Chandra Resolves Why Black Holes Hit the Brakes On Growth (phys.org) 27
alternative_right shares a report from Phys.org: Astronomers have an answer for a long-running mystery in astrophysics: why is the growth of supermassive black holes so much lower today than in the past? A study using NASA's Chandra X-ray Observatory and other X-ray telescopes found that supermassive black holes are unable to consume material as rapidly as they did in the distant past. The results appeared in the December 2025 issue of The Astrophysical Journal.
[...] The team ran tests of the three main possible scenarios currently being considered for the slowdown of black hole growth. These options were: could the decline in black hole growth be caused by less efficient rates of consumption, or by smaller typical black hole masses, or by fewer actively growing black holes? Their analysis of the data, extending over billions of years of cosmic history, led them to the conclusion that black holes are indeed consuming material less rapidly the later they are found after the Big Bang. The researchers expect this trend of slower-growing black holes to continue into the future.
[...] The team ran tests of the three main possible scenarios currently being considered for the slowdown of black hole growth. These options were: could the decline in black hole growth be caused by less efficient rates of consumption, or by smaller typical black hole masses, or by fewer actively growing black holes? Their analysis of the data, extending over billions of years of cosmic history, led them to the conclusion that black holes are indeed consuming material less rapidly the later they are found after the Big Bang. The researchers expect this trend of slower-growing black holes to continue into the future.
DNRTFA (Score:5, Insightful)
I'm guessing:
1) The cloud of material surrounding the black hole normalizes over time just like a planetary disk. At some point, pretty much everything that can intersect with the black hole already has, and only random collisions create new infalling material.
2) When the black hole does feed, it produces a lot of high energy activity just beyond the event horizon, which pushes material away before it can cross.
Re: (Score:3)
I'm guessing:
1) The cloud of material surrounding the black hole normalizes over time just like a planetary disk. At some point, pretty much everything that can intersect with the black hole already has, and only random collisions create new infalling material.
2) When the black hole does feed, it produces a lot of high energy activity just beyond the event horizon, which pushes material away before it can cross.
They outline and reference many parameters affecting growth but we can summarize:
3)Early in the universe a greater density and unconsolidated small galaxies, clouds, and clusters ensured a higher collision rate bringing in new material. While later in the development of the universe the consolidation under gravity meant less available mass and less perturbation effects that is helpful in bring new shipments of food.
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Eddington Limit [Re:DNRTFA] (Score:3)
2) When the black hole does feed, it produces a lot of high energy activity just beyond the event horizon, which pushes material away before it can cross.
For reference, that is known as the "Eddington limit [cambridge.org]" (on the rate of black hole accretion).
Almost as if... (Score:5, Insightful)
unable to consume material as rapidly as they did in the distant past
It's almost as if time slowed down around them the more they eat...
Re:Almost as if... (Score:4, Interesting)
unable to consume material as rapidly as they did in the distant past
It's almost as if time slowed down around them the more they eat...
While funny and insightful the time dilation occurs primarily above half the speed of light while gravitational pull occurs at all speeds. Natural objects only statistically reach these speeds on a significant basis within a low number of its horizon size widths which is a couple of AU while the gravitational pull is significant at over light years to tens of thousands of light years and significant for attracting and concentrating gas even if weak compared to the galactic gravitational field. Because we know black holes grow, time dilation is more of a weak plug in the drain of the bathtub of material it attracts with gravity.
Its important to note that the summary does not state a reason why we have super massive black holes extremely early in the universe, such as observations of red dots that are ultra massive stars a hundred thousand or even a million suns that direct collapse into the very large category of black holes without needing to feed at all. Despite that, the paper still applies because it does not focus on size but instead growth rate under many parameters including growth rates where the observed brightness to theoretically maximum brightness is decreasing.
Re:Almost as if... (Score:4, Interesting)
unable to consume material as rapidly as they did in the distant past
It's almost as if time slowed down around them the more they eat...
That's not the reason. Time slows down (from the perspective of a far away observer) as objects approach the event horizon. It doesn't matter if the black hole is small or big...it slows down by the same amount, the only question is where. The event horizon has a larger radius when it's big, and it has a smaller radius when it's small.
In both cases, from the perspective of a far away observer NOTHING ever crosses the event horizon, whether the black hole is small or big. It slows down as it approaches that point, and at the event horizon itself, time stops completely, so it will freeze there for eternity. You won't be able to see that, instead you see the light that it emits being redshifted as it has to climb the black hole's gravity well, eventually becoming too red-shifted to be detected, and it's effectively black.
In both cases, from the perspective of the object falling in, time is passing, and it crosses the event horizon without even knowing that it's there. Well, for a very large black hole, it doesn't notice anything, for a very small black hole, tidal effects cause spaghettification before crossing the event horizon, so it's going to notice something and have a bad time. But it won't be the event horizon, it's just the difference in the force of gravity across the length of the object.
So, the reason it slows down consumption is not related to the time dilation. Using your terms, "it's almost" as physicists spend their lives studying these things, and therefore if it seems obvious to the the layman reading a slashdot article, they've already considered it and either accepted, dismissed it, or tested it.
Proximity To Matter? (Score:2)
Re: Proximity To Matter? (Score:2)
Re: Proximity To Matter? (Score:3)
The issue is probably that the big bag won't fit in the overhead bin. Pull some of the matter out of the big bag and it might be able to be squished enough to fit.
Other black holes pack more slowly now, so everything fits.
If you insist on packing so much matter into the big bag so quickly, you're going to have to gate check it.
Chandra is a marvel (Score:5, Interesting)
Stupid(?) Astrophysics question: (Score:2)
Shouldn't the super-fast rotation of massive black holes counteract at least some of their gravity vertical to it's axis? Could that - at least hypothetically - eventually cause a black hole to break apart into bits of regular non-black-hole matter, if it spins fast enough?
Sorry if I'm sounding silly here, I'm a 5th-grader when it comes to astrophysics but perhaps someone with knowledge could offer some insight?
Re: (Score:2)
Black holes can evaporate via some weird physics (and Stephen Hawkings' pop explanation is apparently wrong even as a simplification and he knew it...), but normal physical processes do not apply.
A black hole can't break apart. Any energy you add to the black hole to attempt it would only make the black hole gain mass.
Re: (Score:2)
Shouldn't the super-fast rotation of massive black holes counteract at least some of their gravity vertical to it's axis? Could that - at least hypothetically - eventually cause a black hole to break apart into bits of regular non-black-hole matter, if it spins fast enough?
Sorry if I'm sounding silly here, I'm a 5th-grader when it comes to astrophysics but perhaps someone with knowledge could offer some insight?
While I'm not an astrophysicist, my understanding is that physics, along with everything else, breaks down inside the event horizon, so no matter how fast the black hole is spinning, once something reaches that event horizon, the only way back out is via the radiation we sometimes see escaping black holes. It's not coming back out as regular matter unless something catastrophic happens that I'm not sure we've ever seen observational data to prove is possible.
Re: (Score:1)
While I'm not an astrophysicist, my understanding is that physics, along with everything else, breaks down inside the event horizon, so no matter how fast the black hole is spinning, once something reaches that event horizon, the only way back out is via the radiation we sometimes see escaping black holes.
Nothing breaks down. You can cross it in a space ship and not even know if you are not looking out your window and the black hole is big enough. The event horizon is simply when escape velocity reaches c.
Re: (Score:2)
You can cross it in a space ship and not even know
Eventually. Due to gravitational time dilation, you cannot reach the event horizon until some time after the heat death of the universe. Of course, to you it will appear as thought you are just coasting in. To the rest of the universe, you'll never quite make it.
Except that the mechanism of Hawking radiation will appear to intensify from your point of view. What we see many light years away may appear to be a very weak energy flux. But compress that into your frame of reference and billions of years of pho
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This is a bit silly (Score:3)
Duh, have you seen gas prices lately (Score:1)
The real truth (Score:1)
I love news that says... (Score:2)
Simple explanation: (Score:2)
Editor: rewrite (Score:2)
What is the word "resolved" doing in the headline?
I know I can't... (Score:2)
Consume as much as I did when I was younger...