Black Holes May Be Swallowing Invisible Matter That Slows the Movement of Stars (space.com) 82
For the first time, scientists may have discovered indirect evidence that large amounts of invisible dark matter surround black holes. The discovery, if confirmed, could represent a major breakthrough in dark matter research. Space.com reports: Dark matter makes up around 85% of all matter in the universe, but it is almost completely invisible to astronomers. This is because, unlike the matter that comprises stars, planets and everything else around us, dark matter doesn't interact with light and can't be seen. Fortunately, dark matter does interact gravitationally, enabling researchers to infer the presence of dark matter by looking at its gravitational effects on ordinary matter "proxies." In the new research, a team of scientists from The Education University of Hong Kong (EdUHK) used stars orbiting black holes in binary systems as these proxies.
The team watched as the orbits of two stars decayed, or slightly slowed, by about 1 millisecond per year while moving around their companion black holes, designated A0620-00 and XTE J1118+480. The team concluded that the slow-down was the result of dark matter surrounding the black holes which generated significant friction and a drag on the stars as they whipped around their high-mass partners.
Using computer simulations of the black hole systems, the team applied a widely held model in cosmology called the dark matter dynamical friction model, which predicts a specific loss of momentum on objects interacting gravitationally with dark matter. The simulations revealed that the observed rates of orbital decay matched the predictions of the friction model. The observed rate of orbital decay is around 50 times greater than the theoretical estimation of about 0.02 milliseconds of orbital decay per year for binary systems lacking dark matter. The study has been published in The Astrophysical Journal Letters.
The team watched as the orbits of two stars decayed, or slightly slowed, by about 1 millisecond per year while moving around their companion black holes, designated A0620-00 and XTE J1118+480. The team concluded that the slow-down was the result of dark matter surrounding the black holes which generated significant friction and a drag on the stars as they whipped around their high-mass partners.
Using computer simulations of the black hole systems, the team applied a widely held model in cosmology called the dark matter dynamical friction model, which predicts a specific loss of momentum on objects interacting gravitationally with dark matter. The simulations revealed that the observed rates of orbital decay matched the predictions of the friction model. The observed rate of orbital decay is around 50 times greater than the theoretical estimation of about 0.02 milliseconds of orbital decay per year for binary systems lacking dark matter. The study has been published in The Astrophysical Journal Letters.
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Dark matter? (Score:3)
Re:Dark matter? (Score:5, Informative)
Dumb question, I know, but .... what the heck is dark matter anyway?
Nobody knows. The first person to figure it out will get a trip to Stockholm.
But we know what it isn't. It isn't any form of baryonic matter, and it isn't micro-blackholes.
Will a spacecraft be smashed to bits when it cruises into dark matter
No. Dark matter does not interact with "normal" matter.
Do we have to worry about dark matter asteroids smashing into the earth?
No. Dark matter doesn't clump into asteroids or anything else.
Are there dark matter elements that we should add to the periodic table?
No. It makes no sense to talk about "elements" of non-baryonic matter.
Re:Dark matter? (Score:5, Informative)
"No. Dark matter does not interact with "normal" matter."
If the article is correct, and I do not know if it is, then dark matter must at least interact with gravitational fields produced by ordinary matter. So that sense it does interact with normal matter.
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Yes. It is wrong to say it doesn't interact with bryonic matter. It interacts only gravitationally. So the OP's question is basically, will a space craft be smashed only because of gravitaional energy? My guess is probably right and it is - no, things are "smashed" because molecules come close enough that they start repelling each other, converting the kinetic energy o the molecules into bond energy which above a threshold causes the bonds to break (at lower speeds, the bond energy is not enough, so it is d
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Yes. It is wrong to say it doesn't interact with bryonic matter. It interacts only gravitationally. So the OP's question is basically, will a space craft be smashed only because of gravitaional energy? My guess is probably right and it is - no
Probably correct but there is A family of models for dark matter that supposed primordial black holes left over from the Big Bang. We know they can’t be too small or they would have evaporated from Hawking radiation or been observed and we know they can’t be as massive as the sun or we would see the gravitational lensing and interactions with objects. But there is a sweet spot of low mass, where they would be Very hard to detect. Luckily our solar system came with several large detectors that
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Inflation energy inside the volume of black holes may be replenishing and growing black holes faster than any Hawking radiation can evaporate them, even without infalling matter.
https://www.imperial.ac.uk/new... [imperial.ac.uk]
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If the article is correct, and I do not know if it is, then dark matter must at least interact with gravitational fields produced by ordinary matter. So that sense it does interact with normal matter.
The article is a bit confusing in this regard, as it remains a bit vague on how this interaction works:
[..] which generated significant friction and a drag on the stars as they whipped around their high-mass partners.
Gravitational drag is something I can get my head around. But I have no clue how the mechanism behind this 'gravitational friction' would work, and the article does not clearly explain it.
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But I have no clue how the mechanism behind this 'gravitational friction' would work, and the article does not clearly explain it.
Apologies, although the article itself is not really clear about the mechanism, luckily someone in the comments jumped to our aid:
"If a star is moving inside a collisionless dark matter background, the star would exert a gravitational force to pull the dark matter particles toward it. Then a concentration of the dark matter particles would locate behind the star and exert a collective gravitational force on the star. This collective gravitational force would slow down the star, and the resulting effect is c
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Dumb question, I know, but .... what the heck is dark matter anyway?
Nobody knows. The first person to figure it out will get a trip to Stockholm.
But we know what it isn't. It isn't any form of baryonic matter, and it isn't micro-blackholes.
We barely know what a black hole is from millions of light years away, so perhaps we don't assume what "isn't". We barely know anything about the universe, with even the "known" universe being a tiny fraction of reality. Not surprising, since we're almost as clueless about what lies in the deepest parts of our own oceans.
What we DO know, is the definition of a "theory". We also know, humans can be wrong. Including astrophysicists, astrologists, and cosmologists.
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We barely know what a black hole is from millions of light years away
The closest BH is 1600 ly from Earth.
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IIUC, that theorem is about a space-time that doesn't exactly match the observed universe, but is mathematically easier to reason about. It *may* apply to the actual universe, or there may be an strongly analogous theorem, but I don't know that this is correct.
This is true of many theories in cosmology. The actual observed universe is too gnarly to model, so simplifying assumptions are made, with the hope that nothing vital was lost. IIUC the original theories of black holes assumed that they were non-ro
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The real problem for sorting out what a black hole is remains the lack of a renormalizable (quantum) theory of gravity. General Relativity breaks at densities where even light cannot escape body (hence the term "singularity", meaning literally where a mathematical model starts returning nonsense answers). At the densities we model for a black hole, GR becomes useless, but it is assumed that if we had a quantum explanation for gravity, and understood how it functioned at such extraordinary densities, we coul
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The closest BH is 1600 ly from Earth.
That we know of.
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We barely know what a black hole is from millions of light years away
The closest BH is 1600 ly from Earth.
And our achievements have traveled less than 30 light minutes away so far, which took decades to achieve.
Pretty sad when order-of-magnitude sized errors don't even matter.
Re: Dark matter? (Score:2)
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Actually voyager probes are at least 18 light hours away....
I stand corrected. Closer to 22 light hours now, but who's really counting when decades of effort have gotten humanity as far as your average Netflix binge.
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According to Nature, someone has recently been able to create artificial black holes in the lab.
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No. They've created models that in some ways are similar to black holes, and they HOPE that the similarities are sufficient that the results of the lab experiments reflect what the actual black holes do.
This is not a bad approach, but don't misunderstand it. It's often a short-cut to correct insights, but it also often doesn't match in the required manner. Think of it as producing a very strong hint of the thing matching (i.e. similar to) the result happening in the actual system. If you've modeled all
Corrections (Score:3)
But we know what it isn't. It isn't any form of baryonic matter, and it isn't micro-blackholes.
We know it is not baryonic matter but small, primordial black holes have not been ruled out yet. While there is no known mechanism to produce the latter but it is going to be a while before LIGO is sensitive enough to rule them out - or detect them via their collisions.
No. Dark matter does not interact with "normal" matter.
Yes, it does interact with matter at least via gravity because we see it through its gravitational effects on matter. It does not interact with matter through the electromagnetic force though otherwise it would interact with light and it wo
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There are lots of possibilities for "small primordial black holes". My preference is for ones a lot smaller than you are thinking of, and they would need to have been created REALLY early in the process. I assume that there is a minimum size (capture cross-section) for the emission of Hawking radiation, and when a black hole gets smaller than that it stops radiating. It will have mass, and probably a charge, but it's chance of capturing something, including another primordial black hole, would be essenti
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My preference is for ones a lot smaller than you are thinking of,
Very small Black Holes can be ruled out. The smaller a BH the more rapidly it decays through Hawking radiation. Dark Matter has to have survived from the Big Bang up to today, 13.7 billion years later since we see evidence for it both in the cosmic microwave background emitted ~300k years after the Big Bang and in the universe around us today.
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I don't think you actually read my post. I mentioned that, and what I expect to be the answer.
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"No. Dark matter doesn't clump into asteroids or anything else."
Are they sure? It should be able to clump up solely by gravity. Of course with no electromagnetic interactions to reinforce it it would fall apart in any stronger gravitational field.
So if a dark matter "asteroid" was about to collide with earth it would be shredded at the Roche limit, then the cloud of "particles" would pass right through the earth and end up as a dispersed cloud on a trajectory only altered by earth's gravity.
Or would somethi
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The simple models of dark matter can't clump. To get clumping you'd need dark matter that could interact with other dark matter in a non-elastic manner. I'm not really averse to that, but the math is going to get REALLY ferocious, and is probably insoluble without knowing more about the kinds of dark matter interactions.
Still, that's a fair objection. What's really true is that the models used to explain dark matter don't currently contain any features that would allow clumping.
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No. Dark matter does not interact with "normal" matter.
The whole point of "dark matter" was to explain the rotation of galaxies.
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I disagree. We don't know that "it isn't micro-blackholes". Just that if it is micro-blackholes, they must be (predominantly) primordial (i.e. from well before the re-ionization) AND there must be a minimal size at which they stop emitting Hawking radiation. I don't think that's unreasonable at all, as if their capture cross-section is too small they won't be able to capture half of a pair of virtual particles. What I can't see is any way to detect the presence of any small number of them (A large enou
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It's a particle cosmologists theorized must exist because without it a few observations don't match what the math predicts. Galaxy rotation speed, for example. If it exists, it interacts only gravitationally, what few attempts there have been to detect it directly showed no result. Ramming into dark matter would feel like nothing.
Particulate dark matter as a theory doesn't explain everything, i.e. it is not universally considered to be the final answer in cosmology. Some competing hypotheses are superfluid
Re: Dark matter? (Score:4, Funny)
what the heck is dark matter anyway?
It's the astrophysicists' version of a Keleven.
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The community prefers to give it a better name, given all the funding.
"Fucking clueless" doesn't bring in the dollars no matter how good you dance around a black hole.
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It is a made up astronomer fantasy material required to make their equations work.
So, either there is this bizarro stuff filling most of the universe which a bunch of folks are making their careers on.
Or
Their equations are wrong.
You decide.
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>Dark matter does not make the equations work. All scientists are in 100% agreement that the equations we have are wrong, because those equations do not predict our observations.
It absolutely does. It is used to add mass precisely because without it, some galaxies "spin too fast" according to General Relativity. The "wrong" (as you say) equations were used to estimate how much dark matter there is. This is a textbook case of hypothesizing an entity in order to make the mathematical predictions match obse
just sweep that stuff under the rug! (Score:3)
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It is a made up astronomer fantasy material required to make their equations work.
So, either there is this bizarro stuff filling most of the universe which a bunch of folks are making their careers on.
Or
Their equations are wrong.
You decide.
We need Richard Feynman back. We could all meet in his favorite strip club and get this stuff all figured out. https://www.tsbmag.com/2014/02... [tsbmag.com]
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Dumb question, I know, but .... what the heck is dark matter anyway?
Not dumb. Dark matter is a placeholder name for "Something is happening here, and we're not sure what it is."
It is unfortunate that it was named dark matter, in the same way that a scientific theory is named. Kinda confusing.
The public conflates "Theory" with a WAG - or Wild Ass Guess. In science the hypothesis is more like the WAG, and a theory is when the WAG's are shown to be pretty much correct.
At least that's my theory! 8^)
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Because it interacts weakly or not at all via electromagnetism, we don't know. The hopes were that at least one of the supersymmetry models, as an extension to the Standard Model of subatomic particles, where particles have a "superpartner", and some of these "superpartners" would only weakly interact (WIMP). Thus far there is no experimental evidence. Still, either there is some sort of matter that interacts gravitationally, or there's something wrong General Relativity. Since GR has been confirmed numerou
Re: Dark matter? (Score:2)
Dark matter isn't matter but rather a field D associated with the gravity field G analogous to how the magnetic field H and the electrical field E are bound.
There are 4 fundamental laws.
The first states that the divergence of G equals the mass density divided by gamma where gamma is the gravitational constant (better known as G). This is the universal law of gravity as discovered by Newton.
The second states that the divergence of D is zero; looking for dark matter monopoles is futile.
The third states that a
Observational accuracy? (Score:3, Insightful)
I'm astonished, and very sceptical, of their ability to distinguish orbital decay of 1ms per year versus predictions of 0.02ms per year, at a distance of over 3,000 light years.
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I've seen Dave click his stopwatch so fast it's amazing.
Dave could do it.
Re:Observational accuracy? (Score:4, Insightful)
I am not skeptical because that is 50x the difference.
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Whoosh!
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What does distance from an object have to do with periodic timing?
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I'm astonished, and very sceptical, of their ability to distinguish orbital decay of 1ms per year versus predictions of 0.02ms per year, at a distance of over 3,000 light years.
1ms is 1mhz
Our radio telescopes can measure frequencies in the terehertz range, which is a period of 100 microseconds.
These frequencies are trivial to accurately measure at distance.
We can even measure down at the picosecond range, although with less accuracy.
However two types of measurement that is very accurate at that level are in comparison of two objects at a distance in the same scale, and in comparison of one object from one moment in time to the next.
This is done by comparison, hardware that can sub
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What's NOT clear (to me) at that distance is that there isn't an interaction with some third body that's too small to see. They need observations on more than one system. Either that, or go out there an look, but that would take awhile.
OTOH, if there's a momentum transfer that's ongoing, there should be a fairly rapid decay into an different state over time, probably by ejecting the third body from the system. So that's another way to check, but I'm not sure how long the ejection should take.
Isn't dark matter supposed to speed up stars too? (Score:1)
" the dark matter dynamical friction model, which predicts a specific loss of momentum on objects interacting gravitationally with dark matter."
What about the stars that orbit too fast for F=ma predictions? Isn't that a case of a specific gain in momentum on objects interacting gravitationally with dark matter?
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What about the stars that orbit too fast for F=ma predictions? Isn't that a case of a specific gain in momentum on objects interacting gravitationally with dark matter?
Well, if you assume the only gravitational force is from normal matter then the f=ma prediction fails but if you assume a properly shaped cloud of dark matter, or halo, then f=ma works because there is an F that satisfies the math and correlates with reality for any m or a. The key is to have it be descriptive of reality with measurements only ever validating the model and for this dark matter halos seem to be on top so far. The dark matter halo won’t necessarily have the same speed or density as
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What about the stars that orbit too fast for F=ma predictions? Isn't that a case of a specific gain in momentum on objects interacting gravitationally with dark matter?
Not really. The Dark Matter is not giving momentum to the stars but rather its gravitational field is preventing the star from being flung out further from the galactic core where it would orbit more slowly - or even escape the galaxy since without DM galaxies would not exist in their current form.
Of course... (Score:4, Funny)
I'm thinking that any future ships sent to study this should be completely black [fandom.com] on the outside as well as ...
To compliment the black holes and dark matter.
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I'm thinking that any future ships sent to study this should be completely black [fandom.com] on the outside as well as ...
I don't recognize the story quote, but one thing is for sure. They didn't buy that ship at the Apple Store, like in the Star Trek movie.
To compliment the black holes and dark matter.
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... hitch hiker's, restaurant at the end of the universe. That was galactic level rock star Hot Black (sp?)'s ship.
It's been half of forever since I read them. I should reread the series and you should have a first go.
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"I'm thinking that any future ships sent to study this should be completely black"
Designed like my old Sony DVD player? Black buttons with symbols in slightly raised black plastic on a black panel on a black cabinet. And in that commendable Japanese workmanship the buttons were so well fitted you couldn't feel them either.
More than once I had to get a flashlight to find the control I needed.
A black hole swallowing dark matter... (Score:3)
Re: A black hole swallowing dark matter... (Score:3)
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Can I have instant toast and hot tea? I hate trying to time it so they're both ready together.
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Argument by incredulity is a fallacy. Now find a more effective argument, please.
Dark matter interaction (Score:2)
I thought dark matter didn't interact with normal matter except gravitationally? How could it create "drag"?
Re:Dark matter interaction (Score:5, Informative)
How could it create "drag"?
By gravitation. It's called Chandrasekhar friction, or Dynamical Friction [wikipedia.org].
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I thought dark matter didn't interact with normal matter except gravitationally? How could it create "drag"?
Don't worry about that - Republicans are working hard to eliminate drag.
Inaccurate summary (Score:1)
It says: "The team watched as the orbits of two stars decayed, or slightly slowed, by about 1 millisecond per year".
However, this is not how celestial mechanics works. If an orbiting body loses some total energy due to e.g. friction, it transfers to a lower orbit. And in the lower orbit, the period is lower and the orbital speed is higher. In other words, the orbiting body subject to friction, in fact, accelerates due to the reduction of the potential energy in the gravitational field over-compensating the
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The journalist is confused, and you're distracted by the word "slowed." The unit is milliseconds, so they're talking about the period.
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It says: "The team watched as the orbits of two stars decayed, or slightly slowed, by about 1 millisecond per year".
However, this is not how celestial mechanics works.
No, but given the distance from the object observed and our human accuracy, this is how rounding errors work.
Rounding errors don't refresh funding coffers though. Cool headlines about what may be going on 1000+ light-years away do.
come on! (Score:2)
Dark matter, black holes, come on! Now you're just making stuff up!! :-D
How does dark matter create drag (Score:2)
If dark matter interacts only through the gravitational force, how could an accreted cloud of dark matter create drag on a star whose orbit passes through it?
A given volume of dark matter particles would 'pull' the star forward in its orbit while approaching, and then would 'pull' the star backwards in its orbit by the same amount after it had passed through.
What is the effect that they are referring to as 'drag'? Could it just be stellar dust?
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If dark matter interacts only through the gravitational force, how could an accreted cloud of dark matter create drag on a star whose orbit passes through it?
Chandrasekhar friction [wikipedia.org]
Circular reasoning? (Score:2)
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Invisible Flashback (Score:2)
He, didn't Dark Matter Dynamical Friction open for the Talking Heads in 1978?
Black matter.... (Score:2)
sounds to me like some idea that we came up with so that our model of the universe works otherwise we just can't figure out where all the mass went. If we didn't have magic matter, I mean dark matter, then our precious model breaks. Maybe we need a better model.