Scientists hear 2 newborn black holes ‘crying’ through ripples in spacetime — and one had a birth unlike anything seen before SpaceGravitational wave events hint at ‘second-generation’ black holes Phys.org“What Is the Origin of the Waves?” Scientists Hunt the Source of Mysterious Ultra-Low Frequency Gravitational Signals The DebriefPerimeter researchers test the nature of merging black holes | Newswise NewswiseColliding black holes might have formed from earlier cosmic smashups Caltech