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It is well known that, from time to time, black holes produce matter jets along its axis of rotation, generally in both directions, and at very high speed. Most people think of black holes as cosmic vacuum cleaners that consume all the matter they attract to themselves, but that’s not entirely true. Not all the matter that falls toward the black hole’s event horizon (beyond which there is no return) actually crosses it. Any black hole has a rate at which it can consume matter, and the rate of matter infall is greater than the rate of consumption, the excess matter will emerge in a jet.
However, exactly when, during the process of matter consumption, the black hole emits a jet was unpredictable–until now. Further, those conditions appear to apply to both medium-sized black holes found around the Milky Way, and the supermassive black holes at the centers of galaxies.
One of the biggest mysteries the researchers wanted to explain was why black holes do not always launch jets at the same time.
When a supermassive black hole tears apart a star, it sometimes produces a powerful jet almost immediately. In other cases, the black hole appears relatively quiet for months or even years before suddenly producing a detectable radio outflow.
“Then the pattern became clear. 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.
“That was the moment we realized this was not just a quirk of one type of black hole, but it looked like a rule that applied across the Universe.”
When a passing star comes too close to a black hole, it is torn apart and its remnants are drawn into the orbit of the black hole. This is called a tidal disruption event, where the black hole’s feeding rate is dramatically increased. Sometimes, when the black hole’s feeding rate abruptly increases, it produces a jet rather promptly, but other times, a delay of months or years passes before the jet is observed. It turns out that the delayed jets appear when the black hole’s feeding rate falls below 2% of what’s called its Eddington limit.
The Eddington limit is a theoretical benchmark describing the point at which the outward pressure produced by radiation balances the inward pull of gravity. Astronomers use it to measure how intensely a black hole is feeding relative to a characteristic physical limit.
What makes the finding especially significant is that the same 2% threshold has already been linked to jet formation in much smaller black holes within our own Milky Way galaxy.
So there appears to be a universal behavior in jet formation for black holes of any size. When a tidal disruption is observed, astronomers will be able to estimate when a jet is expected to appear, and then look for it, rather than playing a guessing game.
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From A Pagan in Arizona:
From Lisa Needham’s story about presidential toadies fighting and sketchy goings-on with donations to the Kennedy Center, this comment by member 1BQ.
Diary: https://www.dailykos.com/stories/2026/10/15/800112539/news/trumps-worst-toadies-are-fighting/
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