Are Tiny Black Holes Hiding Within Giant Stars? (science.org) 43
sciencehabit shares a report from Science Magazine: Grunge music: a source of validation for a generation of disaffected youth. And a surprising source of scientific inspiration for Earl Bellinger of the Max Planck Institute for Astrophysics. While listening to Soundgarden's 1994 hit Black Hole Sun 2 years ago, he contemplated a curious question: Might itty-bitty black holes from the dawn of time be lurking in the hearts of giant stars? A new study by Bellinger and colleagues suggests the idea is not so far-fetched. Astronomers could detect these trapped black holes by the vibrations they cause on the star's surface. And if there's enough of them out there, they could function as the mysterious dark matter that holds the universe together.
The researchers found that the black holes would sink to the star's core where hydrogen atoms undergo fusion to produce heat and light. At first, very little would happen. Even a dense stellar core is mostly empty space. The most microscopic of the black holes would have a hard time finding matter to consume and its growth would be extremely slow, Bellinger says. "It could take longer than the lifetime of the universe to eat the star." But larger ones, roughly as massive as the asteroid Ceres or the dwarf planet Pluto, would get bigger on timescales of only a few hundred million years. Material would spiral onto the black hole, forming a disk that would heat up through friction and emit radiation. Once the black hole was about as massive as Earth, it would produce significant amounts of radiation, shining brightly and churning up the star's core like pot of boiling water. "It will become a black hole -- powered object rather than fusion-powered object," says study co-author Matt Caplan, a theoretical physicist at Illinois State University. He and his colleagues have dubbed these entities "Hawking stars."
The European Space Agency's Gaia satellite has spotted about 500 such anomalously cool giant stars, known as red stragglers, Bellinger says. To figure out whether these might actually be hiding a black hole, he says, astronomers could tune in to the particular frequencies at which the stars vibrate. Because a Hawking star would churn throughout its interior, rather than just in the topmost layers like an ordinary red giant, it would be expected to thrum with a particular combination of frequencies. Such waves can be detected in the way the star's light pulses and throbs. Bellinger is applying for funding to study the known red stragglers and see whether any display the characteristic vibrations of a black hole. The study has been published in The Astrophysical Journal.
The researchers found that the black holes would sink to the star's core where hydrogen atoms undergo fusion to produce heat and light. At first, very little would happen. Even a dense stellar core is mostly empty space. The most microscopic of the black holes would have a hard time finding matter to consume and its growth would be extremely slow, Bellinger says. "It could take longer than the lifetime of the universe to eat the star." But larger ones, roughly as massive as the asteroid Ceres or the dwarf planet Pluto, would get bigger on timescales of only a few hundred million years. Material would spiral onto the black hole, forming a disk that would heat up through friction and emit radiation. Once the black hole was about as massive as Earth, it would produce significant amounts of radiation, shining brightly and churning up the star's core like pot of boiling water. "It will become a black hole -- powered object rather than fusion-powered object," says study co-author Matt Caplan, a theoretical physicist at Illinois State University. He and his colleagues have dubbed these entities "Hawking stars."
The European Space Agency's Gaia satellite has spotted about 500 such anomalously cool giant stars, known as red stragglers, Bellinger says. To figure out whether these might actually be hiding a black hole, he says, astronomers could tune in to the particular frequencies at which the stars vibrate. Because a Hawking star would churn throughout its interior, rather than just in the topmost layers like an ordinary red giant, it would be expected to thrum with a particular combination of frequencies. Such waves can be detected in the way the star's light pulses and throbs. Bellinger is applying for funding to study the known red stragglers and see whether any display the characteristic vibrations of a black hole. The study has been published in The Astrophysical Journal.
Why would tiny black holes eat slowly? (Score:1, Insightful)
Re:Why would tiny black holes eat slowly? (Score:5, Informative)
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Such small black holes are usually theorized to be primordial
The biggest problem with this hypothesis is the lack of observational evidence. If dark matter is BHs, they would have five times the mass of ordinary matter, and we would see them everywhere, either by gravitational lensing or radiation emitted when they pass through gas clouds.
A black hole formed from a collapsed star has a minimum mass of 3.3 solar masses. If it is any smaller, it will form a neutron star or white dwarf instead. So far, we haven't seen a single BH smaller than that limit.
The evidence say
Scientific method (Score:5, Informative)
Such small black holes are usually theorized to be primordial
The biggest problem with this hypothesis is the lack of observational evidence. If dark matter is BHs, they would have five times the mass of ordinary matter, and we would see them everywhere, either by gravitational lensing or radiation emitted when they pass through gas clouds.
A black hole formed from a collapsed star has a minimum mass of 3.3 solar masses. If it is any smaller, it will form a neutron star or white dwarf instead. So far, we haven't seen a single BH smaller than that limit.
The evidence says that primordial black holes either don't exist or are rare.
It is theorized that black holes smaller than 3.3 solar masses are formed during the big bang, when the pressure/density of the universe was much higher. Such holes would have evaporated fairly quickly due to Hawking radiation, IIRC something like 100,000 years, and so all the primordial ones will have evaporated by now.
The hypothesis is that if a primordial black hole ended up in a star, the different environment would allow it to survive to the present day. Depending on the size of the black hole and the environment, such a situation is predicted to last longer than the expected lifetime of the star.
This is a hypothesis. The "gut-feel" implications of the hypothesis are that this might explain dark matter.
The hypothesis has testable predictions in the oscillation frequency of certain stars. I suspect that this would also change the lifetime and energy output signature of such stars, and so a survey of stars of specific types would show slight differences from the predicted output from fusion that would be explained by the black hole theory.
If true, the hypothesis would be an elegant explanation for dark matter, and probably worthy of a Nobel prize.
Next step is to construct an experiment, then run the experiment to confirm or deny the hypothesis.
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something like 100,000 years
A BH with a lifetime of 100,000 years would have a mass of 4 million metric tonnes and a radius of 6e-18 meters. That's a hundredth the radius of a proton and a millionth the volume.
Hawking Radiation Calculator [vttoth.com]
this might explain dark matter.
I don't see how. Could there be some teeny BHs inside of stars? Perhaps.
Could they add up to four times the mass of all the stars, dust, and gas in the Universe? I don't think so.
Next step is to construct an experiment, then run the experiment to confirm or deny the hypothesis.
I'm busy today and tomorrow. But I might have time to do this over the weekend.
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Could they add up to four times the mass of all the stars, dust, and gas in the Universe? I don't think so.
I recall reading a theory that suggested that plank scale black holes could never actually completely evaporate. Heisenberg uncertainty with quantum gravity theories or something. I am not a physicist so don't ask me to explain...
But, if true, there could be a swarm of plank scale black holes through out the universe, concentrated by the existing normal matter (i.e. galaxies). They are so small that they can't actually absorb matter and the direct gravitational effects of a single one are below detection
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I think the researcher probably mentioned that small black holes of the type they think might exist inside some stars could explain dark matter. Not just the ones in stars, all of them.
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I think the researcher probably mentioned that small black holes of the type they think might exist inside some stars could explain dark matter. Not just the ones in stars, all of them.
Our galaxy would have to contain trillions or quadrillions of such BHs to account for all the missing mass. They would be much more common than stars.
We would see gravitational lensing and radiation from interstellar matter falling in. Some of them would grow larger, form binary systems with stars, and we'd see the Doppler effect as they rotated.
But we see none of that.
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There is a (narrowing) mass window where primordial black holes could account for a large fraction of dark matter. It's becoming increasingly unlikely, but it's not impossible yet.
See especially figure 2:
https://www.frontiersin.org/ar... [frontiersin.org]
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I think you missed out an exponential of ten in that. Viz : 10^(trillions or quadrillions), not (trillions or quadrillions)^10.
We might - for the larger ones. For the smaller ones, they'd be below our detection limits. (This got thoroughly thrashed out when people were trying
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The lifetime of a BH against evaporation by Hawking radiation is very steeply dependent on it's mass. And what happens at small masses remains decidedly unclear.
Consider an evaporating BH. Each time a particle escapes by the Hawking process, it's mass decreases, so the gravity gradient near-but-outside it's event horizon (the ergosphere) in
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Five times the density - at the galactic scale and higher - of ordinary matter. Which, at the galactic scale means more than approximately 5 atoms of hydrogen per cu.cm, not 1 atom per cu.cm.
The smallest object detected by gravitational lensing is, IIRC, order of Jupiter-mass. (Several hundred Earth-masses.) Which is not incompatible with there being a significant mass d
Gravity [Re:Why would tiny black holes eat slowly? (Score:4, Interesting)
Yes, atoms are mostly empty space, and black holes that are that size would not bump into the protons buzzing around, but they have tremendous gravity and would effectively "pull" the core matter into themselves, probably very quickly.
Tiny black holes have the same gravity as any other object of the same mass. Gravity is very weak compared to other forces. A black hole with the mass of a car, for example, a ton or so, would have a schwartzshild diameter of about one quadrillionth of an Angstrom. It will have tremendous gravity right at the horizon, but even a trillionth of an angstrom away, not very much. A Hydrogen atom has a diameter of roughly an Angstrom, so no, the gravity isn't a big deal.
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The gravitaitonal acceleration of a one tonne object at one angstrom would be over half a billion g.
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I'm too lazy to check either your math or the OPs, but just because there's a large acceleration doesn't mean the particle actually falls into the black hole. It may violently slingshot around the black hole if it gets close, but the odds of actually hitting it look to be infinitesimal.
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You could lazily use the same argument to predict that any size black hole doesn't grow.
The growth rate of a micro black hole in a dense environment is expected to be limited by the Bondi rate or the Eddington limit depending on its size. The Eddington limit is imposed by radiation pressure. The Bondi rate by the speed of sound in the medium... basically, how fast new material moves in to replace the stuff that's consumed.
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Friction is a thing at subatomic scales. You just can't treat it quite as generally as you can at larger scales.
Anyway, as I said, the growth rate is limited by the speed of sound and radiation pressure. Not "missing the hole."
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As you say, "lazily". Lazily, I could also say that some meteorites would penetrate through the Earth just as well as they penetrate it's atmosphere, because there's less than a trillion-fold difference in density between atmosphere and core. (It's actually closer to a million-fold than a trillion fold, but "meh". That neutrinos can do this is worth remembering. Some people consider neutrinos as potential dark matter pa
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Yeah, numbers are important. You can argue lots of things if you're "too lazy" to use them.
I'm not sure whether they address any of your questions, but the paper has a bunch of references about the limiting factors on micro black hole growth. The article seems to link to an unrelated paper, but I think this is the one we're actually discussing:
https://iopscience.iop.org/art... [iop.org]
I suspect for a micro black hole you would treat it like a subatomic particle (fundamental particles have occasionally been theorized
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Yeah, it's not simple. Particularly for fundamental point-like particles (leptons, maybe neutrinos) Our physics can't put a size on (some) of these, which you could read as ha
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In general, when you're working at quantum distances, gravity is so week that it's simply ignored. As to why the weakest force of the four rules the macroscopic universe, I'll leave that as an exercise for the reader.
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Material falling into a black hole emits x rays, which exert outward pressure. The maximum rate a black hole can grow is achieved when that pressure just balances the black hole's gravity. That point, called the Eddington luminosity, is proportional to the black hole's mass.
Formulas: https://www.fabiopacucci.com/r... [fabiopacucci.com]
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Yes, atoms are mostly empty space
You might say "the probability density function of a proton, at least above a certain threshold, is generally low within the majority of an atom, outside the nucleus, as determined by this formula for this atom surrounded by these other atoms, magnetic flux, etc." for example. The concept of empty space breaks down on the quantum level.
sounds like bull (Score:1)
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Perhaps the board human is theorizing about physics because the surf is flat today.
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I saw what you did there
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Or even two short Plancks?
Grunge (Score:1)
Grunge is a fashion not a type of music.
Re: Ummmmm (Score:2)
Re: Ummmmm (Score:4, Informative)
nobody wants to subscribe to nonsence disguised as news
I know many people who subscribe to nonsense disguised as news.
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nobody wants to subscribe to nonsence disguised as news & information that cant be relied on
As there are millions of people that read and watch such programming every single day (example: Fox News), I would say your assertion is dead fucking wrong.
Time to roast a marshmallow (Score:1)
no Robert Forward ref? (Score:3)
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and "Dragon's Egg", where the neutron star was discovered by a grad student trying to determine whether there was a 5th black hole in there or only the 4 that had been previously demonstrated.
It is actually at the end of Dragon's Egg (Score:2)
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Truth. (Also, if I recall correctly, the cheela did reveal there was a fifth, so closure! :)
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