Universal jet-triggering threshold found across black hole sizes
A study in Nature Astronomy reports that black holes of all sizes appear to launch jets when their accretion rate falls to roughly 2% of the Eddington limit. The pattern was observed in tidal disruption events, where supermassive black holes tear apart stars, and matches known behavior of smaller stellar-mass black holes in the Milky Way. The finding suggests a common physical mechanism for jet formation across mass scales.
The study combined multi-wavelength observations from telescopes on four continents and in space, tracking tidal disruption events where supermassive black holes shred passing stars. By compressing feeding cycles that normally take millennia into just a few years, these events let researchers compare jet behavior across vastly different mass scales. The critical threshold—roughly 2% of the Eddington limit—matches the known trigger point for stellar-mass black holes in our galaxy, suggesting a common accretion physics governs jet launch regardless of black hole size. The idea emerged during a casual conversation at a Madrid astrophysics conference, highlighting how collaborative insight can accelerate discovery.
This finding could sharpen predictions of when black holes emit jets, aiding astronomers in scheduling observations and interpreting radio signals from distant galaxies. It may also refine models of how jets influence galaxy evolution, with potential implications for understanding cosmic feedback processes. Society benefits indirectly through improved fundamental knowledge, though no immediate practical applications are expected. The universality hinted at here could inspire broader searches for similar scaling laws in other astrophysical phenomena, but confirmation across more events remains necessary before firm conclusions are drawn.