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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.
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.
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:
This aspect of dark matter has always been troubling. If dark matter reacts gravitationally with ordinary matter, shouldn't we find the two combined within some sort of object? Everyone talks about how dark matter explains galactic rotation and cluster movement, but no one seems to say anything about what happens when you mix them. Why wouldn't dark matter collapse into a stellar interior along with the ordinary matter? How would this affect the nuclear processes within the star?
Why would there be "stars" made entirely of dark matter, anyway? What keeps ordinary matter from falling in?
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.
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."
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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
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.
Look at the bottom of this link. Dark matter and antimatter are two separate issues. Antimatter was verified with the observation of the positron that you mention in the 1930's and the existence of antimatter hasn't really been debated since then. Dark matter is something totally different... it's existence is suggested by astrophysical data and not by experimental particle physics. There is no theoretical understanding of dark matter. It's all suggested by observation. Of course, that's the way science is supposed to work, but in a few cases theoretical understanding preceded observation, as was the case with antimatter.