In a groundbreaking discovery, researchers have observed the largest collision ever recorded between two massive black holes, a finding that has prompted astrophysicists to revisit existing models of black hole formation. On November 23, 2023, scientists detected emissions from two colossal black holes, each weighing approximately 100 and 140 times the mass of the Sun. These black holes collided and merged to create a massive object estimated to be around 225 times the mass of our home star, Earth.
This monumental event presents a significant challenge to our current understanding of black hole formation. Researchers theorize that both black holes were spinning at extraordinary speeds prior to the collision, resulting in a newly formed body that defies existing theories. While Albert Einstein predicted black hole collisions over a century ago, it wasn’t until 2016 that the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States detected the first gravitational waves from such an event.
Since then, Italy has developed its own gravitational wave detector, known as Virgo, and Japan has added the Kamioka Gravitational Wave Detector (KAGRA). Together, these three observatories form the “LVK Collaboration,” which successfully identified this extraordinary cosmic event. Professor Mark Hannam from Cardiff University and a member of the LIGO Scientific Collaboration remarked, “This is the most massive black hole binary we’ve observed through gravitational waves, and it presents a real challenge to our understanding of black hole formation.”
According to current stellar evolution models, black holes of such massive scale are considered improbable. One hypothesis suggests that the two black holes in this binary may have formed through previous mergers with smaller black holes. Traditionally, scientists have theorized that a single black hole cannot exceed 100 solar masses. However, when such black holes merge, they have the potential to grow larger, leading to the formation of a single, massive body as evidenced by the recent findings.
The gravitational wave signal detected by the LVK team lasted just a tenth of a second and was approximately twenty times more powerful than most previously observed gravitational wave signals. Detectors on Earth have identified hundreds of signals indicating black hole mergers, but this particular event was exceptional. The immense rotational speed of the two black holes—spinning around 400,000 times faster than Earth—likely contributed to the remarkable strength of the gravitational wave pulse.
Gregorio Carullo of the University of Birmingham and a fellow member of the LVK noted, “It will take years for the community to fully unravel this intricate signal pattern and all its implications.” While the prevailing explanation remains that of a black hole merger, more complex scenarios may hold the key to understanding its unexpected features. With this historic discovery, the astrophysics community is poised for an exciting era of research and exploration.
