Astronomers report that dark matter 'halos' may contain stars, disprove other theories

Oct 24, 2012

Could it be that dark matter "halos"—the huge, invisible cocoons of mass that envelop entire galaxies and account for most of the matter in the universe—aren't completely dark after all but contain a small number of stars? Astronomers from UCLA, UC Irvine and elsewhere make a case for that in the Oct. 25 issue of the journal Nature.

Astronomers have long disagreed about why they see more light in the universe than it seems they should—that is, why the infrared light they observe exceeds the amount of light emitted from known .

When looking at the cosmos, astronomers have seen what are neither stars nor galaxies nor a uniform dark sky but mysterious, sandpaper-like smatterings of light, which UCLA's Edward L. (Ned) Wright refers to as "fluctuations." The debate has centered around what exaclty the source of those fluctuations is.

One explanation is that the fluctuations in the background are from very distant unknown galaxies. A second is that they're from unknown galaxies that are not so far away, faint galaxies whose light has been traveling to us for only 4 billion or 5 billion years (a rather short time in astronomy terms). In the Nature paper, Wright and his colleagues present evidence that both these explanations are wrong, and they propose an alternative.

The first explanation—that the fluctuations are from very distant galaxies—is nowhere close to being supported by the data the astronomers present from NASA's , said Wright, a UCLA professor of physics and astronomy.

"The idea of not-so-far-away faint galaxies is better, but still not right," he added. "It's off by a factor of about 10; the 'distant galaxies' hypothesis is off by a factor of about 1,000."

Wright and his colleagues, including lead author Asantha Cooray, a UC Irvine professor of physics and astronomy, contend that the small number of stars that were kicked to the edges of space during violent collisions and mergers of galaxies may be the cause of the infrared light "halos" across the sky and may explain the mystery of the excess emitted .

As crashing galaxies became gravitationally tangled with one another, "orphaned" stars were tossed into space. It is these stars, the researchers say, that produce the diffuse, blotchy scatterings of light emitted from the galaxy halos that extend well beyond the outer reaches of galaxies.

"Galaxies exist in that are much bigger than the galaxies; when galaxies form and merge together, the dark matter halo gets larger and the stars and gas sink to the middle of the the halo," said Wright, who holds UCLA's David Saxon Presidential Chair in Physics. "What we're saying is one star in a thousand does not do that and instead gets distributed like dark matter. You can't see the dark matter very well, but we are proposing that it actually has a few stars in it—only one-tenth of 1 percent of the number of stars in the bright part of the galaxy. One star in a thousand gets stripped out of the visible galaxy and gets distributed like the dark matter.

"The halo is not totally dark," Wright said. "A tiny fraction, one-tenth of a percent, of the stars in the central galaxy has been spread out into the halo, and this can produce the fluctuations that we see."

In large clusters of galaxies, astronomers have found much higher percentages of intra-halo light, as large as 20 percent, Wright said.

For this study, Cooray, Wright and colleagues used the Spitzer Space Telescope to produce an infrared map of a region of the sky in the constellation Boötes. The light has been travelling to us for 10 billion years.

"Presumably this light in halos occurs everywhere in the sky and just has not been measured anywhere else," said Wright, who is also principal investigator of NASA's Wide-field Infrared Survey Explorer (WISE) mission.

"If we can really understand the origin of the infrared background, we can understand when all of the light in the universe was produced and how much was produced," Wright said. "The history of all the production of light in the universe is encoded in this background. We're saying the fluctuations can be produced by the fuzzy edges of galaxies that existed at the same time that most of the stars were created, about 10 billion years ago."

The research was funded by the National Science Foundation, NASA and 's Jet Propulsion Laboratory.

Future research, especially with the James Webb Space Telescope, should provide further insights, Wright said.

"What we really need to be able to do is to see and identify the galaxies that are producing all the light in the infrared background," he said. "That could be done to a much greater extent once the James Webb Space Telescope is operational because it will be able to see much more distant, fainter galaxies."

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Tuxford
1.6 / 5 (13) Oct 24, 2012
Perhaps Ned is 'blantantly' ignoring this news, indicating that surprisingly, stars move away from our galactic center with radial velocity increasing with distance.....Oh how inconvenient...2plus2...

http://phys.org/n...ays.html

Lurker2358
2.3 / 5 (6) Oct 24, 2012
Perhaps Ned is 'blantantly' ignoring this news, indicating that surprisingly, stars move away from our galactic center with radial velocity increasing with distance.....Oh how inconvenient...2plus2...


Incredible.

I don't seem to have been reading around that particular time when that article was posted.

That actually suggests that most stars should be ejected from the Galaxy within about 1.2 billion years, but the Galaxy is supposedly 10 or 11 billion years old, so why does it exist in the form it's in?

Is the white hole hypothesis true after all?!

How did I miss that article?
antialias_physorg
4.1 / 5 (18) Oct 24, 2012
I don't seem to have been reading around that particular time when that article was posted. That actually suggests that most stars should be ejected from the Galaxy within about 1.2 billion years,

Erm. How about: no?

Maybe you missed these parts:
"A tiny fraction, one-tenth of a percent, of the stars in the central galaxy has been spread out into the halo"
and
"One star in a thousand gets stripped out of the visible galaxy and gets distributed like the dark matter."
and
"that were kicked to the edges of space during violent collisions and mergers of galaxies"

... and basically all the rest of the article.

I know it's hard when that empty comment field is beckoning. But reading the article before commenting might actually be a good idea. It's novel and unorthodox, I grant you - but nevertheless: please consider it.
eachus
4.4 / 5 (7) Oct 24, 2012
Perhaps Ned is 'blantantly' ignoring this news, indicating that surprisingly, stars move away from our galactic center with radial velocity increasing with distance.


Or perhaps what he is studying is completely unrelated. The RAVE data may indicate that our spiral arm is moving away from the center of the galaxy. More likely the center of gravity is not where we think it is. A ten percent error in R squared requires less than a five percent error in R. Do we know the distance to Sag A* that accurately? Not really. Do we know that Sag A* is at the center of gravity for the Milky Way? Again, not really. We have seen many other galaxies with supermassive black holes displaced from the center. (The actual number would be more than we can count, since the displacement could be toward or away from us.)

As for the study here, we do know of a few outlying stars around the Milky Way. Finding similar stars around the Andromeda galaxy will be much easier with new telescopes.
Tuxford
1.4 / 5 (9) Oct 24, 2012
Well perhaps we should forgive Ned for his oversight. I know he is certainly Embarrassed about this one, after he claimed the opposite for so many years, relying on selective data cherry picking. I am afraid Ned can't really think. Let us pray...

http://phys.org/n...752.html

Lurker2358
2.1 / 5 (7) Oct 24, 2012
AP:

In the article linked to by Tuxford it states that 10km/s is the average velocity OUTWARD of 200,000 stars in a survey of stars within 6000 ly from the Sun.

I did NOT misunderstand the article, it says so twice, in two different ways.

http://phys.org/n...ays.html

I read both articles completely, BTW.

Moreover, rogue stars or otherwise inter-galactic stars don't surprise me by any means, with or without galactic collisions.

Some of these stars might not even be "rogues". They may have simply formed in the "middle of nowhere" from whatever materials happened to be there.

It's another example of people carrying text book examples to absurdities if they thought stars only existed in Galaxies.

Why are so many people in the mainstream physics community sometimes indistinguishable from rigid-thinking idiots? No offense to anyone personally, but this is pretty obvious stuff they should have been looking for from the beginning.
Lurker2358
1.8 / 5 (5) Oct 24, 2012
Eachus:

Spiral arms should actually produce a mechanism of tidal forces, which should transfer angular momentum from the inner matter to the outer matter over time.
ValeriaT
3.6 / 5 (5) Oct 24, 2012
This finding is not so surprising. Many stars could be ejected with gravitational slingshot at the large distance. In addition, many large galaxies are surrounded with satellite galaxies, which may release their stars as well..
StarGazer2011
1 / 5 (3) Oct 24, 2012
so wouldnt this be more easily observable in nearby galaxies rather than only looking at the distant ones?
Also the pattern should still be localised around visible galaxies only, it doesnt explain patches of IR comming from anywhere not associated with a nearby galaxy right?
Urgelt
3.3 / 5 (3) Oct 25, 2012
This article, and the research it describes, sure leaves a lot of unanswered questions. For example, if the presumed halo stars are so rare and so difficult to observe, how is it that we can ascribe to them a rather large excess in infrared light production? It doesn't add up. If they were collectively adding enough infrared to make up the difference, taken in context with with their proposed rarity, they ought to be observable at distances less than 5 billion light-years.

Perhaps halo stars are responsible for some small portion of the the excess infrared radiation we're seeing, but I suspect it isn't a sole and complete answer.
VendicarD
5 / 5 (1) Oct 25, 2012
I have never seen a simulated galactic merger that wasn't exceptionally dirty.

The stars flung away from the results of the coalescence of two galaxies have to go somewhere.

http://www.youtub...GiqPdbx8
Moebius
3 / 5 (2) Oct 25, 2012
If dark matter gathers by attraction to itself like regular matter, wouldn't it clump together like regular matter to form solid bodies?
Graeme
5 / 5 (2) Oct 25, 2012
The lower mass stars would be given higher velocities in these kinds of encounters, so such a halo would preferentially be full of planets, asteroids, and red dwarfs.
radek
1 / 5 (1) Oct 26, 2012
If dark matter gathers by attraction to itself like regular matter, wouldn't it clump together like regular matter to form solid bodies?


good point. Is there any research about this question?
ValeriaT
1 / 5 (9) Oct 26, 2012
In AWT the gravity is the result of gravitational wave shielding between massive bodies. And the cold dark matter is the result of the shielding of this shielding with another massive bodies. Therefore the distribution of cold dark matter around massive body cannot change until the distribution of another massive bodies around it doesn't change. This is very rough description, though. The clouds of cold dark matter cannot interact mutually (they rather tend to repulse mutually at large distances, which is sometimes interpreted as so-called dark energy), but they can both create, both attract the massive particles thus forming hot dark matter into itself, which indeed does attract the massive bodies and it can lead to Gregory-Laflamme instability, for example. So I presume, when dark matter cloud grows above certain limit, it may collapse gravitationally and form the quasars.
Fleetfoot
4.4 / 5 (7) Oct 28, 2012
If dark matter gathers by attraction to itself like regular matter, wouldn't it clump together like regular matter to form solid bodies?


No, solid matter is held together by EM forces and "dark matter" is so called because it does not interact with EM. As it clumps gravitationally, it will simple produce a ball or ellipsoid governed by the Virial Theorem. Dark matter particles don't even collide, they pass straight through each other as shown by the Bullet Cluster.
Fleetfoot
4.5 / 5 (8) Oct 28, 2012
In AWT ..


There is no such thing as "AWT".

gravity is the result of gravitational wave shielding between massive bodies.


That is the idea first published by Fatio de Duillier around 1690 and plagiarised by Lesage in 1758. It fails because the impact of the "ultramundane" particles would heat any body at an enormous rate. The Earth would be vapourised in a fraction of a second for example.

http://www.mathpa...h041.htm

We have been over this topic many times, why are you still repeating something you know to be wrong?
radek
1 / 5 (3) Oct 28, 2012
If dark matter gathers by attraction to itself like regular matter, wouldn't it clump together like regular matter to form solid bodies?


No, solid matter is held together by EM forces and "dark matter" is so called because it does not interact with EM. As it clumps gravitationally, it will simple produce a ball or ellipsoid governed by the Virial Theorem. Dark matter particles don't even collide, they pass straight through each other as shown by the Bullet Cluster.


solid matter is held togeather by gravity. How dark matter interacts with regular matter?
Fleetfoot
4 / 5 (4) Oct 28, 2012
If dark matter gathers by attraction to itself like regular matter, wouldn't it clump together like regular matter to form solid bodies?


No, solid matter is held together by EM forces and "dark matter" is so called because it does not interact with EM. As it clumps gravitationally, it will simple produce a ball or ellipsoid governed by the Virial Theorem. Dark matter particles don't even collide, they pass straight through each other as shown by the Bullet Cluster.


solid matter is held togeather by gravity.


Pick up a rock. What is holding it together? Gravity pulls it toward the Earth but doesn't give it its solid structure.
radek
1.5 / 5 (2) Oct 28, 2012
If dark matter gathers by attraction to itself like regular matter, wouldn't it clump together like regular matter to form solid bodies?


No, solid matter is held together by EM forces and "dark matter" is so called because it does not interact with EM. As it clumps gravitationally, it will simple produce a ball or ellipsoid governed by the Virial Theorem. Dark matter particles don't even collide, they pass straight through each other as shown by the Bullet Cluster.


solid matter is held togeather by gravity.


Pick up a rock. What is holding it together? Gravity pulls it toward the Earth but doesn't give it its solid structure.


true I should have been precise and asked how solid bodies like planets were created. It was gravity. Clumps of dust attracted more and more dust.

What about dark matter question?
Q-Star
3 / 5 (6) Oct 28, 2012
What about dark matter question?


The answer he offered is still the same. Those "dust" particles come into the general area through the over-all pull of the combined gravity all the particles, but they only stick together due to the electromagnetic force, as all molecular bonds do. Were it not for the electromagnetic forces binding them together they would endlessly break back apart due to repeated collisions. It's the big lumps that have enough mutual gravity to affect anything at a distance, which dark matter certainly does. But remember, dark matter does not interact with regular matter through the electromagnetic force, that is why it is dark, it can not radiate energy.

Keep in mind that the electromagnetic force is many orders of magnitude greater than gravitational force.

The reason that dark matter is dark, is because it does not interact with regular matter through the really strong forces.
Fleetfoot
3.7 / 5 (3) Oct 29, 2012
Pick up a rock. What is holding it together? Gravity pulls it toward the Earth but doesn't give it its solid structure.


true I should have been precise and asked how solid bodies like planets were created. It was gravity. Clumps of dust attracted more and more dust.

What about dark matter question?


"Q-Star" has really answered this but in case it isn't clear, think of the animations you've probably seen of the Earth forming with a flow of asteroids hitting it. Each one melts a patch of the surface and merges with the lava because it gets stopped on contact with the surface due to EM forces.

That can't happen with dark matter, if a new particle was pulled by gravity towards a ball of particles, it would pass right through them. It's path might be deflected a little by gravitational interactions but that's all. What you would get is a cluster of particles like the stars in a globular cluster. That is a "dark matter halo".
radek
1 / 5 (3) Oct 29, 2012

That can't happen with dark matter, if a new particle was pulled by gravity towards a ball of particles, it would pass right through them. It's path might be deflected a little by gravitational interactions but that's all. What you would get is a cluster of particles like the stars in a globular cluster. That is a "dark matter halo".


In fact this is only hypothesis. We can observe efects caused by "dark metter" and it`s the only thing wchich is confirmed. We still don`t know what the dark matter is and if it consists of unknown type of particles (WIMP) because we cannot confirm thier existance. Maybe it`s time to look for other explanation: Chandra detected such halo but made of byronic matter.
Q-Star
2.6 / 5 (5) Oct 30, 2012
Maybe it`s time to look for other explanation: Chandra detected such halo but made of byronic matter.


Baryons are regular matter. You are made of baryons, if the dark matter were baryons, they wouldn't be dark. (Psst, every proton and neutron in the universe is a baryon.)
Fleetfoot
3.7 / 5 (3) Oct 30, 2012
That can't happen with dark matter, if a new particle was pulled by gravity towards a ball of particles, it would pass right through them. ...
In fact this is only hypothesis. We can observe efects caused by "dark metter" and it`s the only thing wchich is confirmed. We still don`t know what the dark matter is ...


That's correct but what we see in the Bullet Cluster is that the normal gas associated with the galaxies collided producing a cone-shaped pattern (pink regions) whereas the dark matter component passed through unaffected (blue):

http://apod.nasa....824.html

What I said above only assumes that behaviour is consistent.
radek
1 / 5 (3) Oct 30, 2012
Maybe it`s time to look for other explanation: Chandra detected such halo but made of byronic matter.


Baryons are regular matter. You are made of baryons, if the dark matter were baryons, they wouldn't be dark. (Psst, every proton and neutron in the universe is a baryon.)


That`s what I told - there`s no need to look for dark matter becausue such halo of regular matter surrounding Milky Way (huge cloud of extreme hot and diluted gas) was detected by Chandra
Q-Star
3 / 5 (6) Oct 30, 2012
That`s what I told - there`s no need to look for dark matter becausue such halo of regular matter surrounding Milky Way (huge cloud of extreme hot and diluted gas) was detected by Chandra


You are missing the point,,, no one is saying there is NO regular matter in galactic halos,,,,, it is not a new thing,,,, only there is no where nearly enough to account for the observations of the mechanics of the galaxies.

Chandrasankar would be one of the first to tell you that there is not nearly enough normal matter to explain the phenomena we see.
Fleetfoot
4 / 5 (4) Oct 30, 2012
Maybe it`s time to look for other explanation: Chandra detected such halo but made of byronic matter.


Baryons are regular matter. You are made of baryons, if the dark matter were baryons, they wouldn't be dark. (Psst, every proton and neutron in the universe is a baryon.)


That`s what I told - there`s no need to look for dark matter becausue such halo of regular matter surrounding Milky Way (huge cloud of extreme hot and diluted gas) was detected by Chandra


Science is quantitative, the amount found is a small fraction of the total required. If it was purely baryonic, the gravitational pink and blue regions here would be the same:

http://apod.nasa....824.html

If it was all baryonic, the CMBR angular power spectrum would be very different:

http://map.gsfc.n...dex.html
radek
1 / 5 (3) Oct 31, 2012

You are missing the point,,, no one is saying there is NO regular matter in galactic halos,,,,, it is not a new thing,,,, only there is no where nearly enough to account for the observations of the mechanics of the galaxies.

Chandrasankar would be one of the first to tell you that there is not nearly enough normal matter to explain the phenomena we see.


I`m talking about Chandra telescope

http://phys.org/n...gas.html

Astronomers have used NASA's Chandra X-ray Observatory to find evidence our Milky Way Galaxy is embedded in an enormous halo of hot gas that extends for hundreds of thousands of light years. The estimated mass of the halo is comparable to the mass of all the stars in the galaxy.

Fleetfoot - probably there`s another explanation of that phenomenon
Fleetfoot
4.2 / 5 (5) Oct 31, 2012
no one is saying there is NO regular matter in galactic halos ... only there is no where nearly enough to account for the observations of the mechanics of the galaxies.


The estimated mass of the halo is comparable to the mass of all the stars in the galaxy.


The mass of all the stars is about 5% of the total. If there is a comparable amount of baryonic matter in the halo, that still leaves 90% as dark matter.

Fleetfoot - probably there`s another explanation of that phenomenon


The Bullet Cluster demonstrates that two types of material are involved, one baryonic, the other not.

You can play with the uinverse builder applet to try to find an alternative set of parameters that match the observation but it is well known that the height of the third peak in particular is strongly driven by the non-baryonic content.

Overall, you have three entirely different observations all telling the same story with no real alternative for any of them. The conclusion is obvious.