Astronomers have detected an anomalous merger of black holes

An international team of astronomers has detected an unusual cosmic event: the merger of two black holes that was likely accompanied by a burst of X-ray and gamma-ray radiation. The study has been published in The Astrophysical Journal Letters (AJL).

First, on November 25, 2024, the LIGO–Virgo–KAGRA gravitational wave detectors registered a signal from the collision of two black holes at a distance of about 4.2 billion light-years from Earth. The resulting object had a mass approximately 150 times that of the Sun.

However, roughly 11 seconds later, telescopes detected a burst of X-ray and gamma-ray radiation from the same region of the sky. Scientists estimated the probability of a random coincidence as extremely low — approximately one occurrence per several decades of observations.

Typically, black hole mergers are considered "dark" events: they do not emit light, since all processes are hidden behind the event horizon. Therefore, the detection of a possible light signal came as a surprise.

A team led by astronomer Shu-Rui Zhang from the University of Science and Technology of China proposed an explanation: the collision may have occurred inside the accretion disk of a supermassive black hole — in an active galactic nucleus.

In such regions, space is filled with hot gas and dust. If two black holes merge in such an environment, the resulting object can receive a "kick" and begin moving through the dense matter. This triggers intense accretion of material and the formation of jets, which produce the bright radiation.

Modeling showed that this scenario is capable of explaining the characteristics of the observed gamma-ray burst, which differs from typical flares that arise from supernova explosions or neutron star mergers.

The authors emphasize that their hypothesis requires further verification. In particular, it is necessary to refine the orbital parameters of the merging objects and conduct deeper observations of the source galaxy.