Dark Matter Thoughts

[alter-ego]

Thanks, Mark. I actually meant to post this Friday and it somehow got lost in the shuffle. When I saw your post I went looking for where I posted it, not to be found of course. I thought it was an interesting article. Here is the referenced paper:

Asymmetric Dark Matter and the Sun

• Physical Review Letters 105 011301 (02 July 2010) DOI: 10.1103/PhysRevLett.105.011301

It is an interesting idea. Unfortunately, I don't have online access to the paper, so a lot of details are missing. In particular, it isn't clear by what process the Sun would accumulate dark matter. You would not expect the Sun to encounter galactic dark matter with a relative velocity slower than the solar escape velocity. So most material should just pass through the Sun without being captured. Maybe I'm missing something with respect to how the dark matter interacts with itself (since dark matter particles are presumed to be their own anti-particles). I need to see the paper, or a bit better analysis of the work.

Try this arxiv.org version - it should reflect the June 1 revision published in July 2 PhysRevLett.
Asymmetric Dark Matter and the Sun (Frandsen & Sarkar)

[bystander]

Here is some more on the subject:

Heart of darkness could explain sun mysteries
New Scientist | Space | 14 July 2010

IS DARK matter lurking at the centre of our bright sun? Yes, say two research groups who believe the elusive stuff is cooling the solar core.

The insight doesn't significantly affect the sun's overall temperature. Rather, a core chilled by dark matter would help explain the way heat is distributed and transported within the sun, a process that is poorly understood.

Dark matter doesn't interact with light and so is invisible. The only evidence for its existence is its gravitational effects on other objects, including galaxies. These effects suggest dark matter makes up about 80 per cent of the total mass of the universe.

The idea that it might lurk at the heart of the sun goes back to the 1980s, when astronomers found that the number of ghostly subatomic neutrinos leaving the sun was only about a third of what computer simulations suggested it should be. Dark matter could have explained the low yield because it would absorb energy, reducing the rate of the fusion reactions that produce neutrinos.

However, the problem was solved another way when it was found that neutrinos oscillate between three kinds, only one of which was being detected on Earth. As a result, the idea of solar dark matter was dropped.

Now it is being resurrected in the light of recent searches for dark matter, which have put limits on the mass of the particles that it is made of and shown that it interacts only very weakly with ordinary matter. These led Stephen West of Royal Holloway, University of London, and his colleagues to explore what would happen if particles that fell within these limits exist in the sun.

Their simulations show that gravity would pull such dark particles to the centre of the sun, where they would absorb heat. Some of these dark matter particles would then carry this heat from the core to the surface, decreasing the core temperature

Observational constraints on supermassive dark stars

• arXiv.org > astro-ph > arXiv:1006.0481 > 09 Jun 2010 (v2)

[swainy]

Why don't Black Holes absorb Dark Matter?

I just asked this question on Google and got this answer:

http://www.universetoday.com/2010/03/22 ... rk-matter/

I think, If this is true, It will be monumental to understanding Dark Matter And Black Holes. How can this be? Gravity Is Gravity Huh?

Very Very Interesting.

tc

[Chris Peterson]

Why don't Black Holes absorb Dark Matter?
I just asked this question on Google and got this answer:
http://www.universetoday.com/2010/03/22 ... rk-matter/

That's interesting, and there may well be some truth there. But it seems obvious to me that black holes would tend not to absorb much dark matter. The only reason ordinary matter gets absorbed is because that matter interacts with itself and EM, creating drag and allowing it to spiral into the gravity well. Without drag (which shouldn't occur with dark matter), stuff will just orbit the black hole, not be drawn in. That's why black holes, even supermassive ones, don't suck up much material of any kind. It is only with a very high matter density- that is, close to the black hole- that you get the necessary drag to decay orbits.

[swainy]

And Then I found This!

Quote:

"24 trillion metric tons of dark matter lies between Earth and the moon. Such a dark matter halo might explain the anomalies seen in the orbits of the Pioneer, Galileo, Cassini, Rosetta and NEAR mission spacecraft, he adds."

http://www.scientificamerican.com/artic ... rcle-earth

tc

[Chris Peterson]

And Then I found This!
Quote:
"24 trillion metric tons of dark matter lies between Earth and the moon. Such a dark matter halo might explain the anomalies seen in the orbits of the Pioneer, Galileo, Cassini, Rosetta and NEAR mission spacecraft, he adds."

The idea that dark matter in the Solar System could produce observable effects is very interesting. But you did not accurately repeat the quote. It should be

"Based on current data, Adler estimates in the October 17 Journal of Physics A that at most some 24 trillion metric tons of dark matter lies between Earth and the moon."

That is quite a bit different.

[swainy]

It is interesting. Thanks Chris. I read on, and it says Dark Matter interacts with planets in a way that would explain other phenomena, Namely Heat. Quote: Adler also speculates that dark matter could exert dramatic effects on the four gas giants in our solar system—Jupiter, Saturn, Uranus and Neptune. If these massive worlds have gravitationally captured dark matter, then dark matter particles could smash into them—rare events but enough to heat up the gas giants and account for why the insides of these planets (and even Earth) seem hotter than known mechanisms can explain. It might also account for why Uranus seems anomalously cold—the planet is bizarrely tilted, perhaps because of a colossal impact, and Adler surmises that this collision might have knocked away most of the dark matter cloud that might typically have heated Uranus.

So Dark Matter really is Here all around us, But we can not sense it in any way. So what process creates it?

[Chris Peterson]

So Dark Matter really is Here all around us, But we can not sense it in any way. So what process creates it?

I think the general assumption is that it was created by some poorly understood process very early in the Universe, much as most ordinary matter was.

[trickstar]

Seems like a Klien's bottle mechanism for matter t-star

[bystander]

Does the sun hold a dark secret?
Royal Holloway University of London | 21 July 2010

[b][i](Credit: NASA/Goddard/SDO/AIA Team)[/i][/b]

---

A scientist at Royal Holloway, University of London believes dark matter is lurking at the centre of the sun and cooling down its core temperature.

The latest study, led by Dr Stephen West from the Department of Physics at Royal Holloway, looks at the possible effects of dark matter on the properties of the sun, if these elusive particles become trapped at its centre.

“Dark matter makes up more than 80 per cent of the total mass of the universe. We know that dark matter exists but to date it has never been produced in a laboratory or directly observed in any experiment, as a result we have very little information about what it actually is. It is important that we examine all possible ways of probing the nature of dark matter and the sun could provide us with an unexpected laboratory in which to do this,” says Dr West.

Dark matter is expected to form a halo around our galaxy and since the sun is in motion around the galaxy it experiences a dark matter "wind" as it moves through this halo. Some of the dark matter particles may collide with the elements in the sun and become gravitationally captured by the sun. This could lead to a build up of dark matter particles at the centre of the sun.

The research team’s simulations show that the effect of this build up is to reduce the temperature of the solar core. The dark matter particles can absorb heat at the core and transfer it out towards the surface, decreasing the temperature of the core. This change in temperature affects the number of neutrinos produced as by-products in nuclear reactions within the Sun and it is hoped that by examining these neutrinos we can gain information about the Sun's core temperature and whether dark matter plays an important role in solar physics. This in turn could provide information about the mass of individual dark matter particles and how they interact with the elements in the sun.

Dr West adds, “The next step in the work is to look more closely at the change in the predicted number of neutrinos produced in the sun as a result of dark matter collecting at the core and to examine the sensitivity of existing neutrino experiments to this change. In addition, an investigation of the possibility of probing this type of dark matter at the Large Hadron Collider is planned. The LHC could provide complimentary information about the properties of dark matter which along with the information from the sun may lead to a clearer picture of one of the more puzzling issues in physics.”