Dark Matter Stars in the Early Universe? 168
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."
Packing material (Score:3, Funny)
Nothing for you to see here. Please move along. (Score:5, Funny)
Indeed.
Hmm... what if we discover a star like the one Asimov described in Nemesis [wikipedia.org]? Yes, I know it wasn't a dark matter star, but they didn't see it, either.
That was illuminating! (Score:2)
Dark Star (Score:4, Funny)
Re: (Score:3)
Re: (Score:2)
i guess i could be - but if so, i'm really the last person qualified to answer the question.
Re: (Score:3, Funny)
Re:Dark Star (Score:4, Funny)
Re: (Score:2, Interesting)
No word yet from John Carpenter [wikipedia.org] on the prospect of solipsistic thermostellar bombs...
So, hey thanks for posting my submission, man, but enough with the sub-editing, already! Don't I got no artistic rights here? Now we see the violence inherent in the system! Don't give me any of that intelligent life crap... this is Slashdot. Just give me something I can troll. Help! Help! I'm being oppressed!!!
E_TOO_MUCH_PYTHON
Jerry Garcia Physics (Score:3, Funny)
interesting (Score:3, Interesting)
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
On the other hand, I wonder if we'll ever be able to make a gravity wave detector sensitive enough to detect dark matter. There's a lot of it, but it's pretty diffuse.
Re:interesting (Score:5, Interesting)
Why would there be "stars" made entirely of dark matter, anyway? What keeps ordinary matter from falling in?
Re: (Score:2, Informative)
There are theories about it being either this or special exotic particles or a mix of both. Your assuming it's all exotic particles.
Re: (Score:2, Interesting)
But that's just the thing. In some areas of space, say near a star or a galactic core, so much energy is blasting through space that no "normal matter" could not be luminescent. And yet, something in that area, that is *not* luminescent, is exerting a gravitational force.
Comment removed (Score:4, Insightful)
Re:Wrong, Wrong, Wrong (Score:4, Insightful)
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.
Re: (Score:3, Insightful)
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 tr
Re: (Score:2)
Because there is evidence, lots of it, for its existence.
Hell, here's my theory: Dark Matter = God. He's everywhere, invisible, and keeps the universe together! See, explains everything really.
But, see, real astrophysicists are a bit more discerning. We've been able, through single galaxy dynamics, cluster dynamics, and gravitational lensin
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Re:Wrong, Wrong, Wrong (Score:4, Interesting)
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 [nasa.gov] 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 [cosmicvariance.com] maintained by several well-known cosmologists.
Re: (Score:3, Interesting)
Re: (Score:2)
So? Unless you can come up with a feasible alternative explanation (and to my knowledge, there isn't one... I don't believe any of the popular MOND theories can explain the Bullet Cluster, though I may be wrong), the Bullet Cluster provides strong evidence for the existence of DM, whether or not you find the theory aesthetically pleasing or not.
Re: (Score:2)
Of course it is. You just have a restricted definition of "matter" which excludes, for instance, neutrinos. Neutrinos are massive fermions and deserve the label "matter" just as much as electrons do.
Under present models, dark matter exists only as a mathematical fudge.
It's not a mathematical fudge. There are a number of theories which naturally contain dark matter-like particles, completely apart from any motivation to explain the astrophysical observ
Re: (Score:2)
Re: (Score:2)
Several experiments are going on at the moment to detect dark matter the same way.
Re: (Score:2)
Dark matter is special in that it is capable of interacting with other matter generally only via either the weak nuclear force or gravity. These types of matter cannot interact via electromagnetism, meaning they really can't radiate any form of light, and given that the weak and gravitational interactions are so, ahem, weak, they are extremely difficult to detect, and their interactions with baryonic matter such as stars, planets, and you and me is extremely limited, and their interactions correspondingly
Re: (Score:2)
Not necessarily. Only if (a) there is enough of it around our part of the galaxy to detect, (b) it's possible to detect directly, and (c) it tends to stay around inside objects. Most dark matter would have to be in a spherical halo surrounding our galaxy, not in its disk. It doesn't interact strongly with other matter, so it would tend to pass right through instead of getting stuck in
Re: (Score:3, Informative)
That is incorrect
The theory is that immediately after the big bang, matter and antimatter began to annihilate. The asymmetry is explained partially through CP-Violation [wikipedia.org]. There are other theories such as axions (which could be a form of dark matter) that may explain the remainder of the asymmetry.
Re:interesting (Score:5, Informative)
The idea that the net sum product of the Big Bang is 0 (zero) mass and energy is old, and has been discarded for better theories.
Except that's not exactly right. Matter and antimatter annihilate, true, but they produce energy as the product of that annihilation. So it's not exactly a zero-sum-game as you seem to think. You may be getting confused by vacuum flux (a real phenomenon that has been experimentally observed), in which pairs of virtual particles and anti-particles are spontaneously created in a vacuum, only to disappear without a trace when they collide again. In that case, you end up with nothing (unless you're talking about a region of space arbitrarily close to the event horizon of a black hole -- that's how Hawking radiation works).
Try "never." The current standard model in cosmology posits that matter and antimatter were created in nearly equal quantities which condensed out of the energy of the Big Bang. The resultant mass reacted with itself, and the energy produced by these annihilations generated the next wave of particle creation. Eventually, a very slight bias in the production of matter vs. antimatter led to the overwhelming dominance of "normal" baryonic matter in the visible universe.
The idea that there are vast pockets of antimatter out there in the universe has been generally discarded. As for why there was a bias toward "normal" matter and against antimatter, I don't think that has ever been adequately explained, although there are several competing theories. It's interesting to note that in quantum mechanics, you can model antimatter interactions as a sort of time-reversal of matter interactions -- leading to the bizarre notion that antimatter is just normal matter that's "backwards" in time. Perhaps entropy provided enough of a "time arrow" to force a bias in the early universe's composition. (Or, as I sometimes muse, there might be some as-yet-unknown force that is responsible for breaking symmetry in time, and entropy as we understand it is just a product of this force.)
The "antimatter is just matter backwards in time" concept was kind of a shocker to me, taking quantum mechanics classes as a college undergrad. I'd been introduced to the concept by a story or novella that was published in Analog, and had dismissed the idea as hokey... and then one day, I cracked open one of my textbooks and saw a weird little diagram, and asked why there was an electron moving backwards in the time dimension, to which the professor responded, "That's a positron."
Re: (Score:3, Informative)
Spin one way, matter -- spin the other, antimatter (Score:2)
It's a bit like dancing, really. :)
My recollection's a bit fuzzy, but I seem to remember reading that all matter has "spin" to it. I put "spin" in quotes, as the sources I've read described it not so much as spin like what you get with a top, since elemental particles seem to approach true points, and therefore have no circumference that could spin around a center.
Anyway, I digress. The point I have is that everything has "spin". So does the anti-everything. If an electron has a spin of 1/2, then
Re: (Score:2)
Hm, memory is clearly failing me somewhere. :) Is it the magnetic moment then that's opposite, like what's found between neutrons and antineutrons (http://en.wikipedia.org/wiki/Antineutron [wikipedia.org])? I have a distinct recollection that the difference between electrons and positrons is more than just reversed charge, or otherwise chargeless particle and anti-particle pairs like for neutrons wouldn't work...
Re: (Score:2)
Re: (Score:2, Informative)
Missing: Anything Provable (Score:5, Insightful)
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 [cadbury.co.uk].
Other than being completely silly, am I making any fewer wild guesses than the Dark Matter Annihilation folks?
Re: (Score:1)
I actually kind of took the same viewpoint after reading TFA. Granted there may have been quite a bit of scientific research that went into it at some point. I just take issue when the article says things like
A team of researchers is proposing that....
or
that's what astronomers commonly believe.
because we don't know about the research, the level of credibility or even the number of people "astronomers" encompasses (quotes like that sometimes mean two astronomers they talked to when writing the article.)
With that aside I do get the feel that TFA is more assumption than science. If any
Actual research link (Score:5, Informative)
Here is the PDF: Dark matter and the first stars: a new phase of stellar evolution [arxiv.org]
Here is the abstract:
Read the article! (Score:2, Informative)
Ok, so say you are not a physicist, you can still read the article. It may have equations, but it is still English: [arxiv.org] http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.0521 v1.pdf [arxiv.org]
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.
Re:Missing: Anything Provable (Score:5, Funny)
Re: (Score:2)
Re: (Score:2)
Let 'er rip! (Score:2)
Forgive me, but your post read a bit differently for me --
...flatulence. At least, that's what the "fondant filling" in those durn Cadbury
Re:Missing: Anything Provable (Score:5, Informative)
An Arxiv paper doesn't really "count" as a publication for most purposes and certainly will not prevent you from "perishing" (that's what the peer-reviewed scientific journals are for).
Publishing in Arxiv is more like posting to a blog or slashdot where you semi-formally share your ideas and try to start up a discussion on the topic of interest to you.
Of course, some of the papers over there ended up being darn important.
Re: (Score:2)
Lessee:
dark matter - effects observed
phlogiston, aether - effects not observed
That wasn't no hard.
Burn so slow, they should be called WIMP stars (Score:1)
Dark Stars? (Score:3, Funny)
Re: (Score:3, Funny)
In strange Eons... (Score:1, Funny)
Predicted by Robert Hunter in 1969 (Score:2, Insightful)
Wouldn't they tend to collapse? (Score:5, Insightful)
Re: (Score:2)
Re:Wouldn't they tend to collapse? (Score:4, Interesting)
Re: (Score:2)
Imagine the simplest case -- a clump of matter over here and a clump over there. They're heading straight for each other and accelerating because they're attracted by gravity. If they don't interact in any other way, the
Re:Wouldn't they tend to collapse? (Score:5, Interesting)
Re: (Score:3, Interesting)
Ok, you're a hydrogen atom floating in DEEP space. You feel the tug of a galactic cluster, so you start moving towards it. Then you feel the tug of a galaxy, so you start moving towards it. Then you feel the tug of a random planet like the Earth, so you start moving towards it. All along you have been bumping into other
Re: (Score:2)
Only if there is enough mass within a certain radius. Even if it does not burn with nuclear fusion it would need ot have enough mass to bring it's radius down to a predefined number.
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Science and authors (Score:5, Insightful)
Re: (Score:2)
Brilliant except for the fact that, in lieu of any details about what dark matter is and with only a few details about what it isn't, what they are looking for is an almost entirely arbitrary expectation.
It's good to think outside the box and look for unusua
Re: (Score:2)
What I want to know... (Score:2)
What exactly is/was the dark matter annihilating with?
I thought antimatter and matter could annihilate...
Would the dark matter in fact be the regular matter that antimatter annihilates with in the proposed scenario?
Re: (Score:3, Informative)
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 t
Dark Matter == Alien Civilizations (Score:5, Interesting)
This mysterious "dark matter" structure is termed a Matrioshka Brain [aeiveos.com] (aka: Dyson Sphere).
I understand that this theory's still a bit too shocking [sysopmind.com] for many to seriously consider, so "exotic particles" - or ANY other explaination - it must surely be.
Re: (Score:2)
I'd like to believe that I think, though.
Re: (Score:2)
Re:Dark Matter == Alien Civilizations (Score:4, Insightful)
Further, recent observations of a pair of colliding galaxies [universetoday.com] conclusively shows that dark matter absolutely cannot be normal matter, since normal matter interacts with the EM force (which is producing drag on the colliding gas clouds), but dark matter does not (in the collision the dark matter clouds are just sliding past each other). Thus Dyson Sphere-covered stars, or star systems, dark matter is not.
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Dark Matter is the new Ether (Score:4, Interesting)
Re: (Score:2)
Re: (Score:2)
DM was observed unambigously last year (Score:4, Informative)
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.
Why I think Dark Matter isn't there. (Score:2)
I have an alternate explanation that explains the concept that the universe is expanding at an ever-increasing rate, Gamma-ray bursts, and the background noise in the Universe.
Namely: There wasn't ONE big bang and there isn't just ONE universe. I'm not talking about extra dimensions -- but that the universe that we experience is just one Clu
Re: (Score:2)
Re: (Score:2)
Since most of the energy of a supernova is supposed to be composed of neutrino emissions, and the Big Bang could definitely be considered a big explosion, they are saying that; a lot of the mass of the universe is basically the "missing mass" or Neutrinos (fast energy) and Neutron matter (cold, slow, not having electrical charge of electrons and protons).
That said, you could still have a Local, Big Bang, and have a much bigger Universe with more than one big b
Re: (Score:2)
I'm not sure I understand (Score:2)
Re: (Score:2, Informative)
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 w
Dark matter = modern phlogiston? (Score:3, Insightful)
Re: (Score:3, Informative)
Here's the quick overview:
On large scales the matter in the universe doesn't seem to behave as it should. We can explain this by hypothesizing extra matter we can't see. Others have attempted to explain it by hypothesizing that gravity doesn't work the way we think it should, AND that there's matter we can't see.
For various reasons it seems very likely that there are a set of very massive particles with certain properties. This is according
Besides Dark Matter (Score:2)
Every time I see this stuff I'm always curious if there is a dark matter explanation of why Voyager is slowing down more than Newtonian gravity would predict. If not, is some physicist going to come up with some more imaginary unsee-able stuff to expla
Re: (Score:2)
> why galaxy's don't fly apart?
No. General relativity isn't a set of heuristic equations that can be patched by adding some terms or jiggering some coefficients.
> Gravity doesn't obey Newton's laws on the very small scale (atomic)...
What gives you that idea?
Re:Besides Dark Matter (Score:4, Informative)
>
>What gives you that idea?
Quantum Gravity [wikipedia.org]
"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)"
Re: (Score:2)
Plus then you still have the problem of where all the supersymmetric particles went in the big bang. Dark matter solves that one nicely too. Solving two problems, one in cosmology and one in particle physics, with one hypothesis is pretty elegant.
Subliminal messages... (Score:3, Funny)
"'dark stars'... 'they could still be with us'... 'ghosts'"
Geez, with Lucas announcing [slashdot.org] 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.
Dark Stars (Score:3, Insightful)
Interesting stuff. (Score:2)
Discovering for certain things like that might change the way I look at the universe.
Heavy (Score:2)
So if one of these stars where big enough, we could have a Dark Black Hole?
Eep!
Re: (Score:1)
Re: (Score:3, Informative)
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.
Re: (Score:2, Interesting)
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 a