two galaxy subclusters have recently collided in Abell 754.
White lines show the distribution of hot, X-ray emitting gas.
In a cosmically short time, probably in a few billion years, our Milky Way galaxy will smash into the Andromeda galaxy. Pulled together by gravity, the two spiral galaxies will violently merge perhaps into another kind of galaxy, an elliptical galaxy. When the Andromeda and Milky Way collide, their respective dwarf satellite populations may become a single large satellite population around the merged central galaxy. Astronomers really don't know if the environment in our galactic neighborhood typifies the environment of other groups of galaxies. But it is a basic and compelling question, because if our local neighborhood environment is common in the universe, then this may be the type of environment where most galaxies evolve, says Ann Zabludoff.