LIGO heard the death screams when two orbiting black holes killed one or the other. Creating gravitational waves that hit headlines at top of all news that you read. The background story of that is very interesting and here http://www.newyorker.com/tech/eleme...exist-heres-how-scientists-finally-found-them Those 2 black holes are medium run of the mill black holes, one 29 and the other 36 times the mass of our sun. The resulting black hole is 62 solar mass, or energy equal to 3 suns turned into energy in fraction of a second. The 2 black holes mentioned in opening of this thread are/were (as they might well have gone BANG!) 150 million and 4 million solar mass, a huge HUGE HUGE lot bigger than 29 and 36 solar mass. THAT BANG WILL BE OUT OF THIS WORLD ENTIRELY.