Supermassive black holes, such as this one in NGC 5195, occupy the centres of most galaxiesX-ray: NASA/CXC/Univ of Texas/E.Schlegel et al; Optical: NASA/STScIIt’s a self-inflicted wound of cosmic proportions. When two galaxies go to war, they fling many of their own stars into the supermassive black holes at their centres, gobbling them up for good....