Astronomers Detect a Black Hole Merger That's So It Shouldn't Exist

Summary

Gravitational waves—ripples in space-time caused by violent cosmic events—travel at the speed of light in every direction, eventually fading out like ripples in water. But some events are so destructive and extreme that they create disturbances in spacetime more like powerful waves than small ripples, with enough energy to reach our own detectors here on Earth. Today, the LIGO Collaboration announced the detection of the most colossal black hole merger known to date, the final product of which appears to be a gigantic black hole more than 225 times the mass of the Sun. Much about this signal, designated GW231123, contradicts known models for stellar evolution, sending physicists scrambling to apprehend how such a merger was even possible. LIGO, or the Laser Interferometer Gravitational-wave Observatory, made physics history in 2015 by detecting gravitational waves for the first time, capturing the cosmological echo of two colliding black holes. Since its Nobel-winning discovery, the LIGO Collaboration, an international partnership between LIGO and Virgo and KAGRA in Italy and Japan, respectively, has continued its meticulous surveillance of the galaxy. The collaboration has detected numerous signals from neutron stars, supernovas, and some 300 black hole mergers. The LIGO Laboratory operates two detector sites, one near Hanford in eastern Washington, and another near Livingston, Louisiana. This photo shows the Livingston detector site. Credit: Caltech/MIT/LIGO Lab But GW231123, first observed on November 23, 2023, seems to be an unprecedented beast of a black hole merger. Two enormous black holes—137 and 103 times the mass of the Sun—managed to keep it together despite their immense combined mass, spinning at 400,000 times the speed of Earth’s rotation to form an ever bigger black hole. To put its size into perspective, the previous record holder for such a merger, GW190521, is roughly 140 times the mass of the Sun. “This is the most massive black hole binary we’ve ...