Giant black holes are cosmic ‘Frankensteins’ built by mergers, new study reveals

A new research has revealed the true origin of the Universe’s biggest black holes, addressing one of the most significant missing link problems in modern astrophysics.

New analysis of gravitational waves suggest that unlike other types of black holes, the most massive ones are not born from stellar collapse, but rather through hierarchical mergers inside densely packed star clusters.

The researchers from Cardiff University studied 153 detections from the LIGO-Virgo-KAGRA catalog and identified two different populations of black holes.

According to findings published in Nature Astronomy, the lower mass black holes show slow spins and are formed by the traditional collapse of stars.

On the other hand, higher-mass which could be “second-generation” black holes spin rapidly and are created by successive collisions in a crowded environment.

"Gravitational-wave astronomy is starting to reveal how black holes grow, where they grow, and what that tells us about the lives and deaths of massive stars,” lead author Dr. Fabio Antonini from Cardiff University's School of Physics and Astronomy said.

"What surprised us most was how clearly the high-mass black holes stand out as a separate population," said co-author Dr. Isobel Romero-Shaw.

Evidence for mysterious ‘mass gap’

Astrophysicists have long predicted a pair-instability mass gap starting around 45 solar masses.

As per this theory, when stars of a certain size explodes so violently they leave nothing behind. It means that black holes must not exist in this specific mass range.

Antonini said, "The biggest black holes in the current sample seem to be telling us about cluster dynamics, not just stellar evolution.”

Hence study suggests the large black holes found in this "forbidden" range are not "born" there, but "grow" into it through mergers.

New window in nuclear physics

"In the future, gravitational-wave data may help scientists study nuclear physics, because the mass limit set by pair instability depends on the nuclear reactions taking place in the cores of massive stars," added co-author Dr. Fani Dosopoulou, a research associate at Cardiff University.