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This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters. Starlight from galaxies is indicated in orange. Green indicates hot gas, and blue indicates mass, most of which is dark matter.
Astronomers using the Hubble Space Telescope are mystified by a merging galaxy cluster known as Abell 520 in which concentrations of visible matter and dark matter have apparently come unglued.
A report on the Hubble observations, published in the Astrophysical Journal, raises more questions than answers about a cosmic pile-up that's occurring 2.4 billion light-years away.
"We were not expecting this," the study team's senior theorist, Arif Babul of the University of Victoria, said in a news release. "According to our current theory, galaxies and dark matter are expected to stay together, even through a collision. But that's not what's happening in Abell 520. Here, the dark matter appears to have pooled to form the dark core, but most of the associated galaxies seem to have moved on."
The dark core was first detected in 2007 during a survey aimed at measuring the masses of 50 galaxy clusters using data from the Canada-France-Hawaii Telescope at Mauna Kea in Hawaii.
The discovery presented the perfect opportunity to map the distribution of visible vs. dark matter in the cosmic mess. Studies have shown that we can see only about 15 percent of the matter in the universe. Most of the matter that exists around us can't be seen directly, but can be detected only by its gravitational effect. Scientists don't know what dark matter is, but they suspect it's an exotic class of subatomic particles that can interact only weakly with the kinds of matter we can see.
Dark matter is thought to provide the invisible "scaffolding" for structure in the universe, gravitationally binding galaxy clusters into a cosmic web. Those clusters get so massive that they bend the light of distant galaxies like a lens. By analyzing those subtle deflections of light, it's possible to come up with a map showing where the dark matter lies. That's what astronomers did with Abell 520 — first with the telescope in Hawaii, and then with the Hubble Space Telescope's Wide Field Planetary Camera 2.
The results contradict what scientists thought they knew about dark matter. In a previous study of the Bullet Cluster, 3 billion light-years from Earth, astronomers found that concentrations of dark matter blasted through the scene of a collision, with their associated galaxies tagging along. Meanwhile, waves of hot, X-ray-emitting gas clumped up in the middle.
In the case of Abell 520, the situation is completely different: The galaxies sailed through the collision, but the dark matter piled up in the middle, along with the hot gas.
Researchers were hoping that Hubble would resolve the mystery first posed by the detection of the dark core in 2007. No such luck.
"We know of maybe six examples of high-speed galaxy cluster collisions where the dark matter has been mapped. But the Bullet Cluster and Abell 520 are the two that show the clearest evidence of recent mergers, and they are inconsistent with each other," James Jee, an astronomer at the University of California at Davis who is the lead author of the Astrophysical Journal paper, said in a news release from the Space Telescope Science Institute. "No single theory explains the different behavior of dark matter in those two collisions. We need more examples."
Jee, Babul and their colleagues propose several possible explanations for the discrepancy. One explanation might be that the dynamics of the Abell 520 collision are more complex than the Bullet Cluster's crash. Maybe multiple collisions, involving three or four galaxy clusters, have led to the dark matter pile-up.
Another possibility is that there's actually lots of ordinary galactic material in the core, but it's just too dim to be seen, even by Hubble. That would suggest that the super-dim galaxies in the core have somehow formed far fewer stars than normal galaxies.
The most unsettling scenario proposes that there are different kinds of dark matter, and some of those kinds are "stickier" than others. Abell 520 might have a particularly sticky kind of dark matter that interacts with itself and clumps up like a wet snowball.
The astronomers behind the Abell 520 observations are now planning to run computer simulations of cluster crashes to find out whether there's an unusual set of conditions that could produce those observations and still fit current theory. "My colleagues tell me the likelihood is nil," Andisheh Mahdavi, a member of the study team from San Francisco State University, said in a news release, "but now we have the responsibility to go and do the hard work to check the simulations."
If the simulations aren't successful, the mystery might have to be left for particle physicists to mull over. Some hope that experiments such as Europe's Large Hadron Collider and the Alpha Magnetic Spectrometer, installed last year on the International Space Station, will eventually shed additional light on the dark matter mystery.
"I'm just as perplexed as I was back in 2007," Mahdavi said. "It's a pretty disturbing observation to have out there."
Update for 5:40 p.m. ET March 2: The picture of Abell 520 served as this week's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page this morning, and it took only a few minutes for Ryan Marquis to figure out what the image was all about. "It appears the dark matter and galaxies aren't anchored as previously believed," he wrote.
I'm sending Ryan a pair of 3-D glasses as a token of my appreciation. It turns out Ryan's a fellow space blogger who posts his items on 46BLYZ. We're glad to have him as a Cosmic Log correspondent, and hope that more of you will join our Facebook community. That's where you'll find the next "Where in the Cosmos" puzzle, a week from now.
Correction for 9 p.m. ET March 5: The original version of this item had the wrong first name for SFSU's Andisheh Mahdavi. I regret the error and extend apologies to the professor.
More about dark matter:
- Crazy cosmic lens focuses on dark matter
- The darkest mystery of them all
- Dark matter mapped in 3-D detail
- Gallery: Dark matter revealed!
- Search for dark matter on msnbc.com
- ... And what about dark energy?
In addition to Jee, Mahdavi and Babul, the authors of "A Study of the Dark Core in A520 With Hubble Space Telescope: The Mystery Deepens" include H. Hoekstra, J.J. Dalanton, P. Carroll and P. Capak.
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.
Leave a Comment:
I have some dark matter in my PANTS!
i blame hubbles standard candle thing, i think that sorting black and white photos to create a distance equivalence
is problematic.especially given the " primitiveness " of telescope and photography. and so much is postulated
from that construct......
wants a skeptical reworking from the ground up.
Simple, the Dark Matter/Energy models are wrong as is Einstein's General Theory on intergalactic scales. There are other theories out there that should gain momentum now.
Close your eyes. What do you see? Nothing right. Just because you can't see it doesn't mean it's not there. That being said. We are all so very ignorant. And that's not such a bad thing. It makes life interesting. Do I believe in the dark matter theory. I believe there is more to the universe than meets the eye. I believe that we are wrong more often than we are right. I never liked history all that much, but if you look at it, the farther you go back the more mistakes we find. It will be true of our present when others look back on us. For all we know the universe is no bigger than a drop of rain. Perception has us believe in the absence of light. Logic has us believe in the existence of emptiness. We are puppets pulling our own strings.
Please understand that this is in no way a scholarly, primary source for information. This is a popular, secondary source in which someone had a few hours or days to condense an idea that is barely come out of research labs for preliminary theory. So be patient and read some scholarly sources for better understanding.
MAybe those galaxies that have thrown off their dark matter will evolve without Republicans? Could that be heaven?
Another political spin. Ha ha ha. No I'm not a republican. I wish that this forum has an bot that baned people for a couple of days if specific words or phrases were used.
Whatever theories are made by the armchair critics, to be believable they would need to explain how the Bullet Cluster and Abell 520 can possibly have different signatures. Of the 3 theories given by the discoverers, only one poses a new type of matter. The second one states that the dark matter is actually ordinary matter that is just dim. The third one posits that there are tertiary galactic interactions, which does look the case, given the appearance of clustering of the blue and orange blobs.
Also, the Bullet Cluster also exibits separation of mass and observed light that hasn't been fully explained. If you haven't done it yet, watch the simulation at the link to the Bullet Cluster. It is a really sophisticated visualization, and might stimulate a brain cell.
A fourth possibility is that we are seeing a galactic rainbow caused by an inherent property of light or particles that are diffracting differently in Abell 520 and the Bullet cluster. This doesn't seem very likely, since this diffraction would have to occur at the scale of galaxies, but it seems better than some of the mutant zombie theories in these posts.
And a fifth possibility related to the first, third and fourth is that we are seeing an inherent property of known, but poorly understood energy that we didn't know about before, say an interference pattern in gravity waves that can only be observed at galactic scales. Or particles or neutrinos. Whatever. I like this theory because it could be acting at the scale of galaxies in a way that could explain the pattern of the blobs, but the details of how the galaxies collided could explain how there might be differential interactions at finer scales. It doesn't require exotic new types of matter, although it doesn't rule them out.
Could this potentially be particles forming in the wake of a galaxy passing through a cloud of material. We would be observing the coalescencing of particles that have been agitated together as a body paases nearby-loke the film on the rear of a van, or the cavitation effect with fluid mechanics where particles actually wear down a spinning object that passes through a mass.
Love this post by the way.
Dark matter does not exist. There are two types of gravity -- linear and circular -- but only linear gravity is known by our astronomers and that is why they are confused.
Surprisingly, there's no link to the "circular gravity" website here.
At some point, man will have to deal with "Wormwood..."
This is the most fraudulent astronomy image ever circulated.
Isn't there current observational data that suggests that interstellar planetary bodies outnumber stars something like 100,000 to 1? If that proves to be the case, why would you need any exotic form of matter to explain this kind of phenomena?
Generally when the observations don't agree with the theory, the first step is to check the measuring equipment. There are a lot of assumptions involved in trying to measure something this far away and even the idea of "dark matter" is simply speculation at this point.
Don't you love how so many in this forum think they are smarter than genius level astrophysicists? I find it quite amusing.
Perhaps some people think they have evaded obstacles to clear thinking which may be imposed by training in a rigorous discipline. That is, they think the cosmologists are so intent on competing within their own sphere that they can't see the forest for the trees, or at least that they may be barking up the wrong tree. They feel the scientists are trying to figure out how much wood a woodchuck would chuck if - and ONLY if - a woodchuck could chuck wood, without taking into account the very real possibility, even high probability, that a woodchuck does not - in fact cannot - chuck wood, given that he doesn't possess an opposing thumb which would allow him to grasp the wood firmly enough to chuck it, nor the kind of intention to interact with distant objects by the use of an intermediary medium, such as a chucked piece of wood. I, however am not of this particular school of thought, and believe the scientists are doing the best they can within a range of well-established parameters.
*Edit*
The phrase "intermediary medium" is obviously redundant; the word "intermediary" would have sufficed.
Doug-950479, did you stay at a Holiday Inn Express last night?
I hope you don't pull out that attitude with the doctor who is treating you for chest pains: "Doc, I know that many people in my situation are suffering heart attacks, but you are just stuck in your heart attack paradigm. I'm going to talk with my paradigm-free, non-doctor buds on the 'vine to figure out what is really going on with me."
Ben, I hope you know a joke when you see one, it helps in life
Dealing with a subject that is life threating I would expect but you to do, but I don't see the connection to what Ben said which I agree with.
I do, Doug, but what you have written is indistinguishable from the typical screed that gets posted on here. I prefer to make the waters clearer, rather than more muddy.
Noah R got it right way back at post 1.14:
Thanks, Noah. Most of you should have stopped right there. For those who didn't and desperately struggled to get your oar in the water with your own pet theories/ideologies/religions while calling the astronomers who actually study this stuff idiots, it has been an entertaining half-hour. I dedicate this next quote to you:
How many theories are still undiscovered? Compared to ones known. I'm an artist not a scientist and I just want to get perceptive.
We haven't even started yet. Even with all that we know (and may be rightfully proud at our accomplishment in starting to noodle out the Universe), we don't even know enough to yet grok the dimensions of the undiscovered ocean before us.
Cheers! ~Michael (Astronomy.FM★Radio)
Mikey, I'm afraid they don't grok GROK! (let's hope I'm wrong though!)
I bet that studio steve groks! Steve's and Stephen's grok more than the average citizen, in my experience.
Perceptive on Perspection, that is!
What is Perspection, is that a new art form?
This is just wrong! Can't dark matter and regular matter just get along! Segregation is wrong in all it's forms. What's next? We find a galaxy that's busing it's dark matter to another galaxy! I guess I'm naive to think the universe had moved beyond this after 14 billion years.
There's no place for racism in our Linfinite universe!!
I agree for all good law abiding particles. But those damn Tachyons and Neutrinos who think they are above the laws and can just do whatever the hell they please go too far. I'll welcome them when they obey the law and start interacting like any good normal matter, dark or otherwise! It's not racism. We have these laws for a reason!
Oh, and I thought we had stomped out all the Linsanity?
Brian-546328, You are a racist to the highest form. You will change your tune when a Tachyons and Neutrinos are needed to save your life.
Well I will admit that I have thought about building a wall around our galaxy but I know the Neutrinos would just go right through it and the Tachyons will just go back to a time before the wall was built. It's just not fair to all the matter that obeyed the laws to get to our Galaxy!
I've got a headache.
A simple explanation for the scientists making everything seem so complicatedand and mysterious is that it makes it easy to get a grant and funding from our leaders in Washington, thay don't have a clue to what is going on.
True, they just want to get elected. They're courting the dark matter vote right now
Well if the theories are correct then it's a smart move since dark matter is thought to be in the majority.
Most politicians have never heard of dark matter and wouldn't understand it if they did. Politicians do not decide who gets academic grants.
Funny, this only happens while Obama is president. The universe must not like Obamacare as well.
what if all the missing or "dark matter" is in black holes with nothing falling in so they don't emit the detectable phenomenon that has caused several black holes to be "discovered". They still act as mass and have massive gravitational effects but are otherwise undetectable. Maybe black holes are more common than previously thought. How much mass could be accounted for in a black hole that successfully swallowed it's own galaxy in its entirety, out drifting between other visible galaxies, taking up mass but undetectable. could explain much, but that is what theories are for, attempts to explain observations in a logical and rational manner until either proven to be correct, mostly correct, or completely wrong. Too bad the actual scientists won't read the comments on the article, I kinda doubt the article's author and/or publisher will even read the comments either.
How many planets are ejected during the formation of a solar system? How many dead stars are floating through space? For every gravitational lensing effect we notice how many don't get noticed? I don't think we have any solid theories or numbers for any of this. I still come down on the side of the simplest explanations are usually the correct ones but much smarter people then me have looked at these questions.
We are realising that there are more black holes, more rogue planets, and more dead stars than we thought, but scientists still think that does not account for most of the dark matter. I'm not entirely clear why, but that's what i hear; for some reason they don't think their can be that much baryonic matter.
The scientists are measuring the background gravitational effect of all the galaxies in the universe, this mesurment dosn't mean there is a dark matter that can't be seen. The same can be said for dark energy, they are measuring a concentration of all the stars in the universe that give off radiation and other rays such as gamma rays, so these measurments do not mean there is dark energy they call matter that can't be seen. An example is we can't see RF, radio frequency but it is all around us, it is the siginals that make our TVs and radios work. by that , it can't be called matter.
Radio telescopes 'see' RF. We have instruments that that pretty much cover the entire EM spectrum. What we don't have are any good instruments to 'see' gravitational waves although they are in the works. Our best right now are earth based and haven't really detected anything yet and probably never will unless a black hole happens to wander through the solar system.
I am sorry for the crack about washington. I wanted to be scientific. But it is true.
Basically what Dark Matter can be explained as is the remnant of the outer layer of energy that was present at precisely the moment the Big Bang occured. Dark Matter itself really doesn't have much energetic properties but because of the amount of Dark Matter present in the Universe means that it would have a significant amount of mass.
Think of Dark Matter in this manner. The next time you build a camp fire look at the wood that is left over. The remains of the wood in ash form in the fireplace is what remains after the fuel contained within the wood has been spent that has been consumed by the atoms within the wood heating up to a point causing the molecular structure of the wood to deteriorate releasing the stored energy potential that is going on inside of the of wood itself.
Once the energy has been released and the wood is no longer able to be converted into energy all that remains is the wood material that if picked up and weighed regardless of it not having very much energy left would still weigh a certain amount.
The same is true is with Dark Matter.
This is not based upon some high level physics degree. This type of information is taught at the high school level of science....
But then again if you wouldn't have dropped out of high school to smoke dope and made certain that you had an education then you would know what I am talking about.