Dark matter mapped - First three-dimensional picture of elusive matter throws up mystery.

news@nature.com ^ | 7 January 2007 | Katharine Sanderson

[neverdem]

Close window

Published online: 7 January 2007; | doi:10.1038/news070101-7

Dark matter mapped

First three-dimensional picture of elusive matter throws up mystery.

Katharine Sanderson

Concentrations of dark matter (mapped in contours above) usually - but not always - match up with normal matter (coloured).

Hot on the heels of evidence last year that dark matter really does exist (see 'Dark matter spied in galactic collision'), the same technique has been used to map this uncharacterized mass across half a million distant galaxies.

The map shows that, as predicted, the mysterious dark matter that makes up a quarter of the Universe forms a filamentous 'skeleton' upon which visible matter congregates, eventually producing stars. This is the first time such a large-scale three-dimensional picture of dark matter has been produced, and it will allow cosmologists to probe deeper into the nature of this elusive matter.

But the map, published in Nature¹, also has a few puzzles within it. Some areas show clumps of dark matter that aren't accompanied by the bright features associated with conventional, visible material (made of baryonic matter), and vice versa.

"On the large scale the general picture is as expected, but there are some small-scale discrepancies," says Richard Massey at the California Institute of Technology, Pasadena, and one of the team members who pieced together the map from hundreds of slightly overlapping images from the Hubble Space Telescope's Cosmic Evolution Survey (COSMOS).

The existence of large clumps of isolated dark matter and visible matter flies in the face of everything we know, says cosmologist Carlos Frenk of the University of Durham, UK.

The discrepancies could be a simple error resulting from the way the observations were made. But if they are real, says Massey, they will bring a huge shock. "Baryonic structures are expected to form only inside the dark-matter scaffold," he says. "There will need to be a lot of follow-up work before we really believe any individual discrepancies."

A light pull

Massey used a technique called gravitational lensing, whereby the pull from dark matter caught in between a star and the observing telescope alters the path of the light, and allows the presence of dark matter to be inferred.

Eric Linder of the University of California, Berkeley, who was not involved with the work, agrees that the map backs up the favoured theory that dark matter forms a scaffold on which galaxies form.

He suggests possibilities for the more unusual spots in the map: one is that galaxies made of dark matter (dark galaxies) exist, but he thinks this is unlikely. Another possibility is that the discrepancies are errors in the data — which seem almost inevitable given that mapping the dark matter required a very sensitive measurement of an incredibly small signal. "Right now the discrepancies are curiosities rather than items of concern," Linder says.

Massey is also confident in the robustness of his map on the whole. "A couple of individual discrepancies in the map are not a huge surprise," he says. "The technique is intrinsically more noisy, and more prone to systematic errors, near the edges of the map." That is where most of the discrepancies are seen.

Blown away

There are plausible explanations for small areas of dark matter and visible matter existing in isolation.

Dark matter, if the clump is small enough, could have any accumulating visible matter blown out of it by a high-energy phenomenon such as a quasar or a supernova, for example. The collision of two galaxies could also blow an amount of visible matter out as a faint satellite galaxy that has no associated dark matter, suggests Frenk.

But these theories can't explain the large features visible on the COSMOS map, he adds.

Like Massey and Linder, Frenk also suspects that the discrepancies are due to errors: "We know too much about the Universe," he says, to have completely missed this phenomenon up till now.

Visit our newsblog to read and post comments about this story.

	Top

References

1. Massey R., et al. Nature, advance online publication, doi:10.1038/nature05497 (2007).

	Top

Story from news@nature.com:
http://news.nature.com//news/2007/070101/070101-7.html

		© 2006 Nature Publishing Group | Privacy policy

[Southack]

"That's exactly what astronomers see. This study has anomalies because of errors. That anomalies increase toward the edges of the field confirms it."

#1, astronomers don't see "dark matter." It doesn't even exist.

#2, the study has errors in it because it is based on a pre-conceived notion (e.g. "dark matter") that is itself in error.

Errors beget errors. No doubt some drug-addled grad student will be coerced to fabricate some silly new "model" that supposedly rectifies the errors visible in the map displayed with the article for this thread, however, as "dark matter" proponents are not going to quit lying (to themselves as much as to the public) anytime soon.

[Southack]

"Local spacetime is bound by gravity. There is enough mass in your average galaxy to create a gravity well that prevents expansion. Molecules are even more absurd."

Flamboyant, ridiculous supposition on your part. Shame on you.

You have no evidence, no proof, not even a *hint* that Gravity prevents the fabric of space, dimensions themselves, from expanding in local areas...yet you spout such rubbish as if it was fact. It's not.

Nor can you even show a Force that *is* causing Space to expand.

Shame. Shame. Shame on you.

[commonguymd]

yes

[null and void]

Or where Hillary!™'s heart is supposed to be.

[RadioAstronomer]

You really need to study GR and SR.

You have no idea what you are talking about.

[RightWhale]

the fabric of space, dimensions themselves

There are three dimensions

Time, people, and dinner.

[Southack]

Oh please. You're just posting cop outs.

The plain truth is that you made claims that you can't substantiate.

Can Gravity prevent Space from expanding as you claimed was fact?

We don't know.

Is there a Force that is causing Space to expand as you claimed?

We don't know.

I take issue with your hubris and arrogance, and your repeated posts to me that either *I* don't know something or that you don't have time for this or whatever just goes to show that you are out of your depths in this field, capable of little more than spouting politically correct rubbish.

Because if you are capable of more than spouting such PCisms, you would have shown the Force that you claim is expanding Space...and you would have shown the evidence that we have in hand that shows that Gravity prevents Space from expanding locally.

But you haven't.

And you can't.

Shame on you. None of what you've spouted so far is the least bit scientific.

None of it.

Show the Forces that you claim as fact. Show the evidence.

[Southack]

For the lurkers on this thread, please keep in mind that Gravity is the **weakest** of all known forces.

There are dangerous know-nothings on this thread who would have you believe that the **weakest** of all Forces is capable of doing something that the strongest of Forces can not: expand Space.

[Southack]

...or stop the expansion of Space.

[Psycho_Bunny]

I've wondered that myself....only not that the matter was of "other universes" but rather, matter from our universe that was knocked slightly out of our reality by something like the Big Bang.....perhaps the first quarter of the matter of our universe was on the outer shell/fastest part of the explosion - moving so fast and under so much pressure that it moved slightly out of phase with the rest of the matter.

I've wondered too if dark matter could be the ejecta of black holes, similarly knocked our of phase by gravity.

I'd like to see the question of dark matter figured out before I die.

[Psycho_Bunny]

Utter nonsense. If "space" was expanding then molecules would be growing larger.

Um.....no. They wouldn't be.  They'd be expanding apart.

But, if they were growing larger, you'd wouldn't know it, and there'd probably be no way at all to see it happen.

 

[OrioleFan]

It looks like what you get when Algore's low flow toilet backs up.

[longshadow]

Please don't feed the Narcissist....

;-)

[PSYCHO-FREEP]

Surely you must have an understanding of the three components that are currently accepted as the standard model of the Universe?

You are missing one key factor that gives this theory it's feasibility.

[muawiyah]

The majority of folks on Earth actually believe you "com back" one way or the other ~ if they're correct it's likely the answer is going to be available for you someday.

[RadioAstronomer]

There are dangerous know-nothings on this thread

Hmmmm...some with PhDs in physics. No nothings indeed. /sarc.

[RadioAstronomer]

LOL!

[commonguymd]

http://news.bbc.co.uk/1/shared/spl/hi/pop_ups/07/sci_nat_enl_1168021092/html/1.stm

http://news.bbc.co.uk/2/hi/science/nature/6235751.stm


Neat 3-D version

[Fester Chugabrew]

If "space" was expanding then molecules would be growing larger.

If everything is relative that may be the case.

[RadioAstronomer]

Except that is not the case.