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‘Dark Flow’ Pushes Deeper into the Cosmos

When you’re studying galaxy clusters, it doesn’t pay to be in a hurry. Harald Ebeling (University of Hawaii) is an expert on the matter, working with a catalog of over a thousand such clusters in a new study of the so-called ‘dark flow,’ the apparent motion of galaxy clusters along a path centered on the southern constellations Centaurus and Hydra. Says Ebeling:

“It takes, on average, about an hour of telescope time to measure the distance to each cluster we work with, not to mention the years required to find these systems in the first place. This is a project requiring considerable followthrough.”

The study, led by Alexander Kashlinsky (NASA GSFC), relies on hot X-ray emitting gas within a cluster, which scatters photons from the cosmic microwave background. The wavelength of scattered photons then tells us something about the motion of individual clusters. This tiniest of shifts in the CMB’s background temperature in the cluster’s direction, known as the Sunyaev-Zel’dovich effect, is small enough that it has never been measured in a single galaxy cluster. That’s where the large number of clusters comes in. The researchers used a catalog of 700 clusters from a 2008 study and folded in another 700, along with results from the Wilkinson Microwave Anisotropy Probe. All of which is complicated enough without throwing in unexpected results.

You would assume that in relation to the CMB, all large-scale motion would be random, but the ‘dark flow’ appeared in the data in 2008, and the new study extends the motion to twice the distance previously reported. Kashlinsky says it persists to as far as 2.5 billion light years away, even if the direction of motion is now considered unresolved. “We detect motion along this axis, but right now our data cannot state as strongly as we’d like whether the clusters are coming or going,” says Kashlinsky, but the motion itself is what is controversial, suggesting structure beyond the visible universe that is pulling on matter that we can see.

Image: The colored dots are clusters within one of four distance ranges, with redder colors indicating greater distance. Colored ellipses show the direction of bulk motion for the clusters of the corresponding color. Images of representative galaxy clusters in each distance slice are also shown. Credit: NASA/Goddard/A. Kashlinsky, et al.

So now we can add the ‘dark flow’ to the other great ‘dark’ imponderables, like dark energy and dark matter. All, of course, are the subject of further investigation, and more on that tomorrow. For now, I see that the dark flow will be the subject of new studies with the latest WMAP data, along with information gleaned from the European Space Agency’s Planck mission, which is giving us another look at the microwave background.

The paper is Kashlinsky et al., “A New Measurement of the Bulk Flow of X-Ray Luminous Clusters of Galaxies,” Astrophysical Journal Letters 712 (March 20, 2010), pp. L81-L85 (abstract). See also this GSFC news release.


Comments on this entry are closed.

  • kurt9 March 11, 2010, 15:13

    There are theories based on fractal models that postulate that the universe is far bigger than is commonly thought and that it is far older than the 14 billion years or so commonly claimed by the current big bang theories.

    Heim theory also pastulates a much larger and older universe than is postulated by big bang theory.

  • James M. Essig March 11, 2010, 17:48

    Hi /Folks;

    This is really interesting. In essence, we can capture signals produced by effects, or as the result of previous effects beyond our light cone of the observable universe. The latest estimate for the age of the universe is 13.75 billion plus or minus 110 million years.

    Perhaps the study of such effects can blossom into a field of extra-light-cone-cosmic archeology. It would be interesting to see if other bulk mattergy streams are occuring in our universe. Perhaps refined red-shift measurement and statistical analysis of recessional velocities can find additional large flows.

    If would be interesting if this dark flow was due to a black hole with a mass of about 10 EXP 20 solar masses or so.

    Given that a black hole with a mass of the observable universe would just about equal the radius of the observable universe, inorder for the black hole idea to pan out, a 10 EXP 20 solar mass black hole would have a density of about {[10 EXP (23 – 20)] EXP 3 }/(10 EXP 3) times or one million times the density of the observable universe. The radius of such a black hole would be one thousandth the radius of the observable universe. If the black hole had a mass of 10 EXP 21 metric tons, the black hole would have a density of about {[10 EXP (23 – 21)] EXP 3 }/(10 EXP 2) times or about ten thousand times the density of the observable universe and the radius of the black hole would be about one hundreth the radius of the observable universe.

    I could see such blackholes producing such a relatively narrow although large differential mass flow in our visible portion of the universe.

    Now if these black hole are rotating, an awesome prospect of providing for a cosmic scale wormhole in the center which could open to cosmically far distant locations in our universe or perhaps open up into another universe may be in order. But this is a whole different topic.

  • george scaglione March 12, 2010, 17:15

    jim yes as you left off above,indeed a whole different topic,but… a fantastically wonderful open opportunity for those of us interested in moving about the universe.i am a lucky guy to be able to talk to so many advanced individuals who are thinking about so many advanced topics for ,how shall i phrase it!? literally going anyplace in the universe.makes the stuff i followed so markedly as a young man(when i was in high school) seem primative by comparisson.no doubt about that.respectfully to one and all your friend george

  • spaceman March 14, 2010, 3:15

    So, these measurements hint that something beyond the visible Universe is pulling on matter within the visable Universe. How far beyond the visible Universe are we talking about? and what might be the pulling agent (black holes, dark matter, cosmic strings)?

    I find this work interesting because it may lead to an estimate of how much Universe lies beyond the observable Universe. How many of you, myself included, have wondered for how many hundreds of billions or trillions of light years does the actual Universe extend? Dark flow measurements may help us put a lower limit on the size of the Universe beyond the visable part, I think.

  • Parmanello March 14, 2010, 18:56

    I could devour sheets of acid for a week and not imagine some of the utterly incredible consequences outlined in this article. The universe is an exquisite machine, drenched in possibilities and a generator of mind blowing scenarios. It is my great hope that the supremely talented scientific elite who thrive off the consumption of physical data will one day enrich mankind’s veneer of knowledge about the universe with the ultimate theory of everything.

    If everything can be decomposed into mathematics, this shouldn’t be an untenable goal.

  • Ronald March 15, 2010, 4:37

    Also see the earlier thread “Gravitational Lensing measures the Universe”.

    Could this method, or another, such as gravity measurements/gravity lensing, universe curvature measurement, …, give us an idea about the size of the *entire* universe?

    The only size estimates for the entire universe, that I know of, are purely theoretical and lower bounds (such as 10^23 to 10^26 times the observable universe, based on Alan Guth’s inflation theory).

  • Roger June 22, 2010, 9:01

    What if, as postulated by the string theory, the big bang was caused by membrane contact of two parallel string universes. Could our universe be moving in the direction of another contact. All matter in our universe rushing in to what essentially would become a black hole. Nothingness. Contact occurs and then another big bang?

  • Joe Zingher July 25, 2010, 23:03

    Couldn’t “dark flow” just be the result of 1) weaker gravitational forces as the galaxies spread apart + 2) solar winds pushing the galaxies faster and faster?

  • Petri Rissanen October 30, 2010, 13:53

    Can it be, that the cosmos rotates around its ‘axis’? The cosmos is so vast, that perhaps it just looks, that the dark flow seems to go towards one point, but ‘in reality’ it rotates. If there was ( before big bang) some kind of spin in progress, there should be some kind of leftover momentum, which makes the whole universe go around?

  • Reelsmart January 6, 2011, 21:34

    Dark flow attraction is said to be coming from a distance of 1000 universes. Since gravity is subject to the inverse square law this implies a force moving some of our galaxies, themselves consisting of hundreds of billions of stars, that is only 1/millionth of what it is at it’s origin. Now that is some force !
    Note: very odd that this astounding conjecture comes from measurements that cannot tell if the galaxies being effected are coming or going !

  • kel August 21, 2011, 17:29

    i like PETTRI RISSANENS’ theory of a rotating universe though i am aware it has been postulated before. if the fingerprint of quantum mechanics can be stretched by inflation across the heavens so might rotation though i am not sure where this intrinsic rotation may originate. one thing however that is becomming appreciably apparent is the widespread acceptance of the “metaverse” theory and that what is observable is but a fraction of a fraction of what may be reality. kind regards to all, kel.