Direct proof of dark matter published

[Tormod]

Dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies. The discovery, using NASA's Chandra X-ray Observatory and other telescopes, gives direct evidence for the existence of dark matter.

 

lefthttp://hypography.com/gallery/files/5/1e0657_thumb.jpg[/img]"This is the most energetic cosmic event, besides the Big Bang, which we know about," said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

 

These observations provide the strongest evidence yet that most of the matter in the universe is dark. Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision.

 

"A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists."

 

In galaxy clusters, the normal matter, like the atoms that make up the stars, planets, and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and can only be detected through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart.

 

The team was granted more than 100 hours on the Chandra telescope to observe the galaxy cluster 1E0657-56. The cluster is also known as the bullet cluster, because it contains a spectacular bullet-shaped cloud of hundred-million-degree gas. The X-ray image shows the bullet shape is due to a wind produced by the high-speed collision of a smaller cluster with a larger one.

 

righthttp://hypography.com/gallery/files/5/1e0657_lens_ill_thumb.jpg[/img]In addition to the Chandra observation, the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope and the Magellan optical telescopes were used to determine the location of the mass in the clusters. This was done by measuring the effect of gravitational lensing, where gravity from the clusters distorts light from background galaxies as predicted by Einstein's theory of general relativity.

 

The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.

 

"This is the type of result that future theories will have to take into account," said Sean Carroll, a cosmologist at the University of Chicago, who was not involved with the study. "As we move forward to understand the true nature of dark matter, this new result will be impossible to ignore."

 

This result also gives scientists more confidence that the Newtonian gravity familiar on Earth and in the solar system also works on the huge scales of galaxy clusters.

 

"We've closed this loophole about gravity, and we've come closer than ever to seeing this invisible matter," Clowe said.

 

These results are being published in an upcoming issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass.

 

Source: Chandra Observatory

[cwes99_03]

Anyone care to decipher this a bit more. My mind is spinning trying to understand all that is presented.

[EWright]

Anyone care to decipher this a bit more. My mind is spinning trying to understand all that is presented.

 

It's called speculation and justification for 100 hours on an expensive telescope and going in with full intent to show evidence of what they were seeking in the first place. They'd find a way to attribute any anomaly to dark matter.

[InfiniteNow]

They'd find a way to attribute any anomaly to dark matter.

And what do you propose would be an acceptable alternative to this conclusion?

[cwes99_03]

Before we get into that, please try to restate the findings a little more clearly. How do they justify saying dark matter exists? What particularly did they discover in the data that proves its existence? Otherwise I'm going to have to find the answer myself by google. :)

[EWright]

And what do you propose would be an acceptable alternative to this conclusion?

 

It is not up to the jury to render a conclusion... it is up to those presenting their case to prove it is correct. Given the information in the article, to say

This proves in a simple and direct way that dark matter exists.

simply falls far short of actual "proof".

 

Dark matter is considered to exist in order to explain the way gravity is able to hold a galaxy together considering that it's rotation should cause it to fly apart. Scientists believe more matter is needed to hold the galaxy together, but they can not detect it, so they've attributed it to dark matter. This observation only shows an unexplained phenomenon that may be at least partially caused by gravity. This does not mean that dark matter is at the root of this explanation.

 

Scientists granted 100 hours of expensive telescope time, who said they were looking to this phenomenon as evidence of antimatter could express the identical argument as evidence of matter-antimatter annihilation and it'd be a more believable argument at that.

[Tormod]

I'd like to point out that 100 hours of observation is plenty to study something, and I would be very surprised if anyone had been granted 100 hours of observation time to "look for nothing". These people have been working on a theory for many years and when the observations match their prediction, this implies that we're seeing good science.

 

And frankly, people, you're commenting a press release and not the scientific papers.

[EWright]

I'd like to point out that 100 hours of observation is plenty to study something, and I would be very surprised if anyone had been granted 100 hours of observation time to "look for nothing". These people have been working on a theory for many years and when the observations match their prediction, this implies that we're seeing good science.

 

And frankly, people, you're commenting a press release and not the scientific papers.

 

Agreed, we're going off of the articles and not the direct scientific papers and data. I read the article here and the one at Space.com. I find it frustrating that SO often these types of articles are published as absolute truth, rather than a possible step in the right direction.

 

Granted, 100 hours is plenty of time to study something. But it could take 100 years of study to really pinpoint what dark matter is and whether it actually exists at all. Again, my main frustration is the presumptuous tone these type of articles so often take. I believe this study could LEAD toward a better understanding of dark matter IF it exists and that it offers good reason to continue the quest to understand the nature of dark matter or the cause behind it. But I just don't feel they've proven anything regarding dark matter so far.

[Tormod]

Again, my main frustration is the presumptuous tone these type of articles so often take.

 

I suggest reading the comments by the scientists here:

 

http://www.chandra.harvard.edu/photo/2006/1e0657/qa.html

[cwes99_03]

I suggest reading the comments by the scientists here:

 

http://www.chandra.harvard.edu/photo/2006/1e0657/qa.html

 

Tor, I have to believe that that link really just supports Ewright.

 

The very first Q&A suggests that they have no direct proof. Instead they operated on the idea that they know what dark matter is and then said that based on their definition of what dark matter is (which was completely arbitrary as he notes in the next Q&A) they saw the evidence that it existed.

 

 

The first answer to the first question is:

We then overlaid the X-ray image on an optical image, noticed the offset between the galaxies and the gas, and realized that this cluster offers a unique experimental setup for dark matter studies -- we only needed to map its dark matter distribution.

How do you map the dark matter distribution, when you don't have a clear understanding of what dark matter is?

 

The second answer to the second question shows that those questions are justified:

The nature of dark matter is one of the most important topics in astronomy, so everybody is interested. Little is known about it -- all that the numerous searches for dark matter particles have done is ruling out various hypotheses, but they never got any "positive" results. So any new piece of evidence is valuable.

 

Then later they make this funny statement:

Since the DM concept is so well-established, it means little in practical terms. For example, searches of dark matter particles have been going on before and will continue. However, such proof is important for our general understanding of the universe, because it gives us confidence in our basic assumptions. We all know of numerous examples in the history of science when a well-established theory turned out to be wrong.

What is so well established? How is it proof on your basic assumptions when you are just saying that your basic (unfounded) assumptions prove it's existance?

 

The article needs more depth and explanation, or else it is just HYPE. Hype does not make a good article. A good article has the who, what, when, where, why, and HOW answered. I see a who, when, and where, but no conclusive what, why, or how.

[Tormod]

I posted it because I thought it was funny, not because it's good. I agree that their statements are more bewildering than anything else - but it also shows that these guys are not presumptuous, which is what EWright claimed.

[Tormod]

How do you map the dark matter distribution, when you don't have a clear understanding of what dark matter is?

 

I have not read their paper, which I assume nobody else here have yet either, but we can accurately map the effects of gravity without having a clear understanding of what gravity is, so I don't think that's a fallacy here.

[EWright]

I have not read their paper, which I assume nobody else here have yet either, but we can accurately map the effects of gravity without having a clear understanding of what gravity is, so I don't think that's a fallacy here.

 

Please understand that I'm not trying to be argumentative here. However, we have gravity here in our own solar system without the need for dark matter, and it took centuries to accurately explain such things as the rotation of planets (pre-Newton, retrograde motion, etc.). I have trouble with the concept of defining so-called dark matter outside of the relm of its grravitational influence on galaxy rotation, since that the very basis of the concept of dark matter.

 

As far as the observations they made, they could argue that the void they witness or the "drag affect" are caused by dark energy. There's supposedly a whole lot more of that in the universe than dark energy.

 

And no, I too have not read their actual papers on this subject. If anyone knows where to access them online and can post a link, I'd be happy to take a look. Again, I'm not trying to be condesending or argumentative, I just feel the articles we've see thus far fall painfully short, and that titles including phrases like "Direct proof of..." are very misleading and seem to be becoming more common.

[Tormod]

I agree. It can seem as a quick jump to conclusions. There is a lot of research behind these results, though. I'll try and see if I can locate the actual papers.

[Tormod]

I guess we'll have to wait since the article states that "These results are being published in an upcoming issue of The Astrophysical Journal Letters.". :)

[cwes99_03]

As far as the observations they made, they could argue that the void they witness or the "drag affect" are caused by dark energy.

 

I thought that too, but the articles I keep reading say that the drag is not caused by the dark matter, but by the collision (gravity of the objects they are colliding with causing "drag".) And then they say that the dark matter is not feeling the effect of the "drag" of the collision, and they reason this is because it is believed the dark matter is non interactive except with gravity, and then you see the cunundrum, because if it only intereacts with gravity, then it should feel the same gravitational drag. Thus we are back to my original post on this article. Could someone please clear this mess up?

 

This btw is not Tormod's fault. There are dozens of articles out there and not one of them says it any more clearly than the article here on Hypography.

[C1ay]

I just feel the articles we've see thus far fall painfully short, and that titles including phrases like "Direct proof of..." are very misleading and seem to be becoming more common.

I'll second that. It kind of indicates that some conclusion has been drawn when there is really not enough evidence to draw an absolute conclusion....