Dark matter is held together by 'attractors'

Dark matter is held together by 'attractors'
The dark matter structures are simulated in a supercomputer. The figure shows that the density of the dark matter is greatest in the inner part and slowly decreases as one moves towards the surface.

The universe consists of a large amount of invisible matter - dark matter. We do not know what it is, but we know that it is there and that without dark matter there would be no galaxies, and hence stars, planets and life as we know it. The universe is filled with large structures that are dominated by dark matter and in these dark matter spheres or 'halos' the light emitting particles form stars and gas clumps. Recent studies show that these dark matter halos have so-called attractors, which preserve their shape. The results are published in Astrophysical Journal Letters.

"It is somewhat surprising that we do not understand why these dark matter halos look like they do. The dark matter particles only feel the pull of gravity so it should be simple to find out, for example, how their density changes when you move from the inner to the outer part. But no one has yet understood why the temperature and density of the dark matter has the form we observed", explains astrophysicist Steen Hansen, Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Furthermore, it is not known whether there is a fundamental reason for the simple structure of the temperature and density of the halos, which are observed or whether their form is determined by the collisions and dramatic events they have been exposed to in the history of the universe, almost randomly.

Stars behave characteristically
As a star evolves you can measure its surface temperature and luminosity. Nearly all stars that are in the process of burning off their hydrogen fall into a main sequence with uniform states. This uniformity is an attractor for ordinary luminous particles because there is always a unique balance between radiation pressure and gravity as the fuse together to form helium.

If you take a star on the main sequence and 'knock' on it, so that it, for example, shines brighter for a short period than what the main sequence attractor says it should, (such a controlled change in conditions can be simulated on a computer, for example, by moving the energy in the star around a bit) then the star rushes back to the main sequence. This is characteristic for all attractors in nature.

Dark matter also behaves characteristically
Dark matter particles have no , so it was previously entirely unknown whether they could have a similar attractor and thereby explain why all of the dark matter halos look virtually the same.

"We have for the first time, through computer simulations, shown that dark matter halos have an attractor. We have found a very special relationship between the state of the temperature and the density of the dark matter from the inner part of the halo to the outer part," explains Steen Hansen, who has made the calculations together with two of his students, Diana Juncher and Martin Sparre.

The researchers created computer models of a wide range of different dark matter halos, all of which were in perfect balance. Then they 'knocked on' these structures so that they changed. They did so by moving the energy in them around a little bit, which you can do to stars in a computer model. But it turned out that all of the halos changed their state towards the same uniform shape. In this way dark matter halos are completely distinct from stars.

"When a star has exhausted its hydrogen, it moves away from the main sequence - it leaves its attractor. Since we have no indications that emits radiation or collide with each other, we believe that these halos will remain on their attractor forever", concludes Steen Hansen.


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Source: University of Copenhagen
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Aug 10, 2010
But no one has yet understood why the temperature and density of the dark matter has the form we observed
Here's the reason why. See the Evidence page:-
http://www.presto...ndex.htm

Aug 10, 2010
Here's the reason why
Actually from your explanation should follow, the dark matter is forming hallo with the central hole around massive objects - which is what has been actually observed by F.Zwicky already. The dark matter clouds forms a blobs only when being formed with itself - which is relatively rare case of the dark galaxies.

http://www.techno...sNum=341

Aug 10, 2010
Sorry Jigga please explain

Aug 10, 2010
If dark matter has an antigravitating effect, it should be repulsed by massive objects (actually I believe its net effect between galaxies results into dark energy, i.e. acceleration of Universe expansion observed). This is for example why I don't believe in hypothesis, dark matter affects the heat spreading inside of Sun - the concentration of dark matter should be lower there, then above Sun surface.

Actually it was observed already at the case of large galactic clusters, dark matter is forming rings around core of clusters, so that the above picture doesn't describe real situation well.

http://hubblesite...17/full/

Aug 10, 2010
The article would be less confusing to some if it was worded this way:

Dark matter is held together by 'brane attractors'

Aug 10, 2010
Or maybe: Strange Brane Attractors

Aug 11, 2010
Theory. Theory of dark matter. Theory of dark energy. Theory Theory Theory.

We KNOW very little about our universe, particularly the part outside our own solar system.

Aug 11, 2010
Adherents of dark matter have a big problem in that it cannot be seen, touched, felt etc. They've got a theoretical model which predicts certain behaviours for stars, planets and galaxies and now that those bodies do not conform to the theory some immeasurable explanation is called into being.
That way no one can dispute it and the believers can go on forever making loads of money out of it -ok, at least make a decent living off it. Well, maybe it's not such a big problem after all!

Call me skeptical if you want. I suspect the dark matter and energy will go away when someone introduces a much improved model for the behaviour of the universe.


Aug 11, 2010
"The Universe is not required to be in perfect harmony with Human ambition" Carl Sagan - It is "...Full of Magical things patiently waiting for our whits to grow sharper" Eden Phillpots. I keep these two quotes in mind always. I feel we will be stumbling around in the dark (no pun intended) for quite a while longer. Sooner or later though, someone will find the light switch and all will be revealed... a G.U.T. It only takes one person (or small group) to find the switch. I think the more people searching and the more ideas, the better (all metaphorically speaking of course). Whether Dark Matter & / or energy turn out to be correct is beside the point, they are still important seps on our continuing journey of understanding.

Aug 11, 2010
@Sazzle

Great quotes! Also great comment on the article as well!

Aug 11, 2010
Theory. Theory of dark matter. Theory of dark energy. Theory Theory Theory.

We KNOW very little about our universe, particularly the part outside our own solar system.


Is that a proven fact or a theory of yours?

Aug 11, 2010
This stuff reminds me of the story about the blind men and the elephant. Physicists feel this and infer that, they feel that and infer the other, etc. But are they inferring the Elephant and is it really in the room?

Aug 11, 2010
Because

Aug 12, 2010
Now I would like an explanation how this colourful isotropic sphere produces the rotation curve of the local galaxy.

Does any modified gravity theory provide an explanation?

Aug 12, 2010
Does any modified gravity theory provide an explanation?

Yes, for example STVG: http://www.newsci...ter.html Actually it's rather description, because no modern gravity theory explains gravity as such.

Aug 12, 2010
Now I would like an explanation how this colourful isotropic sphere produces the rotation curve of the local galaxy.

Your question could have more than one answer.

Aug 12, 2010
Adherents of dark matter have a big problem in that it cannot be seen, touched, felt etc. They've got a theoretical model which predicts certain behaviours for stars, planets and galaxies and now that those bodies do not conform to the theory some immeasurable explanation is called into being.
That way no one can dispute it and the believers can go on forever making loads of money out of it -ok, at least make a decent living off it. Well, maybe it's not such a big problem after all!

Call me skeptical if you want. I suspect the dark matter and energy will go away when someone introduces a much improved model for the behaviour of the universe.


http://www.apostr...p_02.jpg

We can see it. Here's a map of it.

Aug 13, 2010
No, we can't see it and that link doesn't show a map of DM. Instead it is a visualization of an universal DM distribution development. Based on 3 "time shells". Based on measurements of gravitational lensings which assume the validity of GR out there and back then as well as no extra-dimensions.
Which is why

That is a map of the distribution of dark matter as collected by the compiled measurements of grvitational lensing. So technically, yes, we can see its presence.

There was a great Nova episode on DM and the Morgan Freeman "Through the Wormhole" did a great layman's writeup on it.

Your points hold merit but assume we're entirely wrong, (could be the case), but the observational evidence is mounting. Some of those who deny dark matter also denied neutrinos until we reported catching a few of them.

Aug 13, 2010
PhysicsWorld.com has an article about dark matter dated today Friday August 13, 2010 titled: US astronomers unveil 10-year plan.

Link: http://physicswor...ws/43475

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