The heaviest black hole merger, GW231123, detected by the LIGO-Virgo-KAGRA collaboration, falls into the 'mass gap' (the range where ordinary stars can't form black holes) and has unusually high spins (rotation speeds). A new study suggests that both black holes could be primordial — born in the first moments after the Big Bang — and later grew their mass through accretion, naturally explaining the observed parameters. Remarkably, the model parameters sit right at the edge of regions ruled out by X-ray and microwave observations, making the hypothesis testable. The upcoming O5 observing run should detect about 20 similar events, allowing scientists to test the predicted mass-spin relationship.
Detectors of gravitational waves caught the merger of two unusually heavy black holes — event GW231123. Their mass is too large to come from ordinary stars. Scientists believe they grew from tiny seeds that appeared right after the Big Bang. This idea of primordial black holes was proposed by Stephen Hawking.
The growth of such a hole is like a whirlpool in a sink: the more matter it sucks in, the more massive it becomes and the faster it spins. Over billions of years, dust and gas spun it up to enormous speeds, explaining both the mass and spin of GW231123.
🎯 Primordial black holes could have formed from random clumps of energy in the first second after the Big Bang.
🎬 In science fiction, tiny primordial black holes are sometimes depicted as invisible 'bullets' that can pass through planets and cause disasters.