Scientists Discover Forbidden Zone Where Black Holes Cannot Form

A Gap in the Cosmos

An international team of astrophysicists, led by Monash University PhD candidate Hui Tong, has uncovered the strongest evidence yet for a so-called forbidden mass range in the universe, a zone where stellar-origin black holes simply cannot exist.

The study, published in Nature in April twenty twenty six, analysed data from the fourth Gravitational-Wave Transient Catalogue, compiled by the LIGO, Virgo, and KAGRA observatory network. By examining the masses of black holes detected through gravitational wave signals, the researchers identified a clear gap between roughly forty four and one hundred and sixteen solar masses among secondary black holes in merging binary systems.

Why the Gap Exists

The explanation lies in a dramatic stellar phenomenon known as pair-instability supernovae. When the most massive stars reach the end of their lives, temperatures in their cores become so extreme that photons begin spontaneously converting into pairs of electrons and positrons. This process robs the star of the radiation pressure keeping it from collapsing. Gravity briefly overwhelms the star, compressing its core until thermonuclear reactions ignite an explosion so powerful that the entire star is obliterated, leaving no remnant behind, not even a black hole.

This means stars that would theoretically produce black holes in this mass range instead destroy themselves completely.

Mergers Fill the Gap

Intriguingly, a small number of black holes have been detected within this forbidden range. The leading explanation is that these objects formed not from individual stellar collapse, but from the mergers of smaller black holes that gradually combined to reach masses that would otherwise be impossible to achieve in a single step.

A New Window on Stellar Death

The discovery demonstrates the extraordinary power of gravitational wave astronomy. By studying ripples in spacetime, scientists can now reconstruct the outcomes of stellar explosions indirectly, through the population of black holes they leave behind, opening entirely new pathways for understanding how the most massive stars in the universe live and die.