New Study Finds Evidence of Cosmic Explosions with Missing Black Holes

CITA researchers Maya Fishbach, Amanda Farah and Aditya Vijaykumar are part of an international team that has uncovered evidence of a rare form of exploding star, shedding light on one of the most cataclysmic events in the Universe. Their study, published in Nature today, confirms that black holes with masses larger than 45 times the mass of the sun are the result of previous black hole mergers, rather than the collapse of enormous dying stars.

Using data from the LIGO-Virgo-KAGRA observatory network, the international team led by Hui Tong, a PhD candidate from Monash University’s School of Physics and Astronomy and the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), was able to measure the properties of black holes in the “forbidden range” (of over 45 times the mass of the sun) and confirm the theoretical prediction of ‘pair-instability supernovae’.

This artist’s impression shows a stellar explosion with subtle hints of a black hole binary in the background, released on April 1, 2026. Credit: Carl Knox, OzGrav–Swinburne University of Technology

Why are black holes heavier than 45 solar masses so rare? At the end of their lives, most massive stars collapse into black holes – objects with gravity so strong that not even light can escape. Presumably, the universe’s most massive stars should collapse to form the most massive black holes. However, some very massive stars become so hot that they are blown apart in a pair-instability supernova – an explosion so intense that it destroys the star, leaving no core behind that can collapse into a black hole.

Project lead, Hui Tong, explained that the team’s analysis of gravitational wave signals – the ripples in the fabric of spacetime – detected by the LIGO-Virgo-KAGRA observatory afforded evidence of the existence of the forbidden mass range where stars seemingly don’t make black holes.

“The observation is well explained by pair instability; there are no stellar-origin black holes in the forbidden zone because stars are undergoing pair-instability supernovae. The only black holes in this mass range are made from merging smaller black holes, rather than directly from stars,” Mr. Tong said.

Confirming the existence of this gap would help settle a major question about how the most massive stars live and die, and the origin of black holes.

Project collaborator, Professor Maya Fishbach from the University of Toronto and CITA said the study highlights the potential of gravitational waves to probe the lives, deaths and afterlives of the most massive stars in our Universe.

“We are seeing indirect evidence of one of the most titanic blasts in the cosmos: pair-instability supernovae. At the same time, we are finding that once they are born, black holes can grow via repeated mergers,” said Professor Maya Fishbach.

First predicted in the 1960s, pair-instability supernovae are challenging to distinguish from more common stellar explosions that leave behind black holes. Coauthor Amanda Farah, who is a CITA postdoctoral fellow, commented: “We rarely (if ever) get to see these types of explosions in real-time, so it’s amazing that we can observe their lasting imprints so clearly in the gravitational-wave data. These imprints — the black holes that pair-instability supernovae fail to leave behind — are already teaching us about nuclear physics. This was one of the early promises of gravitational-wave astronomy, and it’s so exciting to see that promise fulfilled today.”

Another CITA postdoctoral fellow, coauthor Aditya Vijaykumar, expects that these new findings are an important step forward in gravitational wave research: “The impact of this work is already being felt across the community. It has already sparked a wave of follow-up research, and there are now multiple lines of evidence suggesting that some black hole mergers involve components born in earlier collisions. Such black hole mergers are thought to be produced in regions of the Universe that host a dense crowd of stars, and I am excited for all that we will learn about these environments in the future. It is a fascinating time for our field!”

Nature paper, “Evidence of the pair-instability gap from black-hole masses”, https://doi.org/10.1038/s41586-026-10359-0

New Study Finds Evidence of Cosmic Explosions with Missing Black Holes

NEWS