For generations, astronomers imagined the death of a galaxy as a violent collision — two worlds meeting, a black hole erupting, stars ceasing to be born. Now, a careful analysis of more than eleven thousand simulated galaxies suggests the true story is quieter and more relentless: it is the slow, sustained breath of a massive black hole, not the drama of cosmic collision, that most often extinguishes a galaxy's light. Researchers at Florida International University, working with one of the most sophisticated galaxy simulations ever constructed, found that mergers account for only a sliver of s