Stars Fueled by Dark Matter Could Hold Secrets to the Universe

Nov 03, 2009 By Lisa Zyga feature
Simulated view of a black hole in front of the Large Magellanic Cloud. Dark stars could grow to become much larger than normal stars, and might collapse to form the giant black holes in the centers of galaxies. Credit: Wikimedia Commons.

(PhysOrg.com) -- The first stars in the universe may have been very different from the stars we see today, yet they may hold clues to understanding some of the mysterious features of the universe. These "dark stars," first theorized in 2007, could grow to be much larger than modern stars, and would be powered by dark matter particles that annihilate inside them, rather than by nuclear fusion. In the early universe, dark stars would have emitted visible light like the Sun, but today their light would be redshifted into the infrared range by the time it reaches us, and so dark stars would be invisible to the naked eye.

Over the past two years, researchers have further investigated the properties of dark stars, as well as how these unusual stars may help scientists better understand , , and other astronomical features. In a new study, the group of scientists that originally theorized dark stars has presented a review of the research on dark stars and predicted future areas of research. Katherine Freese of the University of Michigan; Paolo Gondolo of the University of Utah; Peter Bodenheimer of the University of California, Santa Cruz; and Douglas Spolyar, currently with Fermilab, have published their results in a recent issue of the .

As the scientists explain, dark stars would represent a new phase of - the first phase, occurring just 200 million years after the big bang. At that time, dark matter densities in the early universe were higher than they are today, and the first stars are predicted to have formed in the middle of dark matter haloes (which are precursors to galaxies) as opposed to today’s stars that are scattered about the edges of a galaxy. According to the theory, these early stars grew larger by accreting mass from their surroundings, pulling in dark matter along with the surrounding gas.

Inside these stars, weakly interacting massive particles (WIMPs), a candidate for dark matter, could accumulate. Since WIMPs can be their own antiparticles, they could annihilate to produce a heat source. If the dark matter density was high enough, this heating would dominate over other heating (or cooling) mechanisms, such as . Compared with fusion, WIMP annihilation is a very efficient power source, so that only a small amount of dark matter is required to power the star.

“Dark stars are a natural consequence of WIMPs as dark matter particles ... although it took us a while to put the necessary ingredients together to realize this!” Freese told PhysOrg.com. “At the time we proposed these objects in 2007, we didn't realize that they are really stars in the sense of being hydrostatically stable objects that shine and produce visible light. Now that we have succeeded in finding the stellar structure of these objects, we understand their properties: they are giant puffy objects (like suns that extend out to the radius of the earth) and the light they produce looks a lot like that from the Sun. But they grow to become a thousand or even a million times as massive! These are our new results since we first began our research in this area.”

As the scientists explained, modern stars eventually burn up their hydrogen and transition into other star types on the main sequence diagram. On the other hand, dark stars can keep growing indefinitely, as long as they keep accreting dark matter from their surroundings. If not disturbed, these stars could potentially grow to be tens of thousands of times larger than the Sun. However, most dark stars would probably eventually stray from their locations at the centers of dark matter haloes. Their dark matter fuel would run out, so that the stars would start to collapse and eventually be powered by fusion from the stars’ normal hydrogen atoms, and finally collapse into black holes. The scientists calculated that dark stars have a lifetime of at least one million years, and perhaps billions of years; they might even still be around today.

The scientists predict that it should be possible to detect dark stars, either by detecting their light with upcoming telescopes, or by using neutrino telescopes to measure neutrinos from dark stars. Compared with conventional main sequence stars, dark stars that have run out of dark matter fuel and started using fusion would be much larger, cooler, and “puffier.” And while dark stars ultimately become black holes, the first stars in the traditional view (without dark matter) turn into supernova, giving the researchers a point of comparison.

“These supernova populate the universe with element abundances in very precise ratios (the ratio of even to odd elements is very precise),” Freese explained. “However, we predict that this doesn't happen in dark stars. So this distinction provides a measurable test of the two different scenarios. These element abundances should be measured in the next five years and then we'll know.”

By measuring the properties of dark stars with future instruments, scientists could discover detailed properties of dark matter. Since different produce different annihilation products, measurements could reveal information about the properties of dark matter, such as their mass, their annihilation mechanisms, etc. Freese also plans to investigate whether dark stars could become large enough to produce the giant black holes that are currently unexplainable.

“So far we have built up dark stars to 1,000 times the mass of the Sun,” she said. “But if they keep accumulating dark matter by capturing it from the surroundings, they can end up much larger: possibly even a million times as massive as the Sun. This is my immediate goal as far as research endeavors. Such supermassive objects were first proposed in the ‘60s by Fowler and Hoyle, but nobody knew how to make them. If this is right, it certainly helps explain the enormous black holes seen in the universe that nobody knows how to explain: when the supermassive stars die, they become black holes. There are billion-solar-mass black holes seen at basically the time the first galaxies formed, as well as the ones in centers of galaxies.”

More information: Katherine Freese, Peter Bodenheimer, Paolo Gondolo, and Douglas Spolyar. “Dark stars: a new study of the first stars in the .” New Journal of Physics 11 (2009) 105014.

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SincerelyTwo
4 / 5 (1) Nov 03, 2009
Just curious, is there a limit as to how intense the pull of gravity can be, caused by a body of mass? When a body of mass has sufficient gravity to prevent light from escaping, is that a limit or just a threshold which causes distinct effects? What I'm hoping to learn is if we have a measure of what the most powerful body of mass is known to date, determined by how powerful said object's pull of gravity is?

Is there any literature available which explores such extreme conditions based on the models we've been able to build with the physics we currently understand?
ruebi
2.3 / 5 (7) Nov 03, 2009
Is it not possible that the "Big Bang" was just the collision of two or more super-massive "dark stars". It is possible that we are that infinitesimal. That the entire universe known to us is no larger than the space between fusion reactions within our own sun comparably.
gopher65
4.3 / 5 (3) Nov 03, 2009
That was one of the better physorg.com articles (internally produced) that I've read. Grats.
pauldentler
1 / 5 (2) Nov 03, 2009
Just curious, is there a limit as to how intense the pull of gravity can be, caused by a body of mass? When a body of mass has sufficient gravity to prevent light from escaping, is that a limit or just a threshold which causes distinct effects? What I'm hoping to learn is if we have a measure of what the most powerful body of mass is known to date, determined by how powerful said object's pull of gravity is?

Your question sounds like: "Can gravity become such a strongly attractive force that it at some point can prevent it's own lines of force from escaping a body? For example, the effects gravitational lensing on flux fields of the electro-magnetic spectrum caused by the gravitational field of the sun.
AnotherNoName
5 / 5 (3) Nov 03, 2009
Is it not possible that the "Big Bang" was just the collision of two or more super-massive "dark stars". It is possible that we are that infinitesimal. That the entire universe known to us is no larger than the space between fusion reactions within our own sun comparably.


It is logically possible, in that we can conceive it. However, we would need evidence in support of such a proposition such that we are more justified in accepting the proposition than its negation.
RobertKLR
3 / 5 (6) Nov 03, 2009
Interesting article but if dark matter is real show me a chunk of it.
SincerelyTwo
Nov 03, 2009
This comment has been removed by a moderator.
yyz
4 / 5 (1) Nov 03, 2009
An interesting short 2008 paper on 'Dark Stars' (using DM) can be found here: http://arxiv.org/...44v1.pdf . The paper expands on some of the concepts mentioned in the above article.
nkalanaga
4.2 / 5 (6) Nov 03, 2009
No, there really isn't a limit to how massive an object can be, or how powerful it's gravity. Once the surface escape velocity exceeds the speed of light, it becomes a black hole, but it can still accrete mass, and its gravity will continue to increase.

The only "problem" is that gravity is inversely proportional to the square of the radius, while the observed radius of a black hole is proportional to the mass. Double the mass, and the radius doubles. In turn, the gravity decreases by the square of the radius (1/4) times the mass (2), so the "surface" gravity is half as strong if the mass doubles! At a significant distance from two black holes, assuming the same distance from the theoretical center for both, the gravity will be proportional to the mass, as with any object.

I have read, but don't know if it's true, that the radius of a black hole with the mass of the observed universe would equal the observed radius of the universe. If so, we live inside a black hole!
dirk_bruere
3.7 / 5 (9) Nov 03, 2009
Consider me to be a Dark Matter skeptic. All this appears to be building theories on top of theories, and there are indications that our most basic theories are wrong.
Alexa
2.5 / 5 (2) Nov 03, 2009
..Since WIMPs can be their own antiparticles, they could annihilate to produce a heat source..
This is what only gravitons are supposed to be - or not?
..the radius of a black hole with the mass of the observed universe would equal the observed radius of the universe. If so, we live inside a black hole..
Yes, and the lifespan of such black hole corresponds the age of observable Universe with Hawking radiation of wavelength, corresponding to wavelength of microwave background of our Universe (CMB). In this way, Universe is black hole, which we are observing from inside via CMB.
ler177
1 / 5 (1) Nov 03, 2009
Maybe giant dark matter stars turning into black holes has something to do with quasars?
MorituriMax
5 / 5 (1) Nov 03, 2009
Is it not possible that the "Big Bang" was just the collision of two or more super-massive "dark stars".


The main problem I see with that idea is that there would have to be an existing universe already which would contain, among other objects, these two stars. It would have to be old enough and populated densely enough for those two stars to have accreted enough matter to become large enough for them to collide with such violence. And then we are back again to the fact that there wouldn't be any need for a Big Bang since all of the above had already happened. But man that would be one massive supernova if or when it happened.
amcke001
5 / 5 (1) Nov 03, 2009
There were times when the electron was disbelieved and when the earth the center of the universe. The skeptics disbelieve because there are inadequate tools which bring the imperceptible to the human perception range. Science rumbles on creating tools, theories and experiments that bring the unknown into perception. Dark matter was labeled such because it is undetectable, but observed through interaction with other masses. At some point LHC will fire up and move steps closer towards perceiving dark matter.
Lets suppose dark matter was observed through the instruments at LHC, does that make it no longer dark and require a new name. Is realm of dark matter that which is left unknown and undetectable.
brant
3.7 / 5 (3) Nov 03, 2009
There were times when the electron was disbelieved and when the earth the center of the universe. The skeptics disbelieve because there are inadequate tools which bring the imperceptible to the human perception range. Science rumbles on creating tools, theories and experiments that bring the unknown into perception. Dark matter was labeled such because it is undetectable, but observed through interaction with other masses. At some point LHC will fire up and move steps closer towards perceiving dark matter.


There will be a day coming soon that says exactly the same thing about dark matter as you just said about all the other stuff.....
Its all very bad speculation. And its all more stuff piled on top of previous theories that cant explain new discoveries. There are many observations that are not explained by dark matter etc.
me2goodfoyou
not rated yet Nov 03, 2009
wait, so if light is the fastest thing in our universe, what happens when light enters a black hole? doesn't that mean that something has to be faster than light in order to trap it? can enough gravity fold light onto itself to maybe form dark matter? anyone have any info about gravity? I'm still confused about it. Does gravity travel like light, or is it simultaneous and instantaneous?
Alexa
1 / 5 (3) Nov 03, 2009
In aether theory gravitational waves are analogy of sound waves spreading through underwater, whereas light waves are surface waves, spreading along surfaces of quantum foam of density fluctuations, which is forming vacuum. This explains, why gravitational waves should be way, way faster, then the light and why we didn't observe them already - only background noise. Even Einstein didn't believe in gravitational waves very much. I presume, model of superluminal gravity should have some meaning in superstring and holographic theory, in which gravity is spreading through extradimensions (note that surface water model considers extradimensions, too).
jyro
1 / 5 (6) Nov 03, 2009
My idea, every sun has a blackhole at it's center providing fuel from another universe to fuel the Sun. When a sun collapses, a star is formed in the other universe as the black hole reverses
CyberRat
Nov 04, 2009
This comment has been removed by a moderator.
Alexa
3 / 5 (2) Nov 04, 2009
every sun has a blackhole at it's center
Nice approach - but such idea doesn't explain anything.
MorituriMax
not rated yet Nov 04, 2009
wait, so if light is the fastest thing in our universe, what happens when light enters a black hole? doesn't that mean that something has to be faster than light in order to trap it? can enough gravity fold light onto itself to maybe form dark matter? anyone have any info about gravity? I'm still confused about it. Does gravity travel like light, or is it simultaneous and instantaneous?


Light always travels in a straight line. Mass in space bends lights path through space (sigh.. think the classic dimple in a rubber sheet but in 3D), black holes bend it so much that it can't go by, sort of an eternal holding pattern as it spirals into the hole. Lots of particles trying to get into the limited event horizon crashes them into each other giving off lots of nasty energy.
Alexa
not rated yet Nov 04, 2009
.what happens when light enters a black hole..
I presume, it's dispersed by density fluctuations inside of black hole. Gravity field of black hole is behaving like glass sphere and it reflects light from inside by mechanism of total reflection. You can consider a mirror hall model of Universe in this connection.

http://physicswor...nt/23009
SincerelyTwo
not rated yet Nov 04, 2009
nkalanaga;

What you say is true but is there a limit on how dense a body of mass can be? An increase of mass doesn't necessarily mean an increase of radius, does it?

Which makes me wonder about another question, what is the force which causes a body of mass to compress itself, increasing its density? Is it gravity? If so, would something like the strong nuclear forces fight against gravity inferring on a possible limit in to how dense matter can be?

Lol, I might have to devote myself to studying physics for a hobby, I really want to know some of the answers to the state of nature in the most *extreme situations.
Yellowdart
1 / 5 (1) Nov 04, 2009
Dark matter was conceived in order to solve the acceleration of expansion problem. There wasnt enough mass needed to bind the universe over billions of years into its present state without something to counter act gravity.

It is in essence the phlogiston of space.

Until someone actually can measure dark matter/energy and find a star...your just as good as discussing warp factors from Star Trek...
DozerIAm
1 / 5 (2) Nov 04, 2009
Thank you Yellowdart and dirk_bruere and brandt - you beat me to the punch here. Dark Matter theory is a "best guess" to explain the gravitational effects we are seeing. It is very likely to be wrong and merely be an artifiact of our poor grasp of How Things Work. To postulate Dark Stars made up of Dark Matter - well that's fine for navel gazers but I sure hope my tax dollars aren't funding this sort of silliness.

And amcke001, maybe Dark Matter will eventually be proven to exist and we will roll merrily on to with our scientific progress, but in general science doesn't bet on long shots - it measures, hypothesises, proves, repeats. You seem dangerously close to treating it as a belief system rather than in interesting theory.
Royale
not rated yet Nov 04, 2009
Is it not possible that the "Big Bang" was just the collision of two or more super-massive "dark stars". It is possible that we are that infinitesimal. That the entire universe known to us is no larger than the space between fusion reactions within our own sun comparably.

I've always loved thinking about the universe in ways like this. Just a thought though, since we have evidence that our universe is expanding wouldn't it then be fission, not fusion? I prefer M-theory myself which is similar to what you're saying.
fcy
not rated yet Nov 04, 2009
nkalanaga;

What you say is true but is there a limit on how dense a body of mass can be? An increase of mass doesn't necessarily mean an increase of radius, does it?

Which makes me wonder about another question, what is the force which causes a body of mass to compress itself, increasing its density? Is it gravity? If so, would something like the strong nuclear forces fight against gravity inferring on a possible limit in to how dense matter can be?

Lol, I might have to devote myself to studying physics for a hobby, I really want to know some of the answers to the state of nature in the most *extreme situations.


Yes, it's the force of gravity that compresses a star. When you get beyond a certain point, you have a neutron star. What keeps it from contracting further is "degeneracy pressure," which is related to the Pauli Exclusion principle you might have learned about in chemistry. No two particles can occupy exactly the same quantum state.
nkalanaga
not rated yet Nov 04, 2009
The density of a black hole is a matter of semantics. The usual number is the density of the mass inside the event horizon, which decreases with increasing mass and radius. In theory, the density inside increases toward the "singularity" in the center, where it may (or may not) be infinite, if there really is a singularity there, which is also the subject of debate. But the only measureable density is that at the radius of the event horizon.

A stellar mass black hole is much smaller, and therefore denser, than even a neutron star. The measured density of a galactic mass black hole (in theory) would be considerably less.
kro
not rated yet Nov 04, 2009
so "infinite gravity" is a possibility?
Thrasymachus
5 / 5 (2) Nov 04, 2009
Let us suppose, for the sake of argument, that the theory of dark matter and dark energy are analogous to the theory of phlogiston. If so, then it is far from silly to determine the effects of dark matter/energy, and then seek those effects in experiment and observation. Doing just that with phlogiston lead to the correct theory of oxygen. If dark stars are a consequence of the existence of dark matter, and the presence of dark stars leads to unique effects, such as the creation and distribution of various elements differently than normal stars do it, then there are observations that can be made to verify or falsify the theory of dark matter. None of this is "silly" or a waste of taxpayer's dollars.
SincerelyTwo
not rated yet Nov 04, 2009
fcy;

Unless I misunderstood did you just mean to imply that mass cannot compress in to a denser state than what you find in a neutron star? How would you explain black holes then?

Maybe the Pauli Exclusion principle doesn't apply until much later, I wonder if its affects are even yet the significant factor to explain the state of even the most massive black holes today...

Can a value be calculated to determine at what mass enough gravity can manifest to force a body of mass to compress in to a state so dense that it is in fact the Pauli Exclusion principles at work which finally acts to prevent a body from becoming more dense?

And then can a diameter be determined from such a calculation, to figure out the area of such a mass?

If these two values could be found, it seems to me, we could begin to approximate the size of 'space' before or at the initial moment of the big bang, right? (I'm assuming at that moment all of the matter+energy+spacetime occupied the same area.)
nkalanaga
3.7 / 5 (3) Nov 04, 2009
Those are good questions, and I don't know the answers to them.

As for infinite density, that would be a "singularity", and the laws of physics as we know them won't work there. IN THEORY, a black hole has a singularity at its center, where the density is infinite. Most of what we "see" as a black hole, the volume inside the event horizon, is (theoretically) empty space, with the event horizon being where the escape velocity equals the speed of light.

The neutron star is the densest macroscopic state we can observe. Any denser and the Exclusion Principle fails, basically allowing the mass to fall into a subuniverse of its own. At that point the actual density of the matter is greater than in a neutron star, but all we can see are the gravitational effects at the event horizon.
Noumenon
4.8 / 5 (46) Nov 05, 2009
Good answers Nkalanaga. To continue with SincerelyTwo question,...

And at that mass (singularity), if light cannot escape, how can gravatational waves escape,...that is, if gravatational waves (or spacetime) can be infinitly curved at the singularity due to mass, would this impose an escape velocity upon it's own effects?

There's no quantum gravity theory yet, but is the graviton to escape, while light cannot?
nkalanaga
4 / 5 (4) Nov 05, 2009
That would be an argument against gravitons. If gravity is simply a bending of space-time, there isn't any problem, but it would seem that gravity waves would have a hard time escaping. On the other hand, if they're generated by the bending of space-time, rather than as a direct result of the mass, there wouldn't be a problem.

Most theories say gravity waves only occur around moving masses, so having the mass hidden inside an event horizon may not matter. The waves would appear to be generated at the horizon, as it moves, rather than at the singularity.

Since we haven't found gravitons, or reproducible gravity waves, yet, theories abound but facts are few.
Pogsquog
not rated yet Nov 06, 2009
A true singularity is impossible, because space would be infinitely stretched near it, so it would take an infinite amount of time for anything to ever reach it; hence working backwards, a point of infinite density can never form. Looking at it another way, if there were a true singularity, then another singularity colliding with it would reach infinite velocity, and hence must have had infinite gravitational potential energy in the first place, which implies infinite mass. Furthermore, infinity is such an ugly thing, mathematically, that I'm pretty sure our universe excludes it for aesthetic reasons.
Noumenon
4.8 / 5 (46) Nov 06, 2009
I always regarded singularities as the limit of GR rather than as an actual entity. Does GR predict actual singularities or rather does GR break down because of 'mathematical singularities'?
frajo
1 / 5 (1) Nov 06, 2009
I always regarded singularities as the limit of GR rather than as an actual entity. Does GR predict actual singularities or rather does GR break down because of 'mathematical singularities'?

IMHO there are no physical singularities (nor infinities). Mathematical singularities/infinities in theories of physics are indicators of incomplete theories.
And that's why we need strings.
SincerelyTwo
not rated yet Nov 06, 2009
Pauli Exclusion Principle describes that no identical fermions may occupy the same quantum state. The force which manifests at high enough density as a consequence is described as Electron Degeneracy Pressure.

http://en.wikiped...pressure

A result of continued pressure on a body of mass, fighting against EDP is Degenerate Matter.

http://en.wikiped...e_matter

Where it follows that;

"At densities greater than those supported by any degeneracy, gravity causes the matter to collapse into a point of zero volume. As far as is known today, no degeneracy state can exist within the Schwarzschild radius of a black hole, thus all its energy (mass) will be located in an infinitely dense singularity."
SincerelyTwo
not rated yet Nov 06, 2009
Continued; (ran past the char limit in previous comment.)

I think I'm understanding now why our current understanding of physics melts away in these extreme situations. - It literally melts away, that's amazing... Lol.

Good stuff! That was a lot of cool stuff to read in to. :] And I guess I might have answer my question above, no such diameter can be calculated leading to any idea of what 'size' the universe was at it's birth... it... literally came out of nothing? or it flooded through some kind of 'pinch' or ... something... hrm.... /wanders-off-aimlessly.

Frajo; does string theory off alternatives to what I've posted just now? Just curious...
NeilFarbstein
not rated yet Nov 06, 2009
Physicists have said for a long time that matter falling into black holes at their event horizons will annihilate and about 30% of their mass will be changed to energy.
frajo
1 / 5 (1) Nov 07, 2009
Nobody knows what's happening inside (the event horizon of) a BH. Thus we are free to speculate. But don't forget that GR doesn't know about Planck scales and Heisenberg uncertainties.
Frajo; does string theory off alternatives to what I've posted just now? Just curious...

String theory offers a lot of alternatives. My pet cosmology, the ekpyrotic/cyclic model is partly based on M-theory and does away with the notion of a BigBang singularity in a very elegant way. Unfortunately string theory is not established yet and has difficulties of its own.
A nice string intro: http://www.sukido...dex.html
Steinhardt's Princeton page: http://wwwphy.pri...~steinh/
benrot
not rated yet Nov 08, 2009
And if the BB was the gathering of anti-matter,emitted by dark matter, just like the enormous mas of floating waste in the middle of the Pacific Ocean, if this holds we are then anti-anti-matter!OR the BB was the critical mass of several Dark Masses?
DozerIAm
not rated yet Nov 09, 2009
I'm looking forward to seeing where MOND (Modified Theory of Newtonian Dynamics) goes. Give it another 50 years of tweaking and observations, it may give "dark matter" theories a run for their money.
NeilFarbstein
not rated yet Nov 09, 2009
I'm looking forward to seeing where MOND (Modified Theory of Newtonian Dynamics) goes. Give it another 50 years of tweaking and observations, it may give "dark matter" theories a run for their money.


Its defintely worth watching. What developments have you observed?
Foolish1
5 / 5 (1) Nov 13, 2009
Dark matter was conceived in order to solve the acceleration of expansion problem.

Until someone actually can measure dark matter/energy and find a star...your just as good as discussing warp factors from Star Trek...


FWIW dark matter and dark energy are entirely different concepts. They just share the "dark" name both being embarrassingly huge unsolved questions.

Dark energy is hubble expansion. Dark matter is stuff that does not appear to emit EM radiation and thus its existance can only be inferred by careful examination of gravitational interaction between things that can be seen.
NeilFarbstein
not rated yet Nov 13, 2009
I still think dark matter is ordinary matter. Dark objects that can be observed yet. Its possible that black holes are causing a lot of the gravitational discrepancy and bizarre readings. Almost everybody thinks black holes are real.
Possibly there's a reason why the dark matter is located where it is, outside the main parts of the galaxies. There ten times as much dark matter as visible matter. Can there be a reason that stars are rare in the outer zones where dark matter seems to be lurking? Electrostatic dispersal of dust particles? Who knows?

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