Dark Matter's Profile Discovered?

pingbak writes "According to New Scientist, astronomers may have potentially discovered dark matter's EM profile (story). For the rest of us, this means astronomers may have just discovered all of the extra force holding the galaxy(-ies) together, which is not currently explainable though gravity and black holes at the center of universes alone. Since dark matter doesn't interact with ordinary matter, it's almost directly undetectable -- but now, physics and astronomy may just have had an awesome breakthrough. Nobel Prize material if it proves correct!"

Comments

Re:Electrons?

[BigBir3d]

I am sure that this is more due to the writer's lack of understanding of the subject, then to what appears to be grand jumps in logic. I am somewhat sure the language of the paper will be much more clear.

However, because dark matter "feels" gravity like ordinary visible matter, it is a fair bet that it clumps in the centre of our galaxy.

Previous statement makes no sense until it is explained later that they started down the course of thinking dark matter has a mass far less then previously postulated.

"Heavy dark matter particles would produce high-energy electrons," says Hooper. "Since it's difficult to imagine how they could be slowed to a standstill, we were forced to consider a surprisingly light dark matter particle."

By "light", the researchers mean one to 100 megaelectronvolts, which is between 1000 and 10 times lighter than a proton.

good description of the kinds of dark matter

[rsdavis9]

http://www.astro.queensu.ca/~dursi/dm-tutorial/dm0 .html

From the link above there is:
1. cold dark ordinary matter(baryonic)
2. Non baryonic(exotic) dark matter both hot and cold

The article seems to indicate wilp(weakly interacting light particles instead of (in addition to) wimps(weakly interacting massive particles. Wilp's are like neutrinos. We have not discovered any wimps yet.

Re:Electrons?

[Anonymous Coward]

Some references...astronomy.net and the referred to article

the draft version of their paper

[pbhj]

http://www.arxiv.org/PS_cache/astro-ph/pdf/0309/03 09686.pdf ... this must be a draft there's a typo in their ackowledgments (I checked all the equations and they look OK though ;0)>

Re:Electrons?

[KDan]

There are many reasons, but one which you might look at is the large amounts of radiation coming from the galactic nucleus. As you may know, electrons absorb radiation and gain energy (velocity) when they do so.

Another explanation, if you take away the radiation, would involve a huge fermi sphere of electons which would require that only very few of them are sitting in that big gravity well with no kinetic energy.

There are other reasons why electrons would be very unlikely to be found at rest at the galactic core, but I think these will do.

Daniel

/. already knew this

[darkpurpleblob]

Dark Matter's profile.

Re:Dark Matter Explaination?

[radtea]

There are in fact many dark matter problems. This work deals with galactic dark matter only, which could be solved by normal matter. This is not the case for dark matter problems on larger scales.

On scales larger than galaxies, we can see that galaxies and groups of galaxies appear affected by stronger gravitational forces than can be accounted for by visible matter, and on very large scales it appears that there is more gravity than can be accounted for by ordinary matter, period.

There are strict limits on the amount of ordinary (baryonic) matter that come from primordial nucleo-synthesis. In the early seconds after the Big Bang, the quark-gluon plasma cooled down to form baryons (protons and neutrons, to you.) Eventually (some seconds or minutes later) the baryons cooled down to the point where their average energy was low enough that when they ran into each other they tended to stick together rather than flying apart again.

The nuclei formed in these early times were: hydrogen (single protons), deuterium (p+n), 3He (p+n+n), 4He (p+p+n+n) and tiny amounts of lithium and above. As you can imagine, the ratios of hydrogen to everything else are critically dependent on the density of neutrons at the time these nuclei were forming: the more neutrons, the more heavy nuclei. We can infer from observations on stars fromed shortly (~millions of years) after the Big Bang what these ratios were, which tells us the density of neutrons and protons at that time. We also know the volume (curvature) of the universe at that time, and so can infer the total number of baryons in the universe.

There are not enough baryons to account for the gravitational (or gravity-like) forces acting at the largest observable scales. Ergo, something else is happening (or the observations are wrong, which is always a possibility.)

Given the number of dark matter problems, it is unlikely that one particle will solve them all, and quite possible that we are seeing the effects of quite different causes at different scales. This should not be a surprise. For example, we already see very different causes at nuclear scales vs. atomic scales vs planetary scales. It is possible that on galactic and size-of-the-universe scales different causes are at work as well, either due to hitherto undiscovered forces or equally unknown particles.

--Tom

Re:center of universes?

[dustmote]

According to my friend the physicist, every point is the center, from that point's frame of reference. (I should point out, of course, that he's a relativist, rather than dealing too much with quantum scales)