Scientists pinpoint when black holes launch jets — SkimNews
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- Dr Adelle Goodwin of Curtin University and Dr Andrew Mummery of the Institute for Advanced Study published research in Nature Astronomy identifying two distinct phases when supermassive black holes fire jets after tearing apart stars.
- The second jet phase fires hundreds to thousands of days after the star is destroyed, when the black hole's feeding rate drops to about 2% of its maximum swallowing capacity — the same threshold known to trigger burps from much smaller stellar-mass black holes (10-50 times the sun's mass).
- The team studied 20 tidal disruption events using radio telescopes, the only frequency that captures jets and outflows as they move outward, resolving a timing mystery where burps had previously occurred anywhere from one to five years after a star was destroyed.
- Only about half of a star that crosses a supermassive black hole's gravitational threshold is actually swallowed; the rest is blasted back into space in jets powerful enough to influence the entire evolution of a galaxy.
- Dr Sara Webb of Swinburne University, who was not involved in the study, said the research shows supermassive black holes 'behave rather predictably at two distant periods in their evolution,' tying the behavior to patterns previously seen only in smaller stellar-mass black holes.
- Goodwin said the finding will let scientists precisely predict when jets will launch, narrowing observation windows and freeing up precious telescope time for the rare events.
Why it matters: The 2% feeding threshold acts as a universal trigger for jet launches across black holes of vastly different sizes, meaning researchers can now predict burps that previously arrived unpredictably anywhere from one to five years after a star was destroyed. That predictability directly translates into shorter, better-targeted telescope observations — a meaningful efficiency gain given how rare tidal disruption events are and how competitive radio telescope time remains.
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