Black Holes of All Sizes Launch Jets at Same 2 Percent Feeding Threshold, Study Finds

Black holes have a reputation as cosmic sinkholes, but they are actually very messy eaters. When a star wanders too close to a supermassive black hole, gravity can tear it apart in a tidal disruption event, or TDE. Some stellar material falls inward and feeds the black hole, while some is flung outward in powerful jets and outflows. A study published in Nature Astronomy on September 17, 2026, led by Dr Adelle Goodwin of Curtin University's International Centre for Radio Astronomy Research and Dr Andrew Mummery of the Institute for Advanced Study in Princeton, offers a single rule for black holes of vastly different masses.

The Guardian reported on September 17, 2026 that scientists have solved the mystery of when black holes burp, meaning when they launch jets after feeding on stars and blast material enormous distances into space. Despite their reputation, black holes are actually very messy eaters, Goodwin said. Stars get destroyed further out than the event horizon, she explained, and only about half of the star that gets too close will end up eventually being swallowed. The other material is launched back into space in powerful jets and outflows, sometimes so large they can influence the entire evolution of a galaxy. That makes the timing of these burps more than a curiosity.

Phys.org reported on September 17, 2026 that black holes from stellar to supermassive size may follow one jet launching rule. The discovery shows black holes appear to fire off powerful jets at the same critical point in their feeding cycle, whether they are about 10 times the mass of the sun or millions of times heavier. The work was led by Goodwin, an astrophysicist at Curtin University's International Centre for Radio Astronomy Research and a Forrest Research Foundation fellow, with co-author Mummery from the Institute for Advanced Study in Princeton. Years of observations from telescopes in Australia, the United States, India, South Africa and space went into the finding.

Key Facts

The breakthrough came from asking why some black holes produce radio jets soon after tearing apart a star while others switch on months or years later. Goodwin said 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. The researchers analyzed 20 tidal disruption events using optical, ultraviolet, X ray and radio observations, narrowing the sample to 10 events where they could reliably model both the feeding rate and the timing of radio outflows. They found two distinct jet launching phases: one early, at extreme feeding rates, and a second hundreds to thousands of days later, when the feeding rate drops to about 2 percent of its Eddington limit, the point at which outward radiation pressure balances gravity. The same 2 percent threshold is already known to trigger jets in much smaller black holes in our galaxy.

The paper is titled A universal critical accretion rate for black hole jet formation. It was published in Nature Astronomy on September 17, 2026, with DOI 10.1038/s41550-026-02951-1. A preprint, arXiv:2602.14838, was submitted on February 16, 2026. The authors are Adelle J. Goodwin of the International Centre for Radio Astronomy Research at Curtin University in Perth and Andrew Mummery of the School of Natural Sciences at the Institute for Advanced Study in Princeton. Mummery is the Martin A. and Helen Chooljian Member for 2025 to 2030, and Goodwin is a Forrest Research Foundation Fellow.

Nature Astronomy reported on September 17, 2026 that the study shows tidal disruption events launch outflows during a super-Eddington accretion phase and a second, physically distinct outflow at a critical accretion rate of about 0.02 Eddington. That value, roughly 2 percent, is the same as the critical accretion rate for state transitions observed in accreting stellar-mass black holes. The agreement across such vastly different mass scales strongly indicates that a single, scale-invariant physical process governs jet launching in all black holes, according to the paper.

Eurasia Review reported on September 18, 2026 that an international collaboration co-led by an Institute for Advanced Study scholar uncovered a universal rule governing jet launching. The pivotal moment occurred in a bar in Madrid, where Mummery and Goodwin realized the same rule dictating jet launches in small black holes applied to supermassive ones.

Analysis

The bigger picture here is that scale invariance turns a puzzling variety of black hole behavior into a single predictive rule. For decades, astronomers have studied stellar-mass black holes in our galaxy and supermassive black holes in distant galaxies as if they belonged to separate regimes. Stellar-mass black holes evolve quickly, so their accretion state transitions and jet activity can be observed over human timescales. Supermassive black holes evolve slowly, and their tidal disruption events offer rare, years-long windows into the birth and evolution of an accretion flow. The new work connects those two worlds by showing that the same critical accretion rate, about 0.02 Eddington, marks the delayed jet phase in both.

What this really means is that the mass of a black hole may not change the underlying physics of how it launches jets. The paper argues that the agreement in this critical accretion rate across vastly different mass scales strongly indicates a single, scale-invariant physical process. If that is correct, then the 2 percent threshold is not a coincidence or a peculiarity of small black holes. It is a fundamental marker of how accretion and outflow couple. The early, super-Eddington phase and the later, low-accretion phase are physically distinct, yet both are part of the same feeding cycle. The delayed jet switches on when the black hole has consumed enough material that its feeding rate drops to the critical point, much as a smaller black hole does.

Mummery framed the original puzzle in stark terms. 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? The answer appears to be that the black hole is not random. It follows a schedule set by its accretion rate. Goodwin said the physics does not seem to care how big they are. That simplicity is powerful because it makes the timing of jets predictable. Instead of monitoring a tidal disruption event for years with no clear idea of when a radio signal might appear, astronomers can focus on the window when the accretion rate approaches the critical threshold.

Why It Matters

The immediate practical benefit is better use of radio telescopes. Tidal disruption events are rare and unpredictable. If astronomers know that a delayed jet should appear only when the black hole's feeding rate falls to about 2 percent of the Eddington limit, they can schedule observations more efficiently, reduce wasted telescope time and catch the moment of jet launch more reliably. Goodwin said the finding would let scientists precisely predict when jets are released, narrowing observation windows and freeing up precious telescope time. Independent reaction came from Dr Sara Webb, an astrophysicist at Swinburne University who was not involved in the research. She said the study showed that supermassive black holes behave rather predictably at two distinct periods in their evolution and tied this behavior to smaller stellar-mass black holes.

The result also matters for the Square Kilometre Array, or SKA, whose low-frequency component sits in Western Australia. The Australian government has invested 387 million dollars in the SKA, and the total project cost exceeds 2 billion dollars. The SKA is set to begin collecting scientific data in 2028. A predictive rule for black hole jets could help target the SKA and other radio telescopes at the right events at the right times, maximizing the return on that investment. More broadly, the finding speaks to how galaxies evolve. The jets and outflows from black holes can blast material across staggering distances and influence the evolution of their host galaxies. Only about half of the star that gets too close to the black hole is ultimately swallowed, and the rest is ejected.

Next Up

The next steps will involve testing the rule with more tidal disruption events and with additional multi-wavelength observations. The team already used optical, ultraviolet, X ray and radio data from telescopes in Australia, the United States, India, South Africa and space. Future campaigns can focus on the 2 percent Eddington threshold, watching for the delayed jet as the accretion rate drops. The SKA, scheduled to begin collecting scientific data in 2028, is expected to play a major role in those follow-up studies, especially for low-frequency radio observations of outflows.

Mummery said the team hopes the work will pave the way for even more profound discoveries about the universe. Goodwin's conclusion is equally direct: the physics does not seem to care how big they are. If that statement holds up, then black holes from stellar-mass objects of about 10 to 50 solar masses to supermassive giants of hundreds of thousands to billions of solar masses all follow one jet launching rule, set by a critical accretion rate of about 0.02 Eddington. The mystery of when black holes burp may be largely solved, and the answer is a threshold that applies across the cosmos.