Summary
A Nature Astronomy study finds that tidal disruption events produce a second outflow when accretion falls to about 2% of the Eddington limit. The result points to a scale-invariant link between accretion and jet formation in stellar-mass and supermassive black holes.
Black holes ranging from stellar remnants to the supermassive objects at galactic centres appear to launch jets at the same low accretion threshold, according to a study published in Nature Astronomy on 17 September 2026.
Adelle J. Goodwin and Andrew Mummery analysed publicly available multiwavelength observations of selected tidal disruption events (TDEs), combining accretion-disc modelling, radio-data modelling and statistical tests. They report that TDEs produce an outflow during a super-Eddington accretion phase and a second, physically distinct outflow when the accretion rate reaches a critical level of approximately 2% of the Eddington limit: Lcrit ≈ 0.02 LEdd.
The authors identify this value with the threshold at which accreting stellar-mass black holes undergo state transitions associated with jet formation. Their conclusion is that the coupling between matter falling into a black hole and material expelled from its surroundings is scale invariant across vastly different black-hole masses.
A threshold seen in two kinds of black-hole systems
An accretion disc is a rotating flow of gas spiralling towards a black hole. As the flow changes, some of the available energy can emerge as radiation, winds or narrow, fast-moving jets. The Eddington luminosity is a reference level at which outward radiation pressure can balance the inward pull of gravity for a given object; the study expresses its critical transition as a fraction of this reference luminosity.
In stellar-mass black-hole systems, the relevant changes can be observed over relatively short periods. These systems are known to launch jets and outflows as they pass through critical accretion-rate thresholds. Supermassive black holes in active galactic nuclei are much harder to follow through an individual transition because their accretion flows evolve over timescales of thousands of years.
The reported agreement at approximately 0.02 LEdd connects those two regimes. The paper argues that a single physical process may govern the low-accretion-rate transition that enables jet launching in both types of system. It also presents the threshold as a basis for predicting which black holes are likely to launch jets and when.
Why tidal disruption events make the comparison possible
A TDE occurs when a star passes close enough to a supermassive black hole to be torn apart by tidal forces. The resulting debris forms an accretion flow whose evolution can be tracked over years rather than the much longer timescales typical of an established active galactic nucleus.
That makes TDEs a useful natural experiment. Researchers can observe the flow as it develops, follow its changing accretion rate and compare those changes with radio emission produced by outflows. The study says this framework accounts for both prompt outflows, launched early during the event, and delayed outflows that appear later as the accretion flow declines.
The result is significant because it links transient observations around supermassive black holes with the better-constrained state changes of stellar-mass systems. The authors also report that the framework explains the observed properties and detection rate of prompt and delayed TDE outflows, while providing a way to make future predictions about jet activity.