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Dark Matter Stars in the Early Universe?
OriginalArlen writes "UniverseToday reports new research which suggests dark matter could have condensed to form 'dark stars' in the early universe. These stars would have been very massive and burned very slowly, fueled by non-fusion reactions, they could still be with us. Astronomers hope to better constrain theories of early galaxy and star formation with observations of gravitational lensing events caused by these ghosts of the primordial universe."
Of course, that's where all of our packing material comes from.
Thank God for evolution.
"Nothing for you to see here. Please move along."
Indeed.
Hmm... what if we discover a star like the one Asimov described in Nemesis? Yes, I know it wasn't a dark matter star, but they didn't see it, either.
So I guess John Carpenter created the universe? http://imdb.com/title/tt0069945/
The Grateful Dead predicted the existence of Dark Stars about 30 years ago.
TFA brings up a good point, all this dark matter had to have condensed into big star-like masses and should still be around but it wouldn't just be pure dark matter there would be hydrogen and helium too and on the other hand stars like our sun should have dark matter in them too so where is it? if this dark matter is indeed doiung what they say why the heck heven't we detected it in some way?
Sigs are too short to say anything truly profound so read the above post instead.
The whole article sounds like a solution in search of a problem. It talks about "Dark Matter" as though the mysterious substance's properties were well-defined, even going as far as positing stars fuelled by "dark matter annihilation, instead of nuclear fusion". And then TFA says "If these dark stars are stable enough, its possible that they could still exist today".
I propose that dark matter is actually composed of jellybeans and M&M's, and that the first massive objects were stars fuelled by the crushing force of the crunchy shells of the M&Ms piercing the relatively soft outer coating of the jellybeans. Gravitational separation eventually turned the masses into giant Cadbury Creme Eggs.
Other than being completely silly, am I making any fewer wild guesses than the Dark Matter Annihilation folks?
Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
The bastard children of Dark Helmet and Lone Star?
Best Slashdot Co
Dark Star crashes...pouring it's light into ashes...reason tatters...the forces tear loose from the axis...
Just wondering but if they are are massive and burn slowly wouldn't they tend to collapse into black holes? If they don't put out enough heat to counter their gravitational field they should collapse. If so they may be the cores of the super massive black holes at the center of many galaxies. Just and idea since there where no numbers given in the article.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
On \. OriginalArlen reports the news. I look at the linked website, called Universe Today and I see that there is one "publisher" by the name of Fraser Cain. Following the link there, finally, I get to the article on the arxiv, the definitive source of new physics papers. So to get to the source, it takes three jumps. So what has Fraser Cain done for us? Watered down the content? Couldn't OriginalArlen read the article and write a gist himself/herself? Or is Fraser Cain the same person as OriginalArlen? Reading the original article, I find "some" correlation on what ends up on \. and what is in the article. Or is this not the point? If I had to write a review for this article, I would have said that the last sentence of the abstract is what is most important: "A ..star .. detectable via annihilation products (gamma-rays, neutrinos, anti-matter) possibly in combination with hydrogen lines."
The brilliant thing about this article is that these theorists are cooking up something that is actually detectable! Something that can be tested and hopefully will! *Finally* congrats to Douglas Spolyar, Katherine Freese and Paolo Gondolo, who *wrote* the article. (No, I dont know any of them. But isn't it time we cited those whose ideas we regurgitate?)
Here is the PDF: Dark matter and the first stars: a new phase of stellar evolution
Here is the abstract:
Ok, so say you are not a physicist, you can still read the article. It may have equations, but it is still English: http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.0521 v1.pdf
The authors say: "The nature of the cold dark matter in the universe is as yet unknown. Weakly Interacting Massive Particles (WIMPs) are possibly the strongest candidates, as WIMPs that were in thermodynamic equilibrium in the early universe automatically provide the appropriate relic abundance to give the observed matter density. More- over, WIMPs have a natural origin in particle physics, e.g. neutralinos in supersymmetric models are excellent DM candidates. [..]T he details of the interactions and masses of the neutralinos depend on a large number of model parameters. In the minimal supergravity model, experimental and observational bounds restrict the neutralino mass m to 50 GeV-2 TeV, while the annihilation cross section v lies within an order of magnitude of h vi = 3 × 10^-26cm3/sec (except at the low end of the mass range where it could be several orders of magnitude smaller). "
So the authors make it clear that they are working under a set of assumptions, which are now fairly well accepted in the astrophysics community. Yes, maybe, these set of assumptions are wrong and if they are, their nice constructed dark stars would not exist.... If the annihilation cross section was very very high, then all dark matter would have self-annihilated by now. So there are bounds on that. Yes, it is theoretically possible still, I suppose, that dark matter may not self-annihilate! That makes it harder to detect! Most favored particle physics phenomenology would suggest that there should be some annihilation cross-section, on the order of magnitude suggested by the measured strength of the weak-forces. It turns out that this annihilation cross section is low enough that most dark matter would have survived to this day after the ~14billion history of the universe.
A sufficiently advanced civilization that doesn't destroy itself first will inevitably optimize their environment to the point of harvesting every last drop of energy from their star(s), such that we can't detect anything but the gravitational effects.
This mysterious "dark matter" structure is termed a Matrioshka Brain (aka: Dyson Sphere).
I understand that this theory's still a bit too shocking for many to seriously consider, so "exotic particles" - or ANY other explaination - it must surely be.
Power to the Peaceful
Does it seem weird to anyone else? Now I haven't stayed up to date with dark matter, but they keep insisting that it MUST be there. It almost seems to be the ether that was claimed to be around us before Einstein blew that one open.
Note that dark matter is *not* regular matter. It is matter which does not interact through the electro-magnetic forces. It does not interact "with charged particles" nor with light! Hence, the name "dark." If light can not scatter from it, then that makes it "dark."
I can't help but see parallels between dark matter and the (al)chemist's Phlogiston theory. Phlogiston was used to account for quantitative errors in chemical reactions. Funny thing was, every (al)chemist had his own measurements for its properties, until our understanding of chemistry improved. I wouldn't be surprised if the dark matter theory were eventually tossed out the window because our understanding of gravity improved.
No, this is not an anti-matter star. Anti-matter is the "opposite" of particles that we are accustomed to, but still have the same interactions as the normal particles around us. So yes, they interact electro-magnetically. Say, you were a human being made of anti-matter on an anti-matter earth, in the part of the galaxy dominated by anti-matter, all visible physics laws would look the same. (Yes, there are one or two very weird experiments that would yield the opposite results. Feynman discusses this in his books, if you are interested.)
There are 4 forces, as we know it, in the universe. Gravitational, electro-magnetic, strong and weak. All these forces treat anti-matter pretty much the same way that they treat matter. Dark matter is something completely different. The reason is, it does not interact electro-magnetically. We know this cause we can "see" that it does not interact with photons( light )-- the force carrier of the electro-magnetic force. All observations agree that it does interact gravitationally. And whether or not it interacts weakly or not is under contention.
The significance of the results of dark matter experiments is very high. So, we pretty much, by now, know that dark matter exists and it does account for a large fraction of the energy budget of our universe, about ~22%. Good old normal matter accounts for about 4% of the energy budget.
Dark matter particles are probably flowing through you read this. They are around us. They interact only very very weakly and so we dont "feel" them. As their concentration is not very high, they do not contribute to our weight either. But they are around us, that's pretty clear.
If you think all this dark matter stuff sounds crazy, well, then a little factoid. About a billion neutrinos are passing through your eye-ball per second! They are mostly coming from the sun! And they flow through us, with extremely low probability of interacting, and with no real effect on our daily lives. Actually, the probability that ONE neutrino has interacted in the body of an 80-old person in his life time is about 50%. So that's a pretty rare event. The interaction of dark matter particles are on the same order of magnitude. For sometime, people thought that neutrinos could be dark matter candidates, until experiments showed that neutrinos are not heavy enough to account for ~22% of the energy budget of the universe.
So what does this whole thing mean? Dark matter particles are heavy particles, which do not like interacting with normal matter particles and mostly go about their own way, but still make their presence be felt, through gravity by structuring the universe through their overwhelming-numbers.
No it isn't. Spiral galaxies don't rotate like fixed plates. The spiral arms are density waves moving around galaxies and the rotation period of a star around the center of a galaxy varies with distance from the center of the galaxy. I don't know what astrophysicists need to do, but I do know that /. readers could do without people just making stuff up and trying to pass it off as science.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
The purpose of dark matter is not just to explain spiral galaxy rotational curves. The bigger problem is the energy budget of the universe.
If you ONLY read the NASA press releases with colorized images, that is, I am afraid your problem. There is over-whelming evidence for the existance of dark matter and what are scientists to do if the only thing that puts dark matter on a \.er's mind is just a pretty picture. If you are interested, go to arxiv.org and search for results from dark matter experiments and read the papers. Yes, they are technical. Yes, it produced many PhDs -- not a bad thing, last time I checked. And yes, the experimental evidence is overwhelming.
The number of people working on dark matter experiments, greatly exceeds the number of dark matter theorists, probably by an order of magnitude actually. This is *the* one field in astro-particle physics, where there is great wealth of data and that data is driving the evolution of the field. In particle physics, this is not the case! There is no data on particles which might form dark matter! There are too many theories! Hopefully, the tables will turn when the LHC at CERN turns on next year!
I should also point out that this is one of the "nicest" sort of theoretical astrophysics papers there is. It suggests a possible phenomena that produces an experimental signature in space experiments like or AMS.
"'dark stars'... 'they could still be with us'... 'ghosts'"
Geez, with Lucas announcing that more Star Wars movies are coming, it's sad that /. has been infiltrated by the Sith.
These are not the sequels you are looking for.
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See Clowe, Douglas et al (2006). "A Direct Empirical Proof of the Existence of Dark Matter," The Astrophysical Journal, ISSN 0004-637X, 648 (September 10): L109-L113.
It was big news at the time so Google will find you plenty of commentary online.
My own instincts suggest that we will eventually come to realise that dark matter and "dark energy" are as close as we will ever get to the main game in town and that baryonic matter will come to be seen as just the scum on the pond.
-- Our systemic servants do not good masters make.
>> Gravity doesn't obey Newton's laws on the very small scale (atomic)...
>
>What gives you that idea?
Quantum Gravity
"the first quantum-mechanical corrections to graviton-graviton scattering and Newton's law of gravitation have been explicitly computed (although they are so astronomically small that we may never be able to measure them)"
The moon--as in, Earth's moon--is just normal matter that doesn't glow. Oh, and Earth is too! Neither are dark matter.
That's not true. Earth does glow, quite strongly, in the infrared. The moon glows too, although at a slightly lower temperature (and thus longer wavelengths) due to lack of greenhouse effect.
However, Earth's infrared glowing is of course due to the sun's fusion output. Ie, Earth is in equilibrium, where it radiates as a blackbody the same amount of energy it that it absorbs from the sun.
So (as far as I know) a dark-matter planetoid at the same distance from the sun as Earth wouldn't have this infrared glow, because it wouldn't absorb solar photons. It would just exert a gravitational pull (or maybe have some other exotic effects). So you are correct, though, about dark matter being different from non-glowing (ie cold) 'regular' matter.
make world, not war
I'm confused, if we don't know what dark matter is, or if it even exists - why do we know that it would burn slowly?
Ace
Some sense at last. I just can't understand why rational people accept dark matter theories at face value, but claim to reject notions like 'ghosts' or 'god'.
Hell, here's my theory: Dark Matter = God. He's everywhere, invisible, and keeps the universe together! See, explains everything really.
The interesting thing about the whole dark matter episode, is that it probably gives an insight as to how religions form. Someone has a wild idea, that someone else expands on, that someone else tries to validate, that someone else uses as doctrine, that someone else teaches, that someone else uses to explain a wild idea...scary really. Eventually you end up with so many layers of analysis and reference that everyone's forgotten that the *original* idea was bunk. It's like an upside down house of cards.
lemonade was a popular drink and it still is
Although I'm not an astrophysicist, I have studied astrophysics as an undergraduate and know some things about dark matter theories and cosmology. You are absolutely correct in saying that dark matter must be non-baryonic under current models. Baryonic dark matter is excluded because big-bang nucleosynthesis models (which take observed primordial elemental abundances as input) show that only ~4% of the mass of the universe can be baryonic matter.
You are, however, incorrect in stating that dark matter shares no properties with ordinary matter besides gravity. All energy, including electromagnetic radiation and dark energy, affect the curvature of spacetime. Dark matter also has the property that it behaves in the same way as matter when the universe expands, i.e. that its density decreases as the cube of the scale factor (which determines the rate of expansion). Ordinary radiation and dark energy each behave differently in this regard, so dark matter is indeed uniquely matter-like in a very important way. Aside from galactic rotation curves, very good data from the WMAP project that studies the cosmic microwave background has determined that ~30% of the universe must be matter-like. Combined with the BBN studies, this means that 26% of the universe, by mass, is dark matter, which thus outnumbers ordinary matter by more than a factor of 6.
You are also incorrect in assuming that we haven't found dark matter. There is actually a very excellent photo of colliding galaxies that shows convincing evidence of dark matter. The caption does a decent job at giving an explanation of the photo's significance. If you want a more thorough explanation, both of the photo and why the result is significant, I recommend this blog maintained by several well-known cosmologists.
I would rather be killed by a terrorist than enslaved by my government.
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