Scientists have "heard" the symphony of two newborn black holes — each created when its respective parent black holes crashed together and merged. One of those collision events, in fact, was the first of its kind.
The detection of the baby black holes and information about the four parent black holes that forged them came courtesy of ripples in spacetime, or gravitational waves, caused by the violent cosmic events that gave birth to them. Those waves were registered by the LIGO (Laser Interferometer Gravitational-Wave Observatory), Virgo, and KAGRA (Kamioka Gravitational Wave Detector) gravitational wave detectors.
