: In this handout photo provided by the National Science Foundation, the Event Horizon Telescope captures a black hole at the center of galaxy M87, outlined by emission from hot gas swirling around it under the influence of strong gravity near its ev Star collapses couldn't create stellar black holes much bigger than 70 times the mass of our sun, scientists thought, according to physicist Nelson Christensen, research director of the French National Centre for Scientific Research.AdvertisementThen in May 2019 two detectors picked up a signal that turned out to be the energy from two stellar black holes — each large for a stellar black hole — crashing into each other.