Black Holes Burp on Cue: Astronomers Find a Universal Jet-Launching Rule

Black holes have a reputation as the Universe’s most voracious eaters, swallowing anything that drifts too close to their gravitational grip. But according to new research led from Western Australia, they are far from tidy diners. When a black hole tears apart a star, it consumes some of the debris and hurls the rest back into space in spectacular jets and outflows — cosmic ‘burps’ that can blast material across enormous distances and reshape the galaxies around them. Now, an early-career astrophysicist at Curtin University has helped reveal that these burps obey a surprisingly universal timetable, one that appears to hold true whether the black hole involved weighs ten times as much as the Sun or millions of times more.

The discovery, accepted for publication in the prestigious journal Nature Astronomy, shows that black holes appear to switch on their powerful jets at the same critical point in their feeding cycle, regardless of their mass. The work was led by Dr Adelle Goodwin, an astrophysicist at Curtin University’s International Centre for Radio Astronomy Research (ICRAR) and a Forrest Research Foundation Fellow, together with co-author Dr Andrew Mummery of the Institute for Advanced Study in Princeton. Their finding emerged from years of painstaking work piecing together observations from telescopes across Australia, America, India and South Africa, as well as instruments in space, all trained on rare and dramatic events in which stars are torn apart by supermassive black holes.

The central question that drove the research was deceptively simple: why do some black holes produce radio jets soon after ripping a star apart, while others seem to stay silent for months or even years before suddenly lighting up? For astronomers monitoring the sky, the inconsistency was frustrating. A tidal disruption event — the technical term for a star being shredded by a supermassive black hole — can flare brilliantly in optical, ultraviolet and X-ray light, yet the radio signature of a jet may arrive on a schedule that seems arbitrary from event to event. Without a predictive rule, telescope time was being spent largely on guesswork.

The breakthrough, Dr Goodwin recalls, did not happen at a telescope console but in a bar in Madrid during a conference, where she and Dr Mummery realised that the same jet-launching rule already known from small black holes in our own Galaxy also appeared to hold for supermassive ones. ‘We were looking at these events and asking why the timing was so different,’ Dr Goodwin said. ‘Then the pattern became clear. The delayed jets were appearing when the black hole’s feeding rate dropped to the same critical point already known from much smaller black holes. That was the moment we realised this was not just a quirk of one type of black hole, but it looked like a rule that applied across the Universe.’

Proving that black holes of wildly different masses share the same basic physics has long been one of the field’s stubborn challenges. The reason is time: supermassive black holes, sitting at the centres of galaxies with millions to billions of solar masses, normally evolve over thousands of years or longer. Watching one complete a full feeding cycle is simply impossible within a human career, let alone a single observing campaign. Stellar-mass black holes, by contrast, feed and flare on timescales of days to months, which is why much of what astronomers know about accretion and jet formation comes from these smaller objects in our Galaxy.

Dr Goodwin found a way around the timescale problem by exploiting tidal disruption events. When a star strays too close to a supermassive black hole, the immense tidal forces rip it apart, and the resulting debris forms a hot, swirling accretion disc as it spirals inward. Crucially, this compresses an entire supermassive black hole feeding episode into a few years rather than several millennia, giving astronomers a rare chance to watch the full process — from the initial stellar destruction to the late-time launch of jets — unfold in something close to real time.

To turn these fleeting events into a rigorous test, the researchers analysed twenty tidal disruption events using optical, ultraviolet, X-ray and radio observations. They narrowed the sample to ten events where they could reliably model both the black hole’s feeding rate and the timing of its radio outflows. The analysis revealed two distinct jet-launching phases. The first occurs early in the event, when the black hole is feeding at extreme rates near the peak of the disruption. The second arrives much later — hundreds to thousands of days after the star is first torn apart — and it is here that the universal rule emerges: the delayed jets ignite when the black hole’s feeding rate falls to roughly two per cent of its Eddington limit.

The Eddington limit is a fundamental benchmark in astrophysics, marking the point at which the outward pressure of radiation exactly balances the inward pull of gravity. Above it, radiation pressure tends to blow away infalling material; below it, matter can settle inward more steadily. Strikingly, the same two-per-cent threshold has long been known to trigger jet formation in stellar-mass black holes in our own Galaxy, objects that can be millions of times lighter than the supermassive monsters at the hearts of distant galaxies. ‘These black holes are separated by enormous differences in mass, but they appear to switch on their jets at the same point in the feeding process,’ Dr Goodwin said. ‘That tells us something fundamental about black holes: the physics does not seem to care how big they are.’

The implications extend well beyond satisfying theoretical curiosity. The finding neatly explains why some tidal disruption events produce radio jets quickly while others go quiet before flaring up months or years later — the late bloomers were simply waiting for their accretion rates to fall through the critical threshold. It also promises to make astronomers far more efficient users of some of the world’s most expensive and oversubscribed scientific instruments. ‘Radio telescopes are incredibly powerful, but knowing when to look is just as important as knowing where to look,’ Dr Goodwin said. ‘If we can anticipate when a black hole is more likely to launch a jet, we can run better targeted campaigns, waste fewer observations and improve our chances of catching these rare events at the moment they matter most.’

The timing of the discovery is particularly significant for Western Australia, which will host the low-frequency component of the Square Kilometre Array Observatory (SKA), one of the most ambitious radio astronomy projects ever conceived. The Australian Government has invested 387 million dollars in the SKA, whose total cost exceeds two billion dollars, and every hour of observing time on such a facility is precious. As next-generation surveys discover far more tidal disruption events than current instruments can, astronomers will need reliable ways to decide which events to follow and when. This research hands them a clear physical signal for when a black hole’s jet is most likely to appear. As Forrest Research Foundation Director Professor James Arvanitakis observed, the discovery shows why backing early-career researchers to pursue difficult, open-ended questions matters — a question funded without a predetermined answer has produced a result of international significance, sharpening how major scientific infrastructure is used and demonstrating the strength of Western Australia’s research ecosystem. The paper, ‘A universal critical accretion rate for black hole jet formation’, was published in Nature Astronomy on 17 September 2026.

Subject of Research: Universal critical accretion rate governing jet formation by black holes during tidal disruption events

Article Title: WA scientist helps crack black hole ‘burp’ mystery

Article References: WA scientist helps crack black hole ‘burp’ mystery. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: black holes, jets, tidal disruption events, accretion, Eddington limit, radio astronomy, supermassive black holes, Nature Astronomy, Curtin University, ICRAR, Square Kilometre Array, astrophysics