Dark Matter May be Easier to Detect than Previously Thought

Aug 10, 2009 By Lisa Zyga feature
Simulated all-sky maps of the Sommerfeld-enhanced annihilation surface brightness: In (A), there is no Sommerfeld enhancement, while in (B) and (C), the enhancement increases. Image credit: Kuhlen, Madau, and Silk.

(PhysOrg.com) -- The Milky Way, like many other galaxies, is thought to be embedded in massive, lumpy amounts of dark matter that release gamma rays and other emissions. Although at first these emissions seem too faint to detect, recent observations have shown that they may be stronger than previously thought. In a new study, scientists have developed a model that predicts that gamma rays from hundreds of dark matter clumps should be detectable by the Fermi satellite that was launched in June 2008.

In their study published in a recent issue of , Michael Kuhlen of the Institute for Advanced Study in Princeton, Piero Madau of the University of California, Santa Cruz, and Joseph Silk of the University of Oxford have investigated how the from cold annihilations can be enhanced by orders of magnitude by the Sommerfeld effect. While previous calculations have shown that only a handful of the most massive dark matter halos should emit detectable by satellites, accounting for the Sommerfeld effect suggests otherwise.

“Annihilation is a quantum mechanical process that can occur whenever a particle and its antiparticle collide,” Kuhlen told PhysOrg.com. “It turns out that in many promising particle physics models the dark matter particle is its own antiparticle. In that case you only need to get to sufficiently high densities for dark matter particles to have a reasonable chance to collide with each other and hence to annihilate. It turns out that the predicted dark matter densities at the centers of subhalos are high enough that a large enough number of annihilation events might occur for Fermi to have a chance to detect the resulting radiation. Especially if the Sommerfeld effect is important.”

As the researchers explain, the Sommerfeld effect is the result of a long-range between that effectively increases the dark matter annihilation rate. When analyzing the experimental results of other satellites, researchers discovered a surprisingly large amount of electron and antimatter emissions. The Sommerfeld effect, they suggest, might explain these puzzling signals.

To explore this possibility, the researchers applied the Sommerfeld correction to simulations that use more than one billion particles to model the formation of a dark matter halo the size of the Milky Way. They found that, after they applied the corrections, smaller subhalos (and even smaller “subclumps”) are much more clearly visible than in previous predictions. When compared to expected backgrounds, the researchers predict that, even in conservative cases, ten or more subhalos should be discovered after five years of searching by the Fermi satellite. They also predict that Fermi should be able to detect some of these subhalos in its first year of observation, a prediction that will soon be tested.

If the researchers are correct, dark matter detections could open up the door to interesting possibilities such as non-gravitational dark matter interactions and new particle physics.

“That would be a spectacular confirmation of the particle nature of dark matter [if the Fermi satellite does detect dark matter annihilation],” Kuhlen said. “It would certainly result in a Nobel Prize for someone on the Fermi team. Don't forget that we have no direct evidence of dark matter. Over the last 70-80 years astronomers have amassed numerous independent observational pieces of evidence for its existence, and theory provides many plausible particle candidates. As a result, dark matter is a firm part of the standard paradigm of cosmological structure formation. Nonetheless, it would be great to get some more direct confirmation of this hypothesis. Detecting the products of dark matter annihilation would provide such evidence. Furthermore it would shed light on the nature of the dark matter particle: its mass and its annihilation cross section, for example.”

More information: Michael Kuhlen, Piero Madau, Joseph Silk. “Exploring Dark Matter with Substructure.” Science Express. 10.1126/science.1174881.

Copyright 2009 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

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User comments : 44

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El_Nose
4.9 / 5 (14) Aug 10, 2009
^
|

i am sorry WTF are you talking about?
jaggspb
4.9 / 5 (9) Aug 10, 2009
Does any one speak crazy?
zealous
4.9 / 5 (9) Aug 10, 2009
I think he's talking about a biological capacitor for the excess energy from the big bang. I dunno though most of it's gibberish to me. He might be one of those fellows that hopes big words and long winded descriptions will distract you from what he's saying.
MorituriMax
4.8 / 5 (6) Aug 10, 2009
Does any one speak crazy?


No, but I speak jibber jabber and I really pity him.
otto1923
4.6 / 5 (5) Aug 10, 2009
I think maybe its poetry of some sort.
Parsec
4.5 / 5 (4) Aug 10, 2009
It is quite puzzling to me how we could separate out the signal from ordinary matter/anti-matter annihilation and dark matter ones. I mean, what is being reported are actually signals from electron/positron events. Anything that explains a higher than expected density of positrons in the halo would also account for the increased signal. If for example, as has been reported, positrons were emitted from supernova at a higher than expected velocity they would have a longer mean path before encountering an electron.

At any rate, whether this is or is not true is not the point. The question is... how could the possibility be eliminated?
degojoey
4.4 / 5 (7) Aug 10, 2009
some people really need help.. me being one of them because i read that stupid ass horrible comment all the way through. i would pay money to get back that time and the time i felt it was necessary to complain about the douchebag that wrote that comment. die loser.
yyz
5 / 5 (2) Aug 10, 2009
The crucial point here may be the redshift (or blueshift) of the emitter of the 511keV annihilation radiation (See wiki page for info on electron-positron annihilation here: http: http://en.wikiped...adiation ) This determination may provide an important clue as to the nature of dark matter or of the source of the annihilation emission line.
Ant
3.5 / 5 (4) Aug 10, 2009
yet another computer simulation
Noumenon
4.8 / 5 (48) Aug 10, 2009
Odd that a (dark matter) particle could be it's own anti-particle,...hmm, kind of like if I were my own evil twin.
brant
1 / 5 (1) Aug 10, 2009
How come their equations dont tell them what dark matter is??
E_L_Earnhardt
2.3 / 5 (3) Aug 10, 2009
I think it's ANGELS! 'Like to join the band?
NeilFarbstein
4 / 5 (4) Aug 11, 2009
Does any one speak crazy?
A lot of people. Does anyone speak sane?
ea1th
not rated yet Aug 11, 2009
Does any one speak crazy?


Talking of speaking crazy....How for pity's sake can a particle be its own anti-particle? Can/cannot anyone enlighten/confuse us a little on the subject?


Adriab
4.8 / 5 (5) Aug 11, 2009
It is quite puzzling to me how we could separate out the signal from ordinary matter/anti-matter annihilation and dark matter ones. I mean, what is being reported are actually signals from electron/positron events. Anything that explains a higher than expected density of positrons in the halo would also account for the increased signal. If for example, as has been reported, positrons were emitted from supernova at a higher than expected velocity they would have a longer mean path before encountering an electron.



At any rate, whether this is or is not true is not the point. The question is... how could the possibility be eliminated?


Just a note: dark matter does not have to be some mysterious exotic substance. It could be as simple as "stuff our instruments have a hard time detecting" which could easily be our every-day matter/antimatter.

Although, most times when I read or hear the phrase "Dark matter", the writer/orator is meaning the exotic flavor.
Adriab
not rated yet Aug 11, 2009
Odd that a (dark matter) particle could be it's own anti-particle,...hmm, kind of like if I were my own evil twin.


Photons are their own anti-particle. As long as they have opposite spin, that is.

It was proposed somewhere (sorry I have no reference for you) that exotic dark matter could be composed of photons behaving in a strange and never-before-detected way. Not sure about that proposition (there is an issue with mass), but it would be interesting to investigate.
Velanarris
4.4 / 5 (8) Aug 11, 2009
Dark matter and dark energy are terms that say "We don't know what it is." Nothing more, nothing less. Something is happening, and we can't explain why so we've developed the "dark mechanisms" to fill the gap.

Dark matter and dark energy very well could just be the effects of normal gravity in an unknown situation.

Secondly, if Dark matter produces gamma radiation on annihilation, and it's omnipresent (or close to it) in the Solar system, one would think that any Gamma detection device, of sufficient sensitivity, would detect something akin to the microwave background radiation detected by the first radio telescopes.

I can't speak to the referenced paper as I haven't read it yet, but to build such a large and tenuously understood theory upon an unknown framework such as dark matter is akin to stating there's a pink elephant in the room that no one can see.

I remain unimpressed with dark matter theory.
LuckyBrandon
5 / 5 (2) Aug 11, 2009
wont it be a bitch if we discover the stuff is in fact real, then discover like all matter, we cant pass through it, so we're stuck in our solar system anyways :|
....just erroneous thinking...
Ant
1 / 5 (3) Aug 11, 2009
adriab
I agree with that, if they dont know what it is they have to make it ezotic. why dont they just say " we are too stupid to understand"
zealous
5 / 5 (4) Aug 11, 2009
Ant, you can't exactly call a large chuck of the unknown "too stupid to understand". That's why we have fancy names for things. Name them first then find out what they are. Kinda like black holes, worm holes, dark matter/energy. Its just their way of having a placeholder name for a concept before they find out what it really is.
frajo
2.8 / 5 (4) Aug 11, 2009
It's ok to name the unknown with a placeholder. But that placeholder should not be misleading.
By naming something unknown "dark matter" the not-so-well informed public is mislead to rule out all thinkable explanations based on "non-matter" like strings, branes, advanced gravity concepts etc.
MorganW
5 / 5 (3) Aug 11, 2009
If someone were to propose a hypothesis that virtual particles are constantly "popping" into and out of existence couldn't he/she start trying to prove it by looking for their possible effect on gravity based on their accumulated (albeit temporary) increase in mass? It may not be something that you could directly observe without knowing exactly when/where to look, but if you have enough activity throughout the galaxy, it could tip the scales.
I'm just trying to turn the argument around to see if it makes more sense that way. Something I've been thinking about for a while and thought I'd throw it out there. Maybe it's already been proposed and tossed out as junk.
Azpod
5 / 5 (3) Aug 11, 2009
yet another computer simulation

Yes, but one that demonstrates a testable hypothesis as to how dark matter might be detected. If the hypothesis proves to be false, then we know more about the Sommerfeld effect and possibly the nature of dark matter itself. Not much of a consolation prize, mind you, but it's still more than we know today.

If the hypothesis is correct... we'll finally have a way to detect dark matter. And in doing, we'll finally be able to unlock a whole lot of information about its nature and by extension the nature of the Universe itself.
Velanarris
4.8 / 5 (4) Aug 11, 2009
If someone were to propose a hypothesis that virtual particles are constantly "popping" into and out of existence couldn't he/she start trying to prove it by looking for their possible effect on gravity based on their accumulated (albeit temporary) increase in mass? It may not be something that you could directly observe without knowing exactly when/where to look, but if you have enough activity throughout the galaxy, it could tip the scales.

I'm just trying to turn the argument around to see if it makes more sense that way. Something I've been thinking about for a while and thought I'd throw it out there. Maybe it's already been proposed and tossed out as junk.

Vacuum energy postulate. It's a good concept and rather well understood in a mathematical sense. Vacuum annihilation is one of the leading candidates explaining the accelerating expansion. As the "vacuum" grows, the surface area affected by vacuum annihilation interactions causes an energetic reaction with space-time.

The only issue is you have ot understand and accept quite a few relative unknowns in the realm of the really really small to believe in it affecting the really really big.
MorganW
5 / 5 (2) Aug 12, 2009
Thanks Velanarris! So let's postulate a little further and imagine that gravity acts simultaneously and equally upon all things with mass including light. I don't know whether it requires something with mass in order to manifest gravity or if gravity causes things to acquire mass, but if it acts on everything equally, there would have to be a LOT of these "virtual particles" in order for us to be able to measure their effect. I don't know if this is correct but I have an easier time wrapping my mind around this than cosmic strings or other more esoteric theories.
Velanarris
4.7 / 5 (3) Aug 12, 2009
Actually vacuum annihilation, as I understand it, is a quantum fluxuation.

Basically a particle and antiparticle come into existence and annihilate each other resulting in a relase of energy. The difficult portion is where to the particles come from? Right now the best answer is they're borrowed from the future or past through manipulation of quantum probability for particle existence within that space at that time.

It doesn't get extraordinarily hairy until you include the potential for "Hawking Radiation" which is when these particle-antiparticle pairs come into existence near or within the event horizon of a black hole where the anti-particle is pulled into the black hole annihilating a particle that was part of the black hole, (hence the term "evaporation"). This is tricky because it leaves a particle in place that either joins the mass of the black hole, is ejected from the black hole at near light or light speed, or the particle simply ceases to exist. The latter of these 3 violating the conservation of energy postulate as you've witnessed the creation of an antiparticle from nothing.
DozerIAm
3 / 5 (4) Aug 12, 2009
Dark Matter is a hypothetical concept to paper over the butts of physicists who's gravitation formulae come shy for what the mass of the universe should be. So rather than chasing possibly non-existent matter, why aren't we making better formulae to predict the behavior of gravitation?
Ant
1 / 5 (1) Aug 12, 2009
hi zealous! sorry I didnt get back earlier but Tuesday and Friday nights are the only chances I get to sleep. Naming anything with a descriptive title implies understanding of that entity. Which in turn intimidates the lesser knowledgeable into to believing they are uneducated in the topic and therefore cannot contribute to the discussion.
Ant
1 / 5 (2) Aug 12, 2009
Hi Velanarris!
You mention universal expansion. Are you sure it is expansion and not growth? The effect would appear the same but the effects dramatically different. in the last 20 years of reading I have seen two articles which suggest that the so called expansion is not constant but happens in steps which suggests that modification is growth rather than streching of the universe. Sorry I have no reference to either of these articles the second was some years ago but after I joined physorg.
Ant
1 / 5 (1) Aug 12, 2009
As I have said before if dark matter comprises 95 percent of the universe it has to be a structure which is all pervading and should be locatable. As it is not yet understood I would suggest again "We are too thick to understand"
MorganW
5 / 5 (3) Aug 12, 2009
OK, you mention universal expansion and now I'm just going to throw all caution to the wind.
If distance is measured in units of time (light years) at cosmic scales, how do we know if it's a physical expansion vs. time simply "speeding up"? Many people imagine some sort of "edge" to the Universe, after all there was a big bang, they think, so what's outside that? My thought is that we're at the edge (so to speak) at this very second. The concept of "now" is already gone the moment you think of it/thought of it. But "now" as a dimension of time, is occurring everywhere, all at once in all directions and we're riding on it like a wave. If it were to speed up we wouldn't notice it, but we might see some affect of it.
Velanarris
3 / 5 (2) Aug 12, 2009
Dark Matter is a hypothetical concept to paper over the butts of physicists who's gravitation formulae come shy for what the mass of the universe should be. So rather than chasing possibly non-existent matter, why aren't we making better formulae to predict the behavior of gravitation?

Exactly my point.
vidyunmaya
1 / 5 (7) Aug 14, 2009
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Corvidae
not rated yet Aug 14, 2009
The latter of these 3 violating the conservation of energy postulate as you've witnessed the creation of an antiparticle from nothing.



Which makes me wonder if a fast/powerful enough magnetic wave front would be able to cause the effect intentionally. Doubtful you could get energy out of it, but you might be able to prove/disprove the hypothesis.
fuzz54
3.7 / 5 (3) Aug 14, 2009
How come their equations dont tell them what dark matter is??

Equations can't tell us what something is. We don't know what an electron is, but we can observe it. The same goes for dark matter.
frajo
3.3 / 5 (3) Aug 14, 2009
How come their equations dont tell them what dark matter is??


Equations can't tell us what something is.


Yes; it's the other way round: you've gotta know or at least assume what something is before you can insert it into an equation.

We don't know what an electron is, but we can observe it. The same goes for dark matter.


No - the electron holds a very solid position in the particle physicists' standard model; DM holds no position at all in that model.

BrianH
3.5 / 5 (2) Aug 15, 2009
It is quite puzzling to me how we could separate out the signal from ordinary matter/anti-matter annihilation and dark matter ones. I mean, what is being reported are actually signals from electron/positron events. Anything that explains a higher than expected density of positrons in the halo would also account for the increased signal. If for example, as has been reported, positrons were emitted from supernova at a higher than expected velocity they would have a longer mean path before encountering an electron.



At any rate, whether this is or is not true is not the point. The question is... how could the possibility be eliminated?

The self-annihilation events of DM particles meeting in the dark are not "the same" as electron/positron encounters. The bandwidth of gamma emission possibilities and signals is immense; I'm sure they will be distinct.
Velanarris
5 / 5 (3) Aug 16, 2009
The self-annihilation events of DM particles meeting in the dark are not "the same" as electron/positron encounters. The bandwidth of gamma emission possibilities and signals is immense; I'm sure they will be distinct.
But if you don't know what Dark Matter is then you can't say that with certainty, can you?
Scryer
1 / 5 (1) Aug 17, 2009
Yes, Spatial Gravity Anomolies in space, it's hard to tell what is causing that. What is it?
Au-Pu
1 / 5 (1) Aug 22, 2009
Ant: Aug 10 is correct. This is just another computer simulation.
Computer simulations can produce whatever outcomes their designers want.
What intrigues me is why so much effort is being put into searching for so-called dark matter and dark energy when it is all simply an effort to patch up an unworkable Big Bang theory.
If any other theory were put forward where 80% of the matter needed to support it was missing it would be disregarded by all.
Why not devote all this time, effort and money on new more provable better supported ideas.
Or the big bang enthusiasts could advance to the past and adopt the "ether" as their solution.
If they care to recall the "ether" was supposed to fill all of space and all spaces between everything and to be the means by which all things were propagated.
Surely it would be easier to revive this as their answer.
I mean there are still people who believe that the Earth is flat so why not accept the "ether" as the solution to all the big bang problems.
Alexa
3 / 5 (2) Aug 23, 2009
..the "ether" was supposed to fill all of space and all spaces between everything ..
In AWT Aether isn't pervading the space, but it forms a space instead in similar way, like water is forming surface for wave spreading. It's true luminiferous Aether, not just some obstacle in space, which the light wave is supposed to overcome during its travel through ordinary space. That's a subtle, but significant difference in concepts.

Aether concept is indeed adhoced in the same way, like Flat Earth hypothesis - but Flat Earth cannot explain so much problems and questions of contemporary physics, like the dense Aether concept. In fact, dense Aether introduces logical solution of "small problem" (how Universe got into small singularity and why it exploded) by substantially large problem (where we got infinitely hot and dense Aether from?) at the price.
Velanarris
4.5 / 5 (2) Aug 24, 2009
..the "ether" was supposed to fill all of space and all spaces between everything ..
In AWT Aether isn't pervading the space, but it forms a space instead in similar way, like water is forming surface for wave spreading. It's true luminiferous Aether, not just some obstacle in space, which the light wave is supposed to overcome during its travel through ordinary space. That's a subtle, but significant difference in concepts.



Aether concept is indeed adhoced in the same way, like Flat Earth hypothesis - but Flat Earth cannot explain so much problems and questions of contemporary physics, like the dense Aether concept. In fact, dense Aether introduces logical solution of "small problem" (how Universe got into small singularity and why it exploded) by substantially large problem (where we got infinitely hot and dense Aether from?) at the price.

I think we're all just about fed up with AWH.
Math or GTFO.
Slotin
3 / 5 (2) Aug 25, 2009
Well, exactly. In formal math you should prove every theorem by robust predicate logics first, before it can be used in further derivations. So we should understand subject at the level of predicate logics first, after then we can derive some formal model.
Velanarris
5 / 5 (2) Aug 25, 2009
Well, exactly. In formal math you should prove every theorem by robust predicate logics first, before it can be used in further derivations. So we should understand subject at the level of predicate logics first, after then we can derive some formal model.

Not seeing any math there Alexa/Slotin/Alizee.

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