An international team of astronomers, co-led by a scholar from the Institute for Advanced Study (IAS), has identified what appears to be a universal physical rule governing one of the most dramatic and energetic behaviors observed in black holes: the production of powerful radio jets.
The researchers discovered that black holes are capable of launching these intense streams of matter at the exact same critical stage of their feeding cycle, regardless of their scale. This remarkable consistency applies across a vast cosmic spectrum, bridging the gap between "stellar-mass" black holes, which typically possess a mass roughly ten times that of our Sun, and supermassive black holes that weigh millions or even billions of times more.
The groundbreaking work was spearheaded by Andrew Mummery, a Martin A. and Helen Chooljian Member for the 2025–2030 term in the School of Natural Sciences at the Institute for Advanced Study, alongside Adelle Goodwin, a Forrest Research Foundation Fellow at Curtin University’s International Centre of Radio Astronomy Research located in Western Australia. Their findings represent a major step forward in understanding the fundamental mechanics of some of the most extreme objects in the universe.
Watching Black Holes Tear Stars Apart
Their study, titled "A universal critical accretion rate for black hole jet formation," was published in the prestigious journal Nature Astronomy. The research successfully brings together years of meticulous astronomical observations captured across multiple wavelengths of light. To build their comprehensive dataset, the team combined observations gathered by a global network of telescopes spanning America, Australia, India, South Africa, and space-based observatories.
The primary focus of the investigation centered on tidal disruption events—dramatic cosmic phenomena that occur when an unwary star wanders too close to a supermassive black hole. The immense gravitational forces exerted by the black hole generate brutal tidal stresses that ultimately rip the star completely apart. These violent events provided the research team with a rare, observational window into how a black hole behaves immediately after receiving a massive, sudden influx of fresh stellar material.
"We really wanted to figure out this massive puzzle," explained Mummery, elaborating on the motivations behind the study. "Why do some supermassive black holes blast out radio jets right after shredding a star, while others just sit there looking completely dormant, only to suddenly fire up their jets months or even years later?"
While black holes are frequently popularized in public media as the cosmic equivalent of vacuum cleaners, their actual feeding behavior is far messier and more chaotic. "When a black hole tears apart a star, it does not swallow everything neatly," noted Goodwin, describing the violent nature of the process.
Instead of a clean consumption, some of the shredded stellar material falls inward toward the event horizon, while a significant portion is violently expelled outward into the surrounding space in the form of powerful outflows and winds. These enormous cosmic "burps" are capable of carrying matter and energy across vast distances, playing a crucial role in shaping and regulating the evolution of the host galaxies that contain them.
A Faster Way to Study Supermassive Black Holes
For decades, astronomers have strongly suspected that black holes operate under the same basic physical laws, even when their individual masses vary by staggering margins. However, rigorously confirming this hypothesis has proven exceptionally difficult. Because supermassive black holes are so massive, changes in their environment and feeding behavior normally unfold over timescales spanning thousands or even millions of years—far too long for human astronomers to track in real time.
Tidal disruption events offer a clever observational workaround to this temporal barrier. When a star is catastrophically destroyed, the resulting feeding episode surrounding a supermassive black hole evolves rapidly, playing out over the course of just a few years. This compressed timeline grants scientists a much faster, highly accessible view of accretion and jet production processes that would otherwise remain completely opaque and impossible to track continuously.
The pivotal conceptual breakthrough behind the new study actually emerged in an unexpected setting. During an astrophysics conference held in Madrid, Mummery and Goodwin found themselves discussing their research in a local bar. Over the course of the conversation, they realized that a specific mathematical rule known to govern jet production in smaller, stellar-mass black holes might also apply directly to their supermassive counterparts.
Two Distinct Phases of Black Hole Jets
To rigorously test this hypothesis, the research team examined a sample of twenty tidal disruption events utilizing a multi-messenger approach. They gathered observations spanning optical light, ultraviolet light, X-rays, and radio waves, allowing them to track both the electromagnetic glow of the consumed material and the subsequent emergence of radio jets.
After thoroughly vetting the data, the researchers narrowed their sample down to ten high-quality events. For this refined group, they were able to reliably and accurately determine both the black hole’s fluctuating feeding rate and the precise timing of its corresponding radio outflows.
The subsequent analysis revealed two distinct periods during which these powerful jets can form.
The first phase occurs early in the timeline, shortly after the star’s destruction, while the black hole is actively consuming stellar material at an extremely high rate. The second phase, however, appears much later—anywhere from hundreds to thousands of days after the star was initially torn apart.
At this much later stage of the event, the black hole’s feeding rate drops significantly, falling to approximately two percent of its Eddington limit. The Eddington limit represents the theoretical threshold at which the outward pressure of radiation generated by the infalling matter perfectly balances the inward pull of gravity.
This specific two-percent threshold holds immense significance for astrophysics because it is already well-documented as a trigger for jet formation in much smaller, stellar-mass black holes residing within our own Milky Way galaxy. Finding this exact same threshold operating in the environment of supermassive black holes strongly indicates that this fundamental aspect of black hole physics functions in essentially the same manner across an enormous, multi-order-of-magnitude range of masses.
Predicting When Black Holes Will Erupt
Beyond deepening our theoretical understanding of accretion physics, this new discovery could also deliver substantial practical value for observational astronomers.
If researchers can reliably predict when a supermassive black hole is approaching the conditions necessary to produce a delayed jet, they can schedule telescope observations far more efficiently. This strategic planning would dramatically increase their chances of capturing these transient, short-lived events precisely as they happen, maximizing scientific output.
Such predictive capability could lead to a much more efficient allocation of heavily requested ground-based and space-based telescopes, reducing the amount of valuable observing time spent monitoring targets when little to no activity is expected.
The ability to accurately anticipate these cosmic eruptions is expected to become particularly valuable with the advent of major upcoming astronomical facilities. This includes the ambitious Square Kilometre Array radio telescope project, which is scheduled to begin collecting its first scientific data in 2028.
"We hope that our work will pave the way for even more profound discoveries about our universe," Mummery concluded, looking forward to how these findings will shape future observational campaigns.
