A couple of recent stories.
"Not long ago, the center of the Milky Way exploded" |
ScienceDaily (https://www.sciencedaily.com/releases/2019/10/191006120913.htm)
QuoteA titanic, expanding beam of energy sprang from close to the supermassive black hole in the centre of the Milky Way just 3.5 million years ago, sending a cone-shaped burst of radiation through both poles of the Galaxy and out into deep space.
That's the finding arising from research conducted by a team of scientists led by Professor Joss Bland-Hawthorn from Australia's ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and soon to be published in The Astrophysical Journal.
The phenomenon, known as a Seyfert flare, created two enormous 'ionisation cones' that sliced through the Milky Way -- beginning with a relatively small diameter close to the black hole, and expanding vastly as they exited the Galaxy.
So powerful was the flare that it impacted on the Magellanic Stream -- a long trail of gas extending from nearby dwarf galaxies called the Large and Small Magellanic Clouds. The Magellanic Stream lies at an average 200,000 light years from the Milky Way.
The explosion was too huge, says the Australian-US research team, to have been triggered by anything other than nuclear activity associated with the black hole, known as Sagittarius A, or Sgr A*, which is about 4.2 million times more massive than the Sun.
"The flare must have been a bit like a lighthouse beam," says Professor Bland-Hawthorn, who is also at the University of Sydney.
[Continues . . . (https://www.sciencedaily.com/releases/2019/10/191006120913.htm)
"Black holes stunt growth of dwarf galaxies" |
ScienceDaily (https://www.sciencedaily.com/releases/2019/10/191011165322.htm)
QuoteAstronomers at the University of California, Riverside, have discovered that powerful winds driven by supermassive black holes in the centers of dwarf galaxies have a significant impact on the evolution of these galaxies by suppressing star formation.
Dwarf galaxies are small galaxies that contain between 100 million to a few billion stars. In contrast, the Milky Way has 200-400 billion stars. Dwarf galaxies are the most abundant galaxy type in the universe and often orbit larger galaxies.
The team of three astronomers was surprised by the strength of the detected winds.
"We expected we would need observations with much higher resolution and sensitivity, and we had planned on obtaining these as a follow-up to our initial observations," said Gabriela Canalizo, a professor of physics and astronomy at UC Riverside, who led the research team. "But we could see the signs strongly and clearly in the initial observations. The winds were stronger than we had anticipated."
Canalizo explained that astronomers have suspected for the past couple of decades that supermassive black holes at the centers of large galaxies can have a profound influence on the way large galaxies grow and age.
"Our findings now indicate that their effect can be just as dramatic, if not more dramatic, in dwarf galaxies in the universe," she said.
[. . .]
"Larger galaxies often form when dwarf galaxies merge together," she said. "Dwarf galaxies are, therefore, useful in understanding how galaxies evolve. Dwarf galaxies are small because after they formed, they somehow avoided merging with other galaxies. Thus, they serve as fossils by revealing what the environment of the early universe was like. Dwarf galaxies are the smallest galaxies in which we are directly seeing winds -- gas flows up to 1,000 kilometers per second -- for the first time."
Manzano-King explained that as material falls into a black hole, it heats up due to friction and strong gravitational fields and releases radiative energy. This energy pushes ambient gas outward from the center of the galaxy into intergalactic space.
"What's interesting is that these winds are being pushed out by active black holes in the six dwarf galaxies rather than by stellar processes such as supernovae," she said. "Typically, winds driven by stellar processes are common in dwarf galaxies and constitute the dominant process for regulating the amount of gas available in dwarf galaxies for forming stars."
Astronomers suspect that when wind emanating from a black hole is pushed out, it compresses the gas ahead of the wind, which can increase star formation. But if all the wind gets expelled from the galaxy's center, gas becomes unavailable and star formation could decrease. The latter appears to be what is occurring in the six dwarf galaxies the researchers identified.
[Continues . . . (https://www.sciencedaily.com/releases/2019/10/191011165322.htm)]
Didn't know what to reply but here I am, thanks for sharing.
Really no need to reply, but I appreciate it nonetheless. It's my pleasure to bring interesting stories like this to HAF. :smilenod:
I thank you as well Recusant. Please keep up the most enlightening work.
Iv'e never know you to post something I wasn't interested.
Quote from: Recusant on October 17, 2019, 06:53:12 PM
Really no need to reply. :smilenod:
Well I wont then! ::)
Quote from: Tank on October 18, 2019, 01:48:48 PM
Iv'e never know you to post something I wasn't interested.
Grovelling creep!
(https://media3.giphy.com/media/e48mcLfU9zgFq/giphy.gif?cid=790b7611a99541895b05485fed95568908edfb637dbfad0e&rid=giphy.gif)
There's a documentary by PBS on Netflix called 'NOVA: Black Hole Apocalypse'. It's interesting, even if a little repetitive.
Not so recent, but very important nonetheless!
Astronomers have made a comprehensive observation of the process of a star being assimilated by a black hole. Insert obligatory sensationalist headline here. :maskwink:
"Star's Death by Spaghettification: Shredded by Black Hole As Astronomers Record" |
SciTech (https://scitechdaily.com/stars-death-by-spaghettification-shredded-by-black-hole-as-astronomers-record/)
Quote(https://i.imgur.com/4OWvCPW.gif)
This animation depicts a star experiencing spaghettification as it's sucked in by a supermassive black hole during a 'tidal disruption event'. In a new study, done with the help of ESO's Very Large Telescope and ESO's New Technology Telescope, a team of astronomers found that when a black hole devours a star, it can launch a powerful blast of material outwards. Credit: ESO/M. Kornmesser
A rare blast of light, emitted by a star as it is sucked in by a supermassive black hole, has been spotted by scientists using telescopes from around the world.
The phenomenon, known as a tidal disruption event, is the closest flare of its kind yet recorded, occurring just 215 million light-years from Earth. It is caused when a star passes too close to a black hole and the extreme gravitational pull from the black hole shreds the star into thin streams of material — a process called 'spaghettification'. During this process some of the material falls into the black hole, releasing a bright flare of energy which astronomers can detect.
Tidal disruption events are rare and not always easy to study because they are usually obscured by a curtain of dust and debris. An international team of scientists led by the University of Birmingham were able to study this event in unprecedented detail because it was detected just a short time after the star was ripped apart.
Using the European Southern Observatory's Very Large Telescope and New Technology Telescope, the Las Cumbres Observatory global telescope network, and the Neil Gehrel's Swift Satellite, the team was able to monitor the flare, named AT2019qiz, over a six-month period as it grew brighter and then faded away.
[Continues . . . (https://scitechdaily.com/stars-death-by-spaghettification-shredded-by-black-hole-as-astronomers-record/)]
Godditit. :levitate:
Spaghettification (spelling?) has long been theorized. Now to see it in action is something else.
I've always found the idea of primordial black holes intriguing. This article does a fair job for a pop-science write-up of the topic via a paper describing what a personal encounter with one of those microscopic nightmare things might entail. I vaguely recall the Niven story mentioned at the beginning, but read it a long time ago.
"What Would Happen if a Tiny Black Hole Passed Through Your Body?" |
Universe Today (https://www.universetoday.com/170952/what-would-happen-if-a-tiny-black-hole-passed-through-your-body/)
QuoteIn 1974, science fiction author Larry Niven wrote a murder mystery with an interesting premise: could you kill a man with a tiny black hole? I won't spoil the story, though I'm willing to bet most people would argue the answer is clearly yes. Intense gravity, tidal forces, and the event horizon would surely lead to a messy end. But it turns out the scientific answer is a bit more interesting.
On the one hand, it's clear that a large enough black hole could kill you. On the other hand, a black hole with the mass of a single hydrogen atom is clearly too small to be noticed. The real question is the critical mass. At what minimum size would a black hole become deadly? That's the focus of a new paper on the arXiv.
The study begins with primordial black holes. These are theoretical bodies that may have formed in the earliest moments of the Universe and would be much smaller than stellar-mass black holes. Anywhere from atom-massed to a mass several times that of Earth. Although astronomers have never found any primordial black holes, observations do rule out several mass ranges. For example, any primordial black hole smaller than 1012 kg would have already evaporated thanks to Hawking radiation. Anything larger than 1020 kg would gravitationally lens stars in the Milky Way. Since we haven't detected these lensing effects, they must at the very least be exceedingly rare. If they exist at all.
[Continues . . . (https://www.universetoday.com/170952/what-would-happen-if-a-tiny-black-hole-passed-through-your-body/)]
The paper is open access (PDF):
"Gravitational Effects of a Small Primordial Black Hole Passing Through the Human Body" |
arXiv (https://arxiv.org/pdf/2502.09734)
QuoteAbstract:
The gravitational effects of a primordial black hole (PBH) passing through the human body are examined, with the goal of determining the minimum mass necessary to produce significant injury or death. Two effects are examined: the damage caused by a shock wave propagating outward from the black hole trajectory, and the dissociation of brain cells from tidal forces produced by the black hole on its passage through the human body.
It is found that the former is the dominant effect, with a cutoff mass for serious injury or death of approximately MPBH > 1.4×1017g. The number density of primordial black holes with a mass above this cutoff is far too small to produce any observable effects on the human population.
:devil2: :haironfire: :zombie:,,,, contemplating the affect of a black hole..............?????
https://www.sciencedirect.com/science/article/pii/S0370269321006109 ?
Quote from: zorkan on February 22, 2025, 01:20:14 PMhttps://www.sciencedirect.com/science/article/pii/S0370269321006109 ?
Indeed. That paper is considerably beyond my level of physics. The
Universe Today article does mention the hypothesis that dark matter is primordial black holes.
Dark matter might be passing through your body right now.
https://www.techexplorist.com/small-black-hole-passes-human-body/97115/#google_vignette
Maybe this is what the 2nd Law works off.
Neutrinos, higher energy photons and "all sorts" of other-such crap constantly pass through your body.
The less reactive stuff "just" passes through. Photons and the like may bump into things with more vigor and cause some unfortunate consequences.
In any case, dark matter would be far from unique in passing through you in large numbers completely unnoticed.
Quote from: Asmodean on February 27, 2025, 11:02:22 AMPhotons and the like may bump into things with more vigor and cause some unfortunate consequences.
Explain.
High [enough] energy photons are also called gamma rays.
They can "dislodge" nuclei in the DNA, causing mutations that can cause cancers and such-like.
Only likely to be a very low risk unless there has been an accident in a nuclear power plant or bomb.
https://www.cancer.gov/about-cancer/causes-prevention/risk/radiation#:~:text=High%2Denergy%20radiation%2C%20such%20as,made%2C%20tested%2C%20or%20used.
https://www.nasa.gov/directorates/esdmd/hhp/risk-of-radiation-carcinogenesis/#:~:text=Increased%20radiation%20exposure%20in%20the,later%20in%20an%20astronaut's%20life.
Also, Dark Lightning (https://www.rmets.org/metmatters/dark-lightning)
From the article, a person near one such flash can receive a full lifetime's dose of radiation.
Indeed, there is a statistical chance of getting cancer from radiation exposure.
You could get a nasty melanoma from being out in the sun for one hour, but you are highly unlikely to. Or you could be near a nuclear power accident, receiving a high but not lethal dose of rads and, upon recovering from radiation sickness, be just fine - though that too is unlikely.
I have been treated for skin cancer. Basal and squamous cell carcinoma.
May have been hiding away for years.
Something to do with my blue eyes, apparently.
https://www.nhs.uk/conditions/melanoma-skin-cancer/causes/#:~:text=Ultraviolet%20(UV)%20light%20is%20the,people%20can%20also%20get%20it.
I have had many of those things. If discovered early they are removed by a squirt of liquid nitrogen. If developed a bit more, then minor surgery, if left to grow for a long period of time, then more serious surgery.
The least convenient BCC that I have had was one my eyelid. Hospital, general anasthesia, etc. The guy who did the surgery was pretty good at it and did not wreck my eyeball.
Bccs and Sccs are manageable and are not likely to kill you. Melanoma, on the other hand, are potential widow makers.
ive got eye surgery in the morning to replace a clouded lens with a plastic one. should improve things substantiallt, if it works as well as the other one did.
^ Good medicine! My eye doctors are making noises about my impending lens replacements.
its quite significant for me, as i have to main decent visual acuity to kerp my commercial drivers license. if i fail the vision test, i have no job.
Right. I think my left eye has the maximum thickness lens, as I can barely make out the letters with it at the DMV, and in fact, I make mistakes. I look at the line I read with my left eye after doing so, and can tell. Changing the lens in that eye would improve my vision both from the clarity and different focal properties. I doubt that I'll get it to 20/20 with the surgery, though.
apparently all i have to do is get three consecutive letters correct in the third? row and i pass.
I may've got 3 correct. That was back in October, so dim and misty past, at this point. People with one eye are allowed to drive; I know a few.
Quote from: Icarus on March 12, 2025, 02:56:26 AMI have had many of those things. If discovered early they are removed by a squirt of liquid nitrogen. If developed a bit more, then minor surgery, if left to grow for a long period of time, then more serious surgery.
The least convenient BCC that I have had was one my eyelid. Hospital, general anasthesia, etc. The guy who did the surgery was pretty good at it and did not wreck my eyeball.
Bccs and Sccs are manageable and are not likely to kill you. Melanoma, on the other hand, are potential widow makers.
Went out for a walk one May day without a hat. Back in the car I noticed a blister on the side of my head that wasn't there before.
Scalpel off the blister at the hospital. All done, or so I thought. More serious op later to remove what was beneath.
Then all clear.
With all that radiation the main reason why we never set foot on the moon?
Don't mean to start a moon debate.
Just wondering how many black holes are up there and what would be the effect on health.
The universe is full of holes.
We might be living inside a mega massive one.
ISS is only 250 miles above us.
Why did we go to the moon in the first place?
Was it to see if it's hollow and artificial?
Why does it perfectly obscure the sun in an eclipse?
Quote from: zorkan on March 13, 2025, 11:39:32 AMWhy does it perfectly obscure the sun in an eclipse?
The why is a matter of mathematics
results in a world poetic symmetry
So we all look up and say just so
Yes but supposing the moon is alien-made as a calling card to stabilize the earth.
We are too stupid to consider now, but one day it will dawn on us.
Did you know that if we could manufacture a black hole we could travel the universe in just a few earth years?
All is explained in this rare book, of which I own a copy of a copy.
https://www.amazon.co.uk/Iron-Sun-Crossing-Universe-Through/dp/0340232315
Quote from: Dark Lightning on March 13, 2025, 12:18:23 AMI may've got 3 correct. That was back in October, so dim and misty past, at this point. People with one eye are allowed to drive; I know a few.
yes, a class C civilian driver.
i have a class A commercial. i cant keep that category with only one eye in any jurisdiction i know of
fascinating.
the aenesthesia is something called . . .brusic?
anyway, it keeps you conscious but groggy. during the procedure i could perceive the two ends of the forceps entering the corneal chambers to extract th e pieces of the destryed lens. i kept asking the surgeon to comment on what he was doing but i got no satisfaction there. thats a shame, because how often do you get to learn something like that?
anyway, it takes but a moment to do. the surgeon set the day aside for the procedure and closed his business office. did my surgery and ten others.
so far the incision is smoothing over. i wasnt supposed to drink alcohol for 24 hours, but after two beers everything appears to be going as well as i can expect.
more seriously, i have to stay in a dust-free environment for a week, and refrain from any contamination. that makes sense, because the incision is left open-- no sutures , staples, or glue. so any contaminants that get in there get permanently incoprporated into the schlera.
bad news.
Glad to hear that the procedure seems to have been a success. I know several people who've had them done and been pleased with the results.
Not sure how an open incision ends up without some sort of bleb on the eyeball. I guess if it's far enough away from the lens, the effect would be minimal.
they go in from the side, break the lens up, then suction out the pieces.
so its just the lateral schlera rhat gets cut up.
eyes heal quick, and after about 6 hours most of the discomfort is gone. vision is already better, even with tbe normal inflammation and swelling.
no work for a week tho. im pissed because im forced to take time off but i cant do anything dirty.
dirty things are my life.
This one got onto the US's public radio news, and perhaps elsewhere. I'd bet a fiver that it got onto at least Radio 4 from the BBC, if not their television news. So there's a good chance the remaining lucky few here have already heard tell of the vanishing star.
"A Giant Star Vanished, And Scientists Think a Black Hole Is to Blame" |
ScienceAlert (https://www.sciencealert.com/a-giant-star-vanished-and-scientists-think-a-black-hole-is-to-blame)
QuoteOne of the brightest stars in the Andromeda galaxy quietly collapsed into a black hole without any of the fanfare of a spectacular supernova.
What makes this startling discovery even more remarkable is that the first signs of the transformation were recorded back in 2014 – data that is crucial for understanding the different ways black holes can form after the death of a giant star.
"This has probably been the most surprising discovery of my life," says astronomer Kishalay De of Columbia University in the US, who led the research. "The evidence of the disappearance of the star was lying in public archival data, and nobody noticed for years until we picked it out."
When a massive star many times heavier than the Sun dies, it's not expected to go quietly. Once nuclear fusion in the core can no longer generate sufficient outward pressure against the inward pull of gravity, the core collapses.
This can send a giant shock tearing outward through the star, triggering a supernova explosion that sends the star's outer material flying, while the core transforms into either a neutron star or a black hole.
However, this is not the only way this transformation can take place. In some scenarios, the outward shock stalls. Instead of ripping the star apart, the explosion fizzles out, and the material ends up falling back onto the newly formed black hole. Because this is a much less dramatic process than a supernova, clear evidence of it is relatively rare.
"Unlike finding supernovae, which is easy because the supernova outshines its entire galaxy for a few weeks, finding individual stars that disappear without producing an explosion is remarkably difficult," De explains (https://news.columbia.edu/news/scientists-capture-clearest-view-yet-star-collapsing-black-hole).
Only one such event had been documented previously, a star recorded vanishing around 2010 in a galaxy 22 million light-years away. Now, by carefully looking over archival observations of the Andromeda galaxy, De and his colleagues have found another, and it's even clearer than the previous example.
M31-2014-DS1 was a supergiant star that started out about 13 times the mass of the Sun and shone brightly, even across the 2.5 million light-year distance between the Milky Way and Andromeda.
Then, in 2014, NASA's NEOWISE telescope recorded it suddenly shining more intensely in infrared, increasing its brightness by about 50 percent over about two years.
Then, between 2016 and 2022, it dimmed dramatically to the point where, by 2023, it completely vanished from view in optical wavelengths.
[Continues . . . (https://www.sciencealert.com/a-giant-star-vanished-and-scientists-think-a-black-hole-is-to-blame)]
The paper (https://www.science.org/doi/10.1126/science.adt4853) is behind a paywall, but I found a revised preprint version. Though I haven't gone into the paper yet, the abstract from the preprint is identical to the published version.
"Disappearance of a massive star in the Andromeda Galaxy due to formation of a black hole" |
arXiv (https://arxiv.org/abs/2410.14778)
QuoteWhen a massive star reaches the end of its lifetime, its core collapses and releases neutrinos that drive a shock into the outer layers (the stellar envelope). A sufficiently strong shock ejects the envelope, producing a supernova. If the shock fails to eject it, the envelope is predicted to fall back onto the collapsing core, producing a stellar-mass black hole (BH) and causing the star to disappear. We report observations of M31-2014-DS1, a hydrogen-depleted supergiant in the Andromeda Galaxy. In 2014, it brightened in the mid-infrared, then from 2017 to 2022, it faded by factors of ≳ 104 in optical light (becoming undetectable) and ≳ 10 in total light. We interpret these observations, and those of a previous event in NGC 6946, as evidence for failed supernovae forming stellar-mass BHs.
This could as easily go in the James Webb Telescope thread. A cool mystery in the deep reaches of spacetime: A supermassive black hole that appears to have formed before its galaxy.
By the way, I don't agree with the article's implication that at some point we'll have black holes completely figured out. On the other hand "somewhere in the future" could be thousands of years, so . . .
"The Weirdness of Early Universe SMBHs Gets Even Weirder" |
Universe Today (https://www.universetoday.com/articles/the-weirdness-of-early-universe-smbhs-gets-even-weirder)
QuoteSomewhere in the future, there's a finish line in the marathon to understand supermassive black holes (SMBH). We can't say how close we are, or what the final results will be. But astrophysicists keep going, confident that with each passing landmark, the finish draws nearer.
The effort to understand them became more earnest when the JWST was launched. Astrophysicists were suprised to find many SMBH in the early Universe. According to the understanding at the time, there shouldn't have been enough time for them to become so massive so soon.
New research is adding to the difficulty in understanding SMBH, turning it from a race into an obstacle course. Working with the JWST, researchers have found a SMBH with 50 million solar masses that appears to predate its host galaxy. This discovery is a direct challenge to what we thought we know about SMBH.
Astrophysicists understood, or thought they understood, that SMBH growth goes something like this: a massive star in a galaxy collapses into a black hole at the end of its life. This stellar-mass black hole grows by accreting surrounding material, and by merging with other stellar mass black holes doing the same thing. Galaxies also merge, driving their black holes to merge with them. Eventually, the process creates large galaxies with SMBH that can have billions of solar masses. It was still somewhat mysterious how small stellar mass black holes could be the seeds for much more massive SMBH, but the basic process was outlined.
Or so it was thought.
But now that the JWST has found an SMBH that appears to predate its galaxy, new questions demand answers.
[Continues . . . (https://www.universetoday.com/articles/the-weirdness-of-early-universe-smbhs-gets-even-weirder)]
There are two papers out on this topic, both open access. The abstracts get technical rather quickly, but my practice is to link to the actual papers:
"A direct black-hole mass measurement in a little red dot at high redshift" |
Nature (https://www.nature.com/articles/s41586-026-10579-4)
"A black hole in a near pristine galaxy 700 Myr after the big bang" |
Monthly Notices of the Royal Astronomical Society (https://academic.oup.com/mnras/article/548/1/staf2109/8607050)
In lieu of the abstracts, a press release. :shrug:
"Webb reveals black hole that formed before its galaxy" |
ESA Webb News (https://esawebb.org/news/weic2609)
QuoteWhich comes first, the galaxy or the black hole? Scientists have long thought it could be the galaxy: large stars within an existing galaxy consume their fuel and collapse to form black holes, which can gobble up surrounding material and merge over time to form more massive entities. But it's hard to figure out how black holes millions to billions of times the mass of the Sun, thousands of which have now been detected in the early Universe, could have grown so quickly from such small seeds.
Now, researchers using Webb have detected clear evidence that some supermassive black holes were enormous from the beginning, forming without a stellar collapse phase, and without a significantly more massive host galaxy to feed them.
[Continues . . . (https://esawebb.org/news/weic2609)]
Two items on black holes appeared in the pop science sites this past week. :dance:
"Black hole collisions may follow entropy law, offering simpler remnant predictions" |
Phys.org (https://phys.org/news/2026-07-black-hole-collisions-entropy-law.html)
QuoteWhen two black holes orbit each other, they eventually spiral inward and collide in one of the most violent phenomena in the universe. The event is so energetic that it significantly distorts the universe around it. It emits gravitational waves—ripples in the fabric of spacetime—that are strong enough to be detected with precision instruments on Earth even when they originate billions of light-years away.
These gravitational waves carry information about the event that physicists use to predict the size of the merger's resulting new, larger black hole—referred to as a remnant. But accurate predictions involve complex equations originally developed by Einstein as part of his theory of general relativity that require supercomputers to solve.
Now, a team of researchers led by physicists at Penn State has shown that there may be a simpler way, which also points toward a deeper understanding of the physics contained in those complex equations.
"The final black hole after a merger is ringing like a struck bell, and it radiates away more gravitational waves until it settles into a calm, stable state described by just two numbers—its final mass and spin," said Monica Rincon-Ramirez, a postdoctoral scholar in physics in the Penn State Eberly College of Science and the first author of the paper.
"The question we asked is: Can we predict what that final state looks like using arguments from thermodynamics?"
[. . .]
The new work suggests that once the energy and angular momentum—a measure of the system's rotational motion—carried away by gravitational waves are properly accounted for, the final black hole appears to be the state that maximizes entropy, the measure of randomness in a system, tracking the natural tendency of the universe to go from a state of order to a state of chaos.
"Entropy is essentially a measure of disorder, or more precisely, of how many ways something can be arranged," said Vaishak Prasad, a postdoctoral researcher in astronomy and astrophysics at Penn State and an author of the paper.
"A messy room has high entropy—there are countless ways things can be strewn about. A perfectly tidy room has low entropy—there are only a few arrangements that count as 'tidy.' Nature tends to drift toward high-entropy states simply because there are more of them. Our results suggest that black hole mergers do something similar."
The team developed what they call the "maximum entropy conjecture for black hole mergers," which is strikingly similar to ordinary thermodynamics.
[Continues . . . (https://phys.org/news/2026-07-black-hole-collisions-entropy-law.html)]
The paper (https://journals.aps.org/prl/abstract/10.1103/hvp6-ydbq) is behind a paywall.
QuoteAbstract:
The final state of a binary black hole merger is predicted with high precision by numerical relativity, but could there be a simple thermodynamic principle within general relativity that governs the selection of the remnant? Using post-Newtonian relations between the mass 𝑀 (including the binding energy) and angular momentum 𝐽 of quasicircular, nonspinning binaries, we uncover a puzzling result: When the binary's instantaneous 𝑀 and 𝐽 are mapped to those of a hypothetical Kerr black hole, the corresponding entropy exhibits a maximum during the evolution.
This maximum occurs at values of 𝑀 and 𝐽, strikingly close to those of the final remnant predicted by numerical relativity. Consistent behavior is observed when using the relation between 𝑀 and 𝐽 obtained from numerical relativity evolution.
Although this procedure is somewhat ad hoc, the agreement between the masses and spins of the final state obtained from numerical relativity and the results of this maximum entropy procedure is remarkable, with agreement to within a few percent when using either post-Newtonian or numerical relativity results for 𝑀 and 𝐽. These findings allow us to propose an entropy maximization conjecture for binary black hole mergers, hinting that thermodynamic principles may govern the selection of the final black hole state.
A bit dry, but intriguing. Perhaps at least a hint of a breakthrough. On to the second item:
"Gravitational waves reveal hidden populations within black hole mergers" |
Phys.org (https://phys.org/news/2026-07-gravitational-reveal-hidden-populations-black.html)
QuoteEvery time two black holes spiral together and merge, the resulting ripples in spacetime encode information about their masses and spins—the rate and direction at which each one rotates.
Astronomers can extract these properties from the gravitational-wave signal, but the picture is often incomplete: While some binaries formed from pairs of stars that lived and died together, others came together later, pulled into orbit by chance encounters in crowded stellar environments. Because these two pathways leave subtly different imprints on mass and spin, sifting through hundreds of detections to spot broader patterns has been a persistent challenge.
The first team's study, led by Cailin Plunkett at MIT, built a model that focuses on two well-measured spin parameters, capturing how a black hole's spin aligns with its orbital motion. The second study, led by Sharan Banagiri at Monash University in Australia, took a more open-ended approach, letting the data itself dictate how many distinct groups were present without assuming a particular formation story in advance.
Despite their different starting points, both teams identified a population of unusually massive black holes that stood apart from the rest, each roughly 40 times the mass of the sun or heavier.
Plunkett's team found that these heavyweights carry fast, randomly oriented spins consistent with black holes built from earlier mergers rather than stellar collapse. Banagiri's team reached a similar mass threshold and also found high spins in this group—though without the same clear signature of a merger origin. This prompted some caution about the interpretation.
Together, these findings offer some of the strongest evidence to date that a portion of observed black hole mergers are "second-generation" events, born from black holes that had already merged once before—rather than from the collapse of massive stars.
This distinction could ultimately help explain how black holes end up in a mass range otherwise thought to be off-limits, and how the seeds of the supermassive black holes at galaxies' centers might have grown. As gravitational-wave detectors grow more sensitive to these massive binaries, the boundaries between subpopulations could soon become clearer.
[Link to full article. (https://phys.org/news/2026-07-gravitational-reveal-hidden-populations-black.html)]
Both the first (https://journals.aps.org/prl/abstract/10.1103/n6p4-ftgq) and the second (https://journals.aps.org/prl/abstract/10.1103/blyb-lqv6) paper mentioned are behind paywalls. The abstracts include a fair bit of LaTex notation and arcane jargon; the links are there if anybody wants to check them out.