Chasing dark matter with the oldest stars in the Milky Way

January 24, 2018, Princeton University
Barred Spiral Milky Way. Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA

Just how quickly is the dark matter near Earth zipping around? The speed of dark matter has far-reaching consequences for modern astrophysical research, but this fundamental property has eluded researchers for years.

In a paper published Jan. 22 in the journal Physical Review Letters, an international team of astrophysicists provided the first clue: The solution to this mystery, it turns out, lies among some of the oldest stars in the galaxy. 

"Essentially, these old stars act as visible speedometers for the invisible , measuring its speed distribution near Earth," said Mariangela Lisanti, an assistant professor of physics at Princeton University. "You can think of the oldest stars as a luminous tracer for the dark . The dark matter itself we'll never see, because it's not emitting light to any observable degree—it's just invisible to us, which is why it's been so hard to say anything concrete about it."

In order to determine which stars behave like the invisible and undetectable dark matter particles, Lisanti and her colleagues turned to a computer simulation, Eris, which uses supercomputers to replicate the physics of the Milky Way galaxy, including dark matter.

"Our hypothesis was that there's some subset of stars that, for some reason, will match the movements of the dark matter," said Jonah Herzog-Arbeitman, an undergraduate and a co-author on the paper. His work with Lisanti and her colleagues the summer after his first year at Princeton turned into one of his junior papers and contributed to this journal article.

Herzog-Arbeitman and Lina Necib at the California Institute of Technology, another co-author on the paper, generated numerous plots from Eris data that compared various properties of dark matter to properties of different subsets of stars.

Their big breakthrough came when they compared the velocity of dark matter to that of stars with different "metallicities," or ratios of heavy metals to lighter elements.

The curve representing dark matter matched up beautifully with the stars that have the least heavy metals: "We saw everything line up," Lisanti said.

"It was one of those great examples of a pretty reasonable idea working pretty darn well," Herzog-Arbeitman said.

Astronomers have known for decades that metallicity can serve as a proxy for a star's age, since metals and other heavy elements are formed in supernovas and the mergers of neutron stars. The small galaxies that merged with the Milky Way typically have comparatively less of these heavy elements.

In retrospect, the correlation between dark matter and the oldest stars shouldn't be surprising, said Necib. "The dark matter and these old stars have the same initial conditions: they started in the same place and they have the same properties ... so at the end of the day, it makes sense that they're both acted on only through gravity," she said.

Why it matters

Since 2009, researchers have been trying to observe dark matter directly, by putting very dense material—often xenon—deep underground and waiting for the dark matter that flows through the planet to interact with it.

Lisanti compared these "direct detection" experiments to a game of billiards: "When a dark matter particle scatters off a nucleus in an atom, the collision is similar to two billiard balls hitting each other. If the is much less massive than the nucleus, then the nucleus won't move much after the collision, which makes it really hard to notice that anything happened."

That's why constraining the speed of dark matter is so important, she explained. If dark matter particles are both slow and light, they might not have enough kinetic energy to move the nuclear "billiard balls" at all, even if they smack right into one.

"But if the dark matter comes in moving faster, it's going to have more kinetic energy. That can increase the chance that in that collision, the recoil of the nucleus is going to be greater, so you'd be able to see it," Lisanti said.

Originally, scientists had expected to see enough particle interactions—enough moving billiard balls—to be able to derive the mass and velocity of the dark matter particles. But, Lisanti said, "we haven't seen anything yet."

So instead of using the interactions to determine the speed, researchers like Lisanti and her colleagues are hoping to flip the script, and use the speed to explain why the direct detection experiments haven't detected anything yet.

The failure—at least so far—of the direct detection experiments leads to two questions, Lisanti said. "How am I ever going to figure out what the speeds of these things are?" and "Have we not seen anything because there's something different in the speed distribution than we expected?"

Having a completely independent way to work out the speed of dark matter could help shed light on that, she said. But so far, it's only theoretical. Real-world astronomy hasn't caught up to the wealth of data produced by the Eris simulation, so Lisanti and her colleagues don't yet know how fast our galaxy's are moving.

Fortunately, that information is being assembled right now by the European Space Agency's Gaia telescope, which has been scanning the Milky Way since July 2014. So far, information on only a small subset of stars has been released, but the full dataset will include far more data on nearly a billion .

"The wealth of data on the horizon from current and upcoming stellar surveys will provide a unique opportunity to understand this of dark matter," Lisanti said.

Explore further: Does dark matter annihilate quicker in the Milky Way?

More information: Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.120.041102

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72 comments

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Pkunk_
2.3 / 5 (9) Jan 24, 2018
When the floor falls off this theory, they will probably find out that dark matter never existed, or it was something in another dimension/multiverse which we can't even comprehend yet.
humy
4.1 / 5 (9) Jan 24, 2018
When the floor falls off this theory, ....

Are you assuming here that the theory must necessarily be wrong? If so, how can you rationally know this? Are you a qualified cosmologist or at least a qualified physicist? Have you got an alternative theory that has passed scientific peer preview? What makes you think you know better than other people smarter than you that have researched it for many years when you haven't? I for one don't assume I must know better than other people smarter than me (about something) who have properly researched it when I haven't. I think dark matter may or may not exist and its too early to tell.
javjav
4.3 / 5 (6) Jan 24, 2018
He has no f.idea about physics. The use of the "multiverse" term in this context tells you everything.
vlaaing peerd
4.6 / 5 (10) Jan 24, 2018
they will probably find out that dark matter never existed, or it was something in another dimension/multiverse


I think you're more troubled about the name than having trouble with the theory. For you it might have been better if it were called "unknown extra gravity causing stuff". Really, there's not much theory about DM.

1. There is more gravitational interaction in star systems than we can account for with visible matter. We are sure this happens, we are seeing it.

2. The most simple explanation is that it is matter causing the extra gravity, like everyting else in the universe. We are however not seeing it. That's why it was named dark matter but could just as well been named "unknown extra gravity causing stuff".

That's basically it about the whole damm theory and good scientists are trying to find out what exactly it is. How can this be incorrect?
antialias_physorg
4 / 5 (12) Jan 24, 2018
When the floor falls off this theory

Dark matter is not a theory (therefore it is impossible for its 'floor to fall off'). 'Dark matter' is a label for an observed effect. Period.

The observations are real. *Whatever* we find that explains these observations will be 'dark matter'.

Whether it turns out to be actual matter or something entirely different is besides the point. The label 'dark matter' does not imply that the possible explanations are limited to massive particles (it just means that what we observe is an effect the likes of which we otherwise only know from matter - so it made sense to call it 'dark matter').

I wish people would get this straight before getting all huffed up.
dogbert
3 / 5 (8) Jan 24, 2018
No, the term 'dark matter' is not just a place holder or a label. From the time the term was created to the present, all efforts at finding 'dark matter' are looking for matter which cannot be seen.

If you were looking for the cause of gravitational anomalies, you would use terms like gravitational anomaly.

After looking for over 70 years for 'dark matter' without finding a single particle, that hypothesis is overdue for being discarded. When your hypothesis consistently fails to produce results, it is time for new hypotheses.
dogbert
3.7 / 5 (3) Jan 24, 2018
mackita,
It may well be a combination of several things, and probably is the result of more than one thing. But as long as we focus on a hypothesis which has failed for as long as most people live, we are unlikely to find the real reasons our models fail to match our observations.
antialias_physorg
3.7 / 5 (9) Jan 24, 2018
No, the term 'dark matter' is not just a place holder or a label.

The actual theories have specific names (MACHOS, WIMPS, etc. ) and these can be tested for and falsified. There is no theory that is named 'dark matter theory'.

From the time the term was created to the present, all efforts at finding 'dark matter' are looking for matter which cannot be seen.

The reason for this is isn't because people only have matter-based theories but because no one knew how to test any of the other ones (e.g. MOND type theories).

With the LIGO data from the latest neutron star crash MOND could be tested because if MOND were real the light from the crash should have had a significant lag with respect to the gravitational wave (turns out they appeared at the same time, so MOND is not a viable theory - or at the very least the parameters of it are seriously constrained)
Benni
1.6 / 5 (7) Jan 24, 2018
Great News flash.........so now, the latest news for failure to isolate Dark Matter.

Failure is now attributed to low Kinetic Energy impact on baryonic matter because the stuff has such low velocity as it meanders aimlessly throughout the galaxy. This Cosmic Fairy dust just sort of floats aimlessly throughout the galaxy as our solar system plows it's way through those humongus DM clouds that never seem to have much velocity compared to our solar system moving through those clouds at 245 km/sec.

I guess when Lisanti compared these "direct detection" experiments to a game of billiards, he forgot to add the kinetic energy impact our solar system would have at a velocity 245 km/sec as if that also is too miniscule to trigger impact detection.

OK, Lisanti, at least give us your best guess for the velocity of this cosmic fairy dust, we'll add that to the known kinetic energy impact our solar system will have on those immensely thick clouds of DM, and VOILA, we'll know.
Benni
1.6 / 5 (7) Jan 24, 2018
Their idea is, the dark matter manifests itself at higher altitudes (when its drag by Earth body gets diminished) and/or in special type of detectors, which are sensitive to its motion.


Yeah, "Their idea". And so far what has their special detectors gotten them? El zippo, but you just gotta love the low kinetic energy narrative, it's certainly a NEW idea sure to keep the debate going among the overage Trekkie culture living here on this site, right Schneibo?
Benni
1 / 5 (5) Jan 24, 2018
The dark matter is just placeholder for observational data


It is not a "placeholder" for anything to do with "data", there are only "observational" pics of formations of Spiral galaxies that a guy who hated Einstein tried to draw preposterous conclusions for.

There is no "data" giving credence to zany Zwicky's concept of clouds of counter gravitational matter preventing Spiral Galaxies from imploding. I guess you don't know this is where the entire concept of cosmic fairy dust began in the first place.

Go study a little of Zwicky's track record to get a better idea where zany cosmology comes from, yeah from a guy who believed rockets wouldn't work beyond Earth's atmosphere because rocket exhaust would have nothing to push against to create forward thrust........yeah, that's zany & that's Zwicky.
RNP
4 / 5 (12) Jan 24, 2018
Benni again shows himself a committed shadow boxer by trying to berate real science with a sentence consisting of a false picture of both history and science.

There is no "data" giving credence to zany Zwicky's concept of clouds of counter gravitational matter preventing Spiral Galaxies from imploding.


@Benni
Let me remind you, YET AGAIN, that;

1) Zwicky never worked on spiral galaxies - his DM related work was on galaxy clusters.

2) Dark matter is NOT "counter graviational" - it ADDS to the gravitational effect.

3) Spiral galaxies would expand, not "implode", if DM was not there.

All these facts are easily checked by Googling them. So, you really should learn some relevant physics (and history) if you do not want to keep making such a fool of yourself.
Benni
1 / 5 (6) Jan 24, 2018
All these facts are easily checked by Googling them. So, you really should learn some relevant physics (and history) if you do not want to keep making such a fool of yourself.


......and there you go Mr Freelance Journalist, as usual directly off the plantation of Funny Farm Science.

Hey, do you know what a Differential Equation looks like? Maybe you, like jonesy, ran into them in high school Algebra Class?
RNP
3.9 / 5 (14) Jan 24, 2018
@Benni
Here is a self-evident differential equation for you;

The rate at which Benni produces nonsense (N) is inversely proportional to his understanding (U) of the subject under discussion, i.e;

dN/dt = C/U.

Do you know how to solve it?...... I'll tell you ; stop talking.
fthompson495
1 / 5 (6) Jan 24, 2018
There is evidence of the superfluid dark matter every time a double slit experiment is performed, as it is the medium that waves.
Benni
1 / 5 (6) Jan 24, 2018
@Benni
Here is a self-evident differential equation for you;

The rate at which Benni produces nonsense (N) is inversely proportional to his understanding (U) of the subject under discussion, i.e;

dN/dt = C/U.

Do you know how to solve it?...... I'll tell you ; stop talking.


Learn how to properly write the DE for per capita growth rate..............coming from a Jounalist, what else could be expected. When YOU don't write it correctly, YOU or anyone else will never find the solution for it.
RealityCheck
1 / 5 (5) Jan 24, 2018
@Benni, can't stay long again today, busy still; so briefly re your above response to @mackita:
...Zwicky's track record...
Again, you appear to have missed/ignored my previous reminders to you/everyone re what Zwicky ACTUALLY posited re DM as explanation for certain 'anomalous-seeming' gravitational dynamics/motions re galaxy clusters:

Zwicky ACTUALLY ONLY EVER posited ORDINARY MATTER in various energetic/structural/flow etc 'states' which made it 'too dark/faint to see/detect' with THEN telescopes/instruments/estimates (due low intrinsic luminosity and/or distance too great)!

OK? It was NOT ZWICKY who posited NON-NORMAL (ie, "EXOTIC") DM; so your ire should be directed at OTHERS, NOT ZWICKY re "exotic" DM furphy!

MOREOVER, we are NOW finding much of the 'previously-dark/missing' matter! And it's ALL ORDINARY KNOWN 'stuff'; and increasingly BETTER DETECTED by NEWER/BETTER telescopes/instruments!

So DM is ORDINARY and BEING DETECTED, as ZWICKY PREDICTED! :)
Benni
1.7 / 5 (6) Jan 24, 2018
So DM is ORDINARY and BEING DETECTED, as ZWICKY PREDICTED! :


So odd then that Zwicky gets the godfather credits for all this DM Slop & Swill cosmic fairy dust.
RealityCheck
1 / 5 (6) Jan 24, 2018
@Benni.
So DM is ORDINARY and BEING DETECTED, as ZWICKY PREDICTED!
So odd then that Zwicky gets the godfather credits for all this DM Slop & Swill cosmic fairy dust.
It's understandable, given the lax/miss-'education' of most 'professional' cosmologists/hack 'paper writers'; regurgitating 'proforma' arguments/templates which should have been corrected long ago to reflect ACTUAL history of ZWICKY's ORDINARY DM hypothesis; AND of MUCH LATER 'exotic' DM fantasies posited/perpetuated by desperate/lazy HACK 'theorists', 'researchers' and 'paper-writers' driven by publish-or-perish/face-saving IMPERATIVES while NOT HAVING CLUE ONE regarding EITHER/BOTH the history OR the reality; for too long pretending/prognosticating about EXOTIC (fantasies) DM they've been trying but failing to find/explain for almost as long as same incestuous 'professional theorist' and 'publishing' crowd/system have been doing/failing for BB/Inflation etc fantasies.

So, you and ZWICKY ok now? :)
Benni
1 / 5 (6) Jan 24, 2018
So, you and ZWICKY ok now? :)


......with someone who thought rockets wouldn't work in outer space because there was no atmosphere for rocket exhaust to push against to create forward thrust? HaHahaha.........stop making me laugh, it's almost as bad as RNP who can't put up a sensible DE that also made me almost want to laugh because he was so inept at it, he probably copied the right hand side of that thing from a Zwicky featured website.
Bart_A
1 / 5 (4) Jan 24, 2018
Anti, you are playing on words. DM is a "theory" according to the dictionary definition of "Abstract reasoning; speculation; an assumption based on limited information or knowledge; a conjecture."

That's really all it is.

arcmetal
5 / 5 (1) Jan 25, 2018
When the floor falls off this theory, ....

Are you assuming here that the theory must necessarily be wrong? If so, how can you rationally know this? Are you a qualified cosmologist or at least a qualified physicist? Have you got an alternative theory that has passed scientific peer preview? What makes you think you know better than other people smarter than you that have researched it for many years when you haven't? I for one don't assume I must know better than other people smarter than me (about something) who have properly researched it when I haven't. I think dark matter may or may not exist and its too early to tell.

I don't need to be a "qualified" mechanic to know that driving a car without air in the tires is not a good idea.
antialias_physorg
4.4 / 5 (7) Jan 25, 2018
Anti, you are playing on words. DM is a "theory" according to the dictionary definition of "Abstract reasoning; speculation; an assumption based on limited information or knowledge; a conjecture."

Then you will have no problem pointing to the specific theory that is called 'dark matter', won't you? I mean the *one* dark matter theory that is called "Dark Matter", is published and makes a prediction.

(Hint: you can't)
Benni
1 / 5 (5) Jan 25, 2018
Anti, you are playing on words. DM is a "theory" according to the dictionary definition of "Abstract reasoning; speculation; an assumption based on limited information or knowledge; a conjecture."

Then you will have no problem pointing to the specific theory that is called 'dark matter', won't you? I mean the *one* dark matter theory that is called "Dark Matter", is published and makes a prediction.

(Hint: you can't)


anti........just curious, remember when to told us that you sent your resume to that retired firefighter Stumpy, did he ever find you a job?
antialias_physorg
4.1 / 5 (9) Jan 25, 2018
anti........just curious, remember when to told us that you sent your resume to that retired firefighter Stumpy, did he ever find you a job?

Erm whut? What are you talking about? I sent him a paper about my work.
(and I do have a very nice job - so what on Earth are you on about?)

I mean it's sorta funny that you think most basic skills are somehow 'advanced' or that anyone would take you for an engineer....but now you're letting your Alzheimer show again. Keep up with the program.

Benni
1 / 5 (5) Jan 25, 2018
I mean it's sorta funny that you think most basic skills are somehow 'advanced' or that anyone would take you for an engineer....but now you're letting your Alzheimer show again. Keep up with the program.


When YOU trying passing off Neutron Degeneracy Pressure as an example of the Pauli Exclusion Principle, that's as clear an example as can exist that "you're letting your Alzheimer show again".

Got anymore name calling tirades that you think are a suitable substitute for Nuclear Physics?
antialias_physorg
4.5 / 5 (8) Jan 25, 2018
When YOU trying passing off Neutron Degeneracy Pressure as an example of the Pauli Exclusion Principle

Erm whut? Fantasizing again?

Let's see. From:
https://en.wikipe...e_matter


In a quantum mechanical description, free particles limited to a finite volume may take only a discrete set of energies, called quantum states. The Pauli exclusion principle prevents identical fermions from occupying the same quantum state. At lowest total energy (when the thermal energy of the particles is negligible), all the lowest energy quantum states are filled. This state is referred to as full degeneracy. he pressure (called degeneracy pressure or Fermi pressure) remains nonzero even at absolute zero temperature"


Does that spell it out for you?
Benni
1 / 5 (5) Jan 25, 2018
When YOU trying passing off Neutron Degeneracy Pressure as an example of the Pauli Exclusion Principle

Erm whut? Fantasizing again?
In a quantum mechanical description, free particles limited to a finite volume may take only a discrete set of energies, called quantum states. The Pauli exclusion principle prevents identical fermions from occupying the same quantum state. At lowest total energy (when the thermal energy of the particles is negligible), all the lowest energy quantum states are filled. This state is referred to as full degeneracy. he pressure (called degeneracy pressure or Fermi pressure) remains nonzero even at absolute zero temperature"


Does that spell it out for you?


Yep, that you continue suffering from:
"you're letting your Alzheimer show again"

Captain Stumpy
5 / 5 (4) Jan 25, 2018
@idiot Alzheimers troll benji
did he ever find you a job?
1- he has a kick *ss job already

2- did you ever learn how to actually do differential equations?

considering there is absolutely no proof whatsoever (anywhere) that you're capable of doing DE's of any kind, and there is proof on PO alone that you're inept at even basic math...

(partial list of those epic fails located here: https://phys.org/...ars.html )

it isn't a "name calling tirade" to argue that you're inept or to point out your failures
- it is a proven fact

antialias_physorg
4 / 5 (8) Jan 25, 2018

Yep, that you continue suffering from: ...


Well, can't help you if you don't know stuff that would be super-basic knowledge for an electrical engineer (and even more basic for someone supposedly specializing in nuclear engineering).

If you can't even comprehend a wikipedia article: what can you comprehend? (and don't say PDEs - we already know you have no clue about those)
Benni
1 / 5 (6) Jan 25, 2018
Yep, that you continue suffering from: ...


Well, can't help you if you don't know stuff that would be super-basic knowledge for an electrical engineer (and even more basic for someone supposedly specializing in nuclear engineering).

If you can't even comprehend a wikipedia article: what can you comprehend? (and don't say PDEs - we already know you have no clue about those)


You & Stubby need to find different retirement careers........it's a good thing you don't need to walk more than two blocks to the grocery store, the mathematical logistics beyond that would confound you.
RealityCheck
1 / 5 (4) Jan 25, 2018
@antialias, @Benni.

REMINDER: There is NO SUCH THING as a 'stable' Neutron. A Neutron MAY 'decay' at all PRECISELY BECAUSE IT IS UN-stable (as compared to Proton, which is the ONLY 'nucleon' that IS stable).

CONSIDER: Even in the nucleus of atom, a Neutron is ALWAYS in 'unstable equilibrium'; as Proton(s) provide the opportunity for 'mutual exchange' of negative (electron) charge which transiently 'changes' adjacent Proton to 'Neutron-like state' while allowing adjacent Neutron to transiently 'convert' to a Proton-like state, back and forth, so stabilizing that nucleus.

IMAGERY: Think of it as TWO (or more, as the case may be) PROTONS 'juggling' a 'hot potato' (electron) between them so that EITHER ONE may become a 'Neutron' FLEETINGLY before 'handing back' the 'hot potato' (electron) to the OTHER Proton, which, in its turn, fleetingly becomes the 'Neutron'.

See? Whether 'dynamically paired' (transient equilibrium in a nucleus), or 'free', a Neutron is NEVER 'stable'. :)
RealityCheck
1 / 5 (4) Jan 25, 2018
@Benni.
So DM is ORDINARY and BEING DETECTED, as ZWICKY PREDICTED!.......So, you and ZWICKY ok now? :)
with someone who thought rockets wouldn't work in outer space because there was no atmosphere for rocket exhaust to push against to create forward thrust? HaHahaha.
Please stick to the subject/issue we were discussing, mate. I only pointed out the ACTUAL history/facts re Zwicky's ORIGINAL prediction re THEN UNDETECTABLE MATTER, ie ORDINARY 'dark' STUFF and NOT EXOTIC 'fantasy stuff' dreamed up by OTHERS since then. OK? :)

ps: While it is off-topic re our discourse on DM, and does not change the facts re his posit/prediction re DM, I am still intrigued re the 'rocket' claims you mentioned as coming from Zwicky. But I am still very busy, so can you please save me some precious time by posting a link to where he is quoted (at the time) saying what you just attributed to him? Thanks. Gotta go; back tomorrow. :)
Benni
1 / 5 (5) Jan 25, 2018
See? Whether 'dynamically paired' (transient equilibrium in a nucleus), or 'free', a Neutron is NEVER 'stable'


What you state is true, but the neophytes living here believe an absolutely preposterous concept labeled NEUTRON DEGENERACY PRESSURE is actually REAL, they actually think junk science labels like this is REAL. They don't know the term NEUTRON DEGENERACY PRESSURE is totally made up by Cosmology to cover their tracks for things that have already been proven not to exist inside the Hadron Collider.

Believing their silly putty dust can actually exist, these funny farm pop-sci junkies think if enough pressure is added to a mix of free neutrons that they won't decay, or that the onset of decay can be negated in accordance by some unstated quantity of PRESSURE, then invoke Pauli Exclusion Principle and VOILA, they get NDP. The face of it is completely laughable & has only ENTERTAINMENT VALUE., but we do need those who are willing to be OUR entertainment.
Benni
1 / 5 (4) Jan 25, 2018
Believing their silly putty dust can actually exist, these funny farm pop-sci junkies think if enough pressure is added to a mix of free neutrons that they won't decay,


Ooooops, I forgot.........WhyGuy may know about a neutron storage technique using his gas cylinders in his metal bending studio.

THAT"S IT !!!!!!!!! WhyGuy, have your pressure gas cylinder suppliers replace the current nitrous oxide with neutrons, and just pressurize the bottles to a safe limit, and VOILA yet again, NEUTRON DEGENERACY, neutrons under pressure will never decay, well, for at least a few million years.
Merrit
not rated yet Jan 26, 2018
I think scientists biggest mistake is believing they can directly detect DM particles regardless if they actually exist or not. The ability of DM particles to directly interact with ordinary matter greatly changes how it would distribute itself throughout the universe. The scientists should be using what they know of the predicted DM concentrations to determine to what extent they can interact with themselves and ordinary matter before they simply assume they can. The fact we have not yet directly detected them likely indicates either we can't or they don't exist.
Merrit
not rated yet Jan 26, 2018
The only thing we know for certain is that our models do not match reality for things such as galaxy rotation. While additional invisible matter could solve the issue it is a fallacy to believe the issue is necessarily a disconnect between the amount of matter and rotation curves. Our conclusion is based on many intrinsic assumptions that just might not hold at galactic scale. This whole DM and DE thing really just show our model has an issue and scientists at this point should be focusing on where we could be misunderstandings things or missing emergent phenomenon.
IwinUlose
3.2 / 5 (9) Jan 26, 2018
overage Trekkie culture living here on this site, right Schneibo?


and there you go Mr Freelance Journalist, as usual directly off the plantation of Funny Farm Science.

Hey, do you know what a Differential Equation looks like?


coming from a Jounalist, what else could be expected.


stop making me laugh, it's almost as bad as RNP who can't put up a sensible DE that also made me almost want to laugh because he was so inept at it,


remember when to told us that you sent your resume to that retired firefighter Stumpy


Ooooops, I forgot.........WhyGuy may know about a neutron storage technique using his gas cylinders in his metal bending studio.


I'm sorry for whatever happened to you. Look what it did to you :/
Benni
1.7 / 5 (6) Jan 26, 2018
I'm sorry for whatever happened to you. Look what it did to you


I come to the Comments section for the entertainment value of making fun of funny farm science of issues like: neutron degeneracy, infinite forces of gravity on a finite stellar mass, a Universe in which dark energy substitutes for entropy, neopphytes subjecting an electro-magnetic wave to kinetic energy, DM cosmic fairy dust,..............and lately wondering why so many experts like Stumpo & RNP can't do DIFFERENTIAL EQUATIONS.

So, tell us, why are you here?

antialias_physorg
4.6 / 5 (9) Jan 26, 2018
There is NO SUCH THING as a 'stable' Neutron. A Neutron MAY 'decay' at all PRECISELY BECAUSE IT IS UN-stable

You are missing quit a bit of the funadmentals here.
To summarize: Neutrons and protons (and electrons) are fermions. Fermions obey the Pauli exclusion principle (which means that you cannot have the same quantum state occupied by two of these) . In a neutron star stuff is so close together that all quantum states are occupied.

*Free* neutrons can decay because there is lots of free quantum states for the resulting proton and electron to occupy. In a neutron star there is no such freedom.
Benni
1.7 / 5 (6) Jan 27, 2018
You are missing quit a bit of the funadmentals here.
To summarize: Neutrons and protons (and electrons) are fermions. Fermions obey the Pauli exclusion principle (which means that you cannot have the same quantum state occupied by two of these) . In a neutron star stuff is so close together that all quantum states are occupied.
.........and you as a Biologist have zero comprehension of what you just Copied & Pasted from WikiPedia.

Nuclear Shells are MODELS to which theorists apply Pauli Exclusion Principle, in other words: Let's be whimsical.

Biologists like you should not be trying this.
RNP
3.8 / 5 (10) Jan 27, 2018
@antialias_physorg
It really is pointless trying to talk to this guy, isn't it? He clearly understands nothing and yet expects others to believe he knows better than everybody else that posts here on phys,org (I note that nobody ever agrees with his nonsense), Even more laughably, he claims to know better than the authors of the papers he prattles on about. I used to argue with him. Now, I just prod him occasionally to provoke another of his risible comments and let everyone have a laugh,
Da Schneib
3.7 / 5 (3) Jan 27, 2018
So, looks like there's another way to check the characteristics of whatever "dark matter" is a placeholder for. Apparently DM and stars can recruit one another and their orbital mechanics will settle down and become common. It's not clear from this article whether this is by gravitational effects or some sort of friction that slows the stars down and speeds the DM up; I think I'll have a look at the paper if I can get it.
Da Schneib
4.2 / 5 (5) Jan 27, 2018
The paper is available on arXiv. https://arxiv.org...04.04499

Studying it now.
Da Schneib
4.2 / 5 (5) Jan 27, 2018
Yeah, this one is pretty solid. It depends on the virial theorem, and upon virialization which happens over time as various things interact with one another. It is not dependent upon quantum scattering; the use of the term "scattering" appears to be limited to gravitational effects.

Finding that models that match real observations follow these kinematics would strongly indicate that interactions between DM and VM (metal-poor stars from small galaxies absorbed by the Milky Way) are almost or completely gravitational.
Da Schneib
4.4 / 5 (7) Jan 27, 2018
@Lenni, just a reminder:

-m'' + m'n' - m'² - 2m'/r = 0
m'' + m'² - m'n' - 2m'/r = 0
e⁻²ⁿ (1 + m'r - n'r) - 1 = 0
R₂₂ sin² ϕ = 0
Source: http://www.etsu.e...esis.pdf

Anytime you want to give an answer you are free to do so. You never have, and that says everything there is necessary to know about your knowledge. And here, you have nothing to present but knowledge.

Oh and BTW @Lennitheliar, you might get a better response if you didn't make up names for people you don't like. I call you @Lenni because you can't do so. Just so that's clear.
antialias_physorg
4.5 / 5 (8) Jan 27, 2018
It really is pointless trying to talk to this guy, isn't it? He clearly understands nothing and yet expects others to believe he knows better than everybody else

Yeah, but it highlights (to the casual reader of these comments) whether they need to bother with his posts elsewhere.

I'm not doing this for his education (there's no way i'm gonna start up a kindergarten-course for him, here) . I'm doing it for the fun of it and - possibly - the benefit of others.
RealityCheck
1 / 5 (4) Jan 27, 2018
@antialias.
There is NO SUCH THING as a 'stable' Neutron. A Neutron MAY 'decay' at all PRECISELY BECAUSE IT IS UN-stable
You are missing quit a bit of the fundamentals here.
...

*Free* neutrons can decay because there is lots of free quantum states for the resulting proton and electron to occupy. In a neutron star there is no such freedom.
REMINDER: Abstract mathematical models do not guarantee the reality is as abstractly modeled. :)

CONSIDER: The ultra-high-energy 'environment' and the various 'levels' of 'pressure containment' at various radial 'altitude' layers from central core to surface layers of NS. The extremely energetic QUANTUM dynamics, and the differing 'containment' conditions would produce various forms of PLASMA states/behaviour, ranging from QUARK-GLUON type plasmas to PROTON-ELECTRON type, with varying temporal/radial 'neutralization/reforming' etc.

See? The naive/simplistic 'abstract' modeling you are working from is NOT reality, mate. :)
Da Schneib
4.3 / 5 (6) Jan 27, 2018
@RC, carbon-12 doesn't decay. It has neutrons in it.

Just sayin'.
RealityCheck
1 / 5 (4) Jan 27, 2018
@Da Schneib.
@RC, carbon-12 doesn't decay. It has neutrons in it.

Just sayin'.
Yes, I already pointed out that the (IMAGERY) 'hot potato' (electron) dynamical/constant 'back and forth' exchange between protons (thus either proton transiently and in turn fleetingly behaves as 'the neutron') can make such complex atomic nuclei stable. It is the 'stability' (or rather the IN-stability) of the NEuron itself that was the point, not the atomic nuclei stability as such. If you go back and re-read my relevant post you will see that you may somehow have conflated the two when making your above remark which is besides the point/reminder I made re Neutron 'instability'.

Thanks for your polite, on-science response anyway, mate. Happy and safe New Year to you and yours, DS. :)
Da Schneib
4.3 / 5 (6) Jan 27, 2018
If you want to look at it in that simplistic manner without understanding the underlying mechanics, @RC, that's your privilege I suppose.
RealityCheck
1 / 5 (4) Jan 27, 2018
@Da Schneib.
If you want to look at it in that simplistic manner without understanding the underlying mechanics,....
I clearly stated it was an IMAGERY to aid understanding of the dynamical nature of what is actually happening on the quantum level between 'nucleon' protons when there is an 'extra' negative charge in the atomic NUCLEUS dynamics. That extra electron (the imagery of 'hot potato') is NOT bound to any ONE proton, but at least TWO...hence the ATOMIC NUCLEUS stability via the exchange which does not 'bind' that 'extra' electron to either proton long enough to make one a 'neutron' except as a transient 'intermediate state' which is practically IMMEDIATELY REVERSED by 'transfer' of that 'hot potato' (electron) to the 'other' proton; and and so on, back and forth.

As for 'simplistic', it is no more simplistic than current QM 'abstractions' in the maths modeling.

Cheers; and thanks again for your polite, on-science responses, DS. :)
Da Schneib
4 / 5 (4) Jan 27, 2018
There aren't any electrons in the nucleus, @RC. At a high level one can model it as pion exchange; at a low level, what's really going on is quarks exchanging gluons. It's probably also improper to talk about neutrons and protons in the nucleus since they have only evanescent existence as such and over such brief periods and distances the quarks that make them up are asymptotically free.
RealityCheck
1 / 5 (3) Jan 27, 2018
@Da Schneib.
There aren't any electrons in the nucleus, @RC. At a high level one can model it as pion exchange; at a low level, what's really going on is quarks exchanging gluons. It's probably also improper to talk about neutrons and protons in the nucleus since they have only evanescent existence as such and over such brief periods and distances the quarks that make them up are asymptotically free.
Yes! Exactly, DS!

That's why I posted the two-pronged reminder/imagery; the FIRST prong reminded @antialias and @Benni WHY there is NO such thing as a 'stable' Neutron EVER; and the SECOND prong reminded @antialias WHY there is NO such thing as 'stable' NEUTRON as such either in atom nuclei OR in NS interior dynamics/states.

Hence my imagery of 'hot potato' exchanges, be it electron, pion or other form (I only kept to the electron for ease of explanation/imagery); and also hence why I pointed out the QUARK-GLUN PLASMA states/dynamics within NS interior.

Thanks, DS! :)
Da Schneib
4.3 / 5 (6) Jan 27, 2018
Any statement about what happens inside a neutron star is speculation or at best hypothesis. Since we don't have one to examine we are limited in what we can figure out about it.
RealityCheck
1 / 5 (3) Jan 27, 2018
@Da Schneib.
Any statement about what happens inside a neutron star is speculation or at best hypothesis. Since we don't have one to examine we are limited in what we can figure out about it.
Again, yes! Exactly, DS! Which is why @Benni (and others, including me) have baulked at accepting the longstanding characterization of NS INTERIOR being 'mainly composed' of 'Neutrons'; and even more objectionable, being composed of allegedly 'stable Neutrons' at that!

In any case, your/my view of NS interior being more dynamic, in 'flux', with many energy forms/states of plasmas, ranging from Quark-Gluon to more transient proton-neutron 'intermediate' evanescent 'plasma' states/dynamics, is, at least at this stage of QM understandings, the most likely/tenable reality/hypothesis of what is/going on in NS astronomical objects/features.

Again, DS, thanks for your polite, helpful, on-science contribution to the issue re Neutron IN-stability in ATOMIC nuclei AND (so called) NSs! :)
Da Schneib
4 / 5 (4) Jan 27, 2018
the longstanding characterization of NS INTERIOR being 'mainly composed' of 'Neutrons'; and even more objectionable, being composed of allegedly 'stable Neutrons' at that!
I'm not familiar with this characterization as a matter of theory, @RC. It sounds like pop science to me.
RealityCheck
1 / 5 (3) Jan 27, 2018
@Da Schneib.
the longstanding characterization of NS INTERIOR being 'mainly composed' of 'Neutrons'; and even more objectionable, being composed of allegedly 'stable Neutrons' at that!
I'm not familiar with this characterization as a matter of theory, @RC. It sounds like pop science to me.
And yet again, yes! Exactly, DS! And ultra naive/simplistic 'pop science' view at that!

Which is why it has been so intriguing as to why certain posters here attacked @Benni when he pointed that out in response to certain posters/mainstream 'theorists' believing in 'Neutron stability' etc within Atom nuclei or in NSs?

I suppose 'personal animosities' keep getting in the way of polite and objective scientific/logical discourse sometimes. But I trust that this new year will see that sort of thing wane. I hope!

Cheers; thanks for your continuing polite, on science, responses. They have been very helpful to all objective observers I suspect.

Gotta go. Thanks again, DS. :)
Da Schneib
4.4 / 5 (7) Jan 27, 2018
But the problem is, you aren't addressing the point which is that you say:
Which is why @Benni (and others, including me) have baulked at accepting the longstanding characterization of NS INTERIOR being 'mainly composed' of 'Neutrons';
but then I point out
I'm not familiar with this characterization as a matter of theory, @RC.
and you respond without addressing this point. You can't mischaracterize the mainstream scientific view without making a strawman argument. It's basic logic.
RealityCheck
1 / 5 (4) Jan 27, 2018
@Da Schneib. Sorry I had to log out in a hurry and didn't have a chance to respond right away to this from you:
But the problem is, you aren't addressing the point which is that you say:
Which is why @Benni (and others, including me) have baulked at accepting the longstanding characterization of NS INTERIOR being 'mainly composed' of 'Neutrons';
but then I point out
I'm not familiar with this characterization as a matter of theory, @RC.
and you respond without addressing this point. You can't mischaracterize the mainstream scientific view without making a strawman argument. It's basic logic.
Wasn't it the mainstream professional theoretical/observational astrophysicist/astronomer scientific community that called it a NEUTRON star? And hasn't that same community encouraged and allowed 'science' Paper-Writers, Popularizers and Journalists to perpetuate that 'characterization' AS a NEUTRON stellar object/feature since they first coined that name/label? :)
Captain Stumpy
5 / 5 (5) Jan 27, 2018
It really is pointless trying to talk to this guy, isn't it? He clearly understands nothing and yet expects others to believe he knows better than everybody else

Yeah, but it highlights (to the casual reader of these comments) whether they need to bother with his posts elsewhere
As I've repeatedly stated in various places, there is a good reason to debunk idiots posting pseudoscience like benji and rc
https://www.youtu...EwjBXlZE

regardless of the availability of information it seems people are just too lazy to actually look up facts, so idiots posting pseudoscience or blatant lies can cause said stupidity to proliferate

you don't have to refute every post (because some posters like rc or zeph are verbose)
Da Schneib
4.2 / 5 (5) Jan 28, 2018
@RC, you mean several decades ago? At that time quarks had not been shown to exist, and it was believed that the only thing keeping the star from collapsing into a black hole was neutron degeneracy pressure. Since then we've found out a lot more. The name stuck and there you have it. Kinda like "dark matter."
Benni
1.8 / 5 (5) Jan 28, 2018
But the problem is, you aren't addressing the point which is that you say:


Which is why @Benni (and others, including me) have baulked at accepting the longstanding characterization of NS INTERIOR being 'mainly composed' of 'Neutrons'


but then I point out


I'm not familiar with this characterization as a matter of theory,@RC


and you respond without addressing this point.You can't mischaracterize the mainstream scientific view without making a strawman argument. It's basic logic.


Hey, schneibo, it is not a "strawman argument" to point out something you, RNP, a_p, etc, never before knew until I pointed it out to you:

FREE NEUTRONS HAVE A 15 MINUTE DECAY RATE

This sent the whole bunch of you neophytes who never saw a Differential Equation you could solve, into absolute apoplexy.

Next, you apoplectic neophytes living here, head over to WikiPedia & start reading about NEUTRON SHELL MODELS as if such a model exists.
Benni
1 / 5 (4) Jan 28, 2018
..............
Next, you apoplectic neophytes living here, head over to WikiPedia & start reading about NEUTRON SHELL MODELS as if such a model exists.


When whimsical Pop-Sci Cosmologists attempt to create NEUTRON STARS via collapsing Super Nova, they forget that a Super Nova endures for days, weeks & even years before COLLAPSE. In the meantime NEUTRONS, and most everything else is being blown into space at relativistic speed, and most especially the 3rd particle required for the makeup of a neutron, a neutrino.

Within seconds of a Super Nova neutrinos will be blown so far away from the point source of a novae explosion that they will be gravitationally unrecoverable due to their velocity just under light speed. It won't matter what will be the available quantity protons & electrons gravitationally held within the local mass, but without that neutrino a so called DEGENERATE PRESSURE can never create a NEUTRON, hence no neutron star.

Da Schneib
4.2 / 5 (5) Jan 28, 2018
Hey, schneibo, it is not a "strawman argument" to point out something you, RNP, a_p, etc, never before knew until I pointed it out to you:

FREE NEUTRONS HAVE A 15 MINUTE DECAY RATE
@LennitheLiar lies again.

Why then did I point out that carbon-12 is stable?

Duh ummm.

Are you not believing in neutron stars this week? Do the Thunderdolts have another electricity explanation for them too?
Benni
1 / 5 (4) Jan 28, 2018
Schneibo.......you know so little about nuclear physics that you would confuse an atom, carbon-12, with a free neutron?

I know, next you're gonna argue carbon-12 is not an atom, right?

Or, are you gonna try the mockup model of a neutron as a shell with a nucleus at the center surrounded by a cloud with orbitals of something (?) equating it to the electron shell of an atom? OOOOOO, whoopy doooo, lots of funny farm science & magical numbers to work with now.

I'll tell ya, when that super nova goes bango, any free neutrons that are created are not gonna first head to some textbook you hold dear to find out what to do next. Those free neutrons won't have hours, days weeks, months and years while waiting for GRAVITATIONAL COLLAPSE before they decay, it'll be 15 minutes & you can't prove differently because it's been proven in the Hadron Collider this is what factually occurs.

Da Schneib
4 / 5 (4) Jan 28, 2018
This is silliness. Never mind.
Benni
1 / 5 (4) Jan 28, 2018
This is silliness. Never mind.


Yep, you lost the debate, again.

Da Schneib
5 / 5 (2) Jan 28, 2018
There isn't any debate when you lie. I don't know why you bother; it's not like you're fooling anyone.
IwinUlose
1 / 5 (2) Jan 29, 2018

So, tell us, why are you here?


This is where most of the good science news seems to end up; and the comments are like daytime television for people who like to read more than watch.
Merrit
not rated yet Jan 29, 2018
@benni not sure how a 15 minute half life of a free neutron matters in the least. First of all how many free neutrons do you think there will be after a supernova? Most of the matter should be in the forms of atoms. Secondly it doesn't matter if many neutrinos are given off. The needed neutrinos can be absorbed from elsewhere at a later point. Thirdly as DA has pointed out scientists do not believe neutron stars are comprised of only neutrons especially the interior.
TechnoCreed
5 / 5 (1) Jan 29, 2018
I am annoyed by people questionning the neutron star model or the r-process model when since they totally match with the observations allowed by GW170817. Some food for taught: r-process for heavy nuclei involves neutronic wind density of 10^24 neutrons/cm^3 to 10^28 neutrons/cm^3 (10^28 neutrons/cm^3 ~ 17kg/cm^3) and a free neutron to seed nucleus ratio superior to 100.

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