New research has revealed the true origins of the universe’s largest black holes, addressing one of the most important missing link problems in modern astrophysics.
New analysis of gravitational waves suggests that, unlike other types of black holes, the most massive ones do not form from stellar collapses, but rather from hierarchical mergers within tightly packed star clusters.
The Cardiff University researchers studied 153 detections from the LIGO-Virgo-KAGRA catalog and identified two different populations of black holes.
According to findings published in Nature Astronomythe lower mass black holes exhibit slow rotations and are formed by the traditional collapse of stars.
On the other hand, higher masses, which could be “second generation” black holes, spin rapidly and are created by successive collisions in a crowded environment.
“Gravitational wave astronomy is beginning to reveal how black holes grow, where they grow, and what that tells us about the life and death of massive stars,” said lead author Dr. Fabio Antonini from Cardiff University’s School of Physics and Astronomy.
“What surprised us most was how clearly the high-mass black holes stand out as a distinct population,” says co-author Dr. Isobel Romero-Shaw.
Evidence for mysterious ‘mass divide’
Astrophysicists have long predicted a mass gap in pair instability starting around 45 solar masses.
According to this theory, when stars of a certain size explode so violently, they leave nothing behind. It means that black holes should not exist in this particular mass range.
Antonini said: “The largest black holes in the current sample seem to tell us about cluster dynamics, and not just about stellar evolution.”
Therefore, research suggests that the large black holes in this ‘forbidden’ area are not ‘born’ there, but ‘grow’ in it through mergers.
New window into nuclear physics
“In the future, gravitational wave data could help scientists study nuclear physics, because the mass limit set by the instability of pairs depends on the nuclear reactions taking place in the cores of massive stars,” added co-author Dr. Fani Dosopoulou, a research fellow at Cardiff University, added.
