Astronomers discover a strange universal rule behind black hole eruptions
Scientists have discovered that black holes of vastly different sizes appear to launch powerful jets according to the same universal rule. The breakthrough could explain why some black holes suddenly erupt years after devouring a star and help astronomers predict when these spectacular outbursts will happen.
Key points
- Astronomers found black holes of vastly different masses follow the same rule for launching jets.
- Delayed jets appear when the black hole's feeding rate falls to about 2% of its Eddington limit.
- The discovery could help astronomers better target radio telescope observations.
Astronomers have discovered a universal rule that appears to govern when black holes launch powerful jets of material into space. The finding, published in Nature Astronomy, shows that black holes with masses ranging from about 10 times the Sun to millions of times the Sun activate their jets at the same critical stage of their feeding cycle.
The research was led by Dr. Adelle Goodwin, an astrophysicist at Curtin University's International Centre of Radio Astronomy Research (ICRAR) and a Forrest Research Foundation Fellow, with co-author Dr. Andrew Mummery of the Institute for Advanced Study in Princeton.
Insight from a Madrid bar
The breakthrough came after years of studying tidal disruption events, where supermassive black holes tear stars apart. By combining observations from telescopes in Australia, the United States, India, South Africa, and space, the scientists tracked how black holes behave as they consume matter.
Goodwin and Mummery realized the key pattern during a conversation at a scientific conference in Madrid. They recognized that the same rule known to govern jet formation in smaller black holes also applied to supermassive ones.
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. Adelle Goodwin
The 2% threshold
The team examined 20 tidal disruption events and selected 10 with reliable data on both the black hole's feeding rate and the timing of radio outflows. They found that delayed jets appear when the feeding rate drops to approximately 2% of the Eddington limit, a theoretical benchmark where radiation pressure balances gravity.
This same 2% threshold had already been linked to jet formation in much smaller black holes in the Milky Way. The discovery could help astronomers predict when delayed jets are likely to appear, improving the efficiency of radio telescope observations, including for the Square Kilometre Array Observatory (SKA) in Western Australia.
