A collision between two massive black holes creates a body that rotates at dizzying speeds and contradicts standard models – possibly resulting from previous mergers
A record-breaking collision between black holes has stunned scientists with its size and speed.
The LIGO-Virgo-KAGRA (LVK) collaboration has made a groundbreaking discovery: the most massive black hole merger ever recorded using gravitational waves. The black hole created in the merger is more than 225 times as massive as our Sun. The signal, designated GW231123, was detected by the fourth LVK network observatory on November 23, 2023.
The estimated masses of the two merging black holes were about 100 and 140 solar masses. In addition to their unusual size, they were spinning at extreme speeds. This combination made the signal particularly difficult to analyze and suggests that these black holes may have had an unusually complex origin story.
The mystery of formation beyond the standard models
"This is the most massive black hole pair ever observed using gravitational waves, and it is a real challenge to our understanding of how black holes form," says Professor Mark Hannam of LIGO. "Black holes of this mass are forbidden by standard models of stellar evolution. One possibility is that the two black holes in this pair were formed through previous mergers of smaller black holes."
Scientists have observed about 300 black hole mergers using gravitational waves to date, including new candidates from the current observing system. Before GW231123, the largest verified black hole pair was associated with the event GW190521, whose total mass was significantly smaller, "only" 140 solar masses.
Pushing the boundaries of discovery
The large mass and extremely fast rotation of the black holes in GW231123 are pushing the limits of gravitational wave detection technology and current theoretical models. Extracting precise information from the signal required the use of theoretical models that take into account the complex dynamics of extremely fast-spinning black holes.
"The black hole appears to be spinning very fast – close to the limit allowed by Einstein's general theory of relativity," explains Dr. Charlie Hoy. "So it's difficult to model and interpret the signal. This is an excellent case study to advance the development of our theoretical models."
Scientists continue to refine their analysis and improve the models used to interpret such extreme events. “It will take the community years to fully understand this complex signal pattern and all its implications,” says Dr. Gregorio Cruyo. “While the most likely explanation is still a merger of black holes, more complex scenarios could hold the key to deciphering these unexpected features. Exciting times lie ahead!”
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