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A Dark Flow in the Cosmos

Seeing things that are otherwise invisible means looking for their effect on the things we can see. Examples abound: The presence of dark matter was originally inferred from the shape of galaxies, and the fact that the mass of what we could see couldn’t explain how these cities of stars held together. Dark energy turned up through minute examination of supernovae, shaping the idea that the acceleration of the universe is an ongoing phenomenon. And now we have another unusual effect suggesting the presence of matter beyond the observable universe.

The work grows out of the study of some 700 galactic clusters whose X-rays, emitted by hot gases, cause measurable effects on photons from the cosmic microwave background. This is the Sunyaev-Zel’dovich effect, in which high energy electrons impart some of their energy to the CMB. A variant of the SZ effect helps us study galactic clusters in ways that now suggest the presence of inflation in the early universe. Thus Alexander Kashlinsky (NASA GSFC), who lays out the finding in this news release:

“The clusters show a small but measurable velocity that is independent of the universe’s expansion and does not change as distances increase,” says Kashlinsky. “We never expected to find anything like this… The distribution of matter in the observed universe cannot account for this motion.”

Kashlinsky describes the motion as a ‘dark flow,’ pointing out that it is constant out to at least a billion light years, and suggesting that it extends across the visible universe. The extraordinary period of inflation in the early universe, a provocative theory found in Big Bang models of the cosmos, would indicate that what we see in the sky is but a portion of a much larger picture. We may thus be looking at galactic clusters that are being affected by matter that has been pushed beyond the observable universe.

Image: Hot gas in moving galaxy clusters (white spots) shifts the temperature of cosmic microwaves. Hundreds of distant clusters seem to be moving toward one patch of sky (purple ellipse). Credit: NASA/WMAP/A. Kashlinsky et al.

So what is this matter? The tremendously challenging paper Kashlinsky and team are about to publish describes them as “…pre-inflationary remnants located well outside the present-day horizon.” That, of course, offers at least the possibility of examining some features of the cosmos before inflation actually occurred. The reference is Kashlinsky et al., “A measurement of large-scale peculiar velocities of clusters of galaxies: results and cosmological implications,” accepted for publication in Astrophysical Journal Letters and currently available online.

Comments on this entry are closed.

  • Mark September 24, 2008, 16:06

    How long do you think it will be until some “chicken little” points out that this effect was discovered just days after the Large Hadron Collider powers up and melts itself down? Some days I wish I was a physicist instead of a bike messenger.

  • Pointless Geometry September 24, 2008, 19:49

    More evidence that the known universe just keeps getting bigger – or is infinite ;-)


  • Ronald September 25, 2008, 5:10

    Fascinating! Possibly information from beyond the observable universe!

    Doesn’t this also pertain to the same issue as mentioned two days ago by James Essig in ‘Notes & Queries 22 September 2008’ and raised in my post of 28 August and Adam’s response, under post 2769 ‘Advanced Propulsion: The Next Steps’? There I ask some questions with regard to the possible size of the total universe as opposed to the observable universe.

  • Adam September 25, 2008, 6:23

    Wow! A super-Hubble flow… maybe. Seems there’s new life in cosmology yet.

  • Michael Spencer September 25, 2008, 7:32

    At some point in the far future, the observable universe will consist solely of the local group, and then of only our own galaxy. At that time an observer would find precious little evidence of a previous, and far grander, universe. How would that observer ever piece together our picture of the universe?

    Similarly, this ‘Dark Flow’ is fleeting and scant evidence of a true universe far stranger- and bigger- than we can discern.

    It’s stunning, really.

  • James M. Essig September 25, 2008, 8:08

    Hi Paul;

    This is a fascinating article.

    The possibility of the observational exploration of effects on the observable universe from entities or agents from beyond the observable universe seems to me a paradigm changer in the way we consider the observational limits of astronomy.

    Perhaps this really great attractor, for lack of a better word, is a black hole located beyond the observable universe with respect to Earth. However, I can imagine that such a black hole would have to be huge, at least several orders of magnitude above the mass of the Milky Way Galaxy. Another possibility is that the attracting agent or object is located in hyperspace or higher dimensional space and is pulling on the contents of our universe from within higher dimensional space. Such a possibility, upon further study of the motion stream of the contents of our universe, including the specific detailed patterns of such motion may help us under stand the topology of local higher dimensional space.

    Either way, the pace of observational astronomy and observational cosmology based discoveries seem to be really picking up. I am grateful to be living at a time of such great transitions in science and technology.



  • Ronald September 25, 2008, 10:47

    @Michael Spencer: yes, I know what you are referring to (described recently in Sientific American by Krauss & Scherrer “The end of cosmology”).

    However, from what I have understood about the expanding universe, our observable universe will consist of more than just the Local Group: it seems that all galaxies within a supercluster (in our case the Local or Virgo Supercluster) are gravitationally bound and cosmic expansion takes place beyond the level of supercluster. Within that supercluster, galaxies gradually merge to become one supergalaxy.

  • djlactin September 25, 2008, 12:37

    It’s the drain!

  • Pixie of key September 27, 2008, 12:14

    I predicted dark flow phenomenon already 28.5.2008


    The Google translation

    The baby Galaxies


    To links, where it is english


    Maybe these baby galaxies are from different energyconcentration than older galaxies. If so, then the baby galaxies could be moves to detect this.

    Both concentrations of energy, therefore, are located in the visible universe outside and they are expanded, and emit energy waves with a galaxy nature.

    Heitämpä So ilmoille suspicion here!

    Renovation Jukteri

    I made a YouTube video more than a year ago. It will tell why the dark flow is possible!


    important video


  • Robbb September 28, 2008, 23:50

    amatuer cosmologist here with a thought. the big problem with expansion theories is that we don’t understand how the universe could still be expanding b/c the observable mass doesn’t match what we’d expect.

    But if the universe is much larger than we can observe, with possibly a non-uniform distribution of mass, this could be the explanation, yes? Just trying to grasp this.

  • Ronald September 30, 2008, 4:54

    Robbb: fascinating idea, presently dark matter and dark energy fulfil this function. This is more or less also what I suggested in my post of 28 august (different thread, see above): could information about such a (much) larger total universe be derived from gravitational (and hence expansion rate) deviations, resulting from large mass acroos the ‘horizon’?

    Now indeed it seems like that.

  • robbb September 30, 2008, 10:57

    hi Ronald, thanks for your reply. i went back to read your other post as well, and Adam’s reply to that. i’m not bright enough to add anything additional ‘scientifically’, but the notion of a larger, possibly infinite universe that we may never be able to fully observe seems like it would really quake all the current theories, especially the troublesome dark energy stuff.

    i don’t fall in the ATM camp b/c i simply don’t know enough to have a strong opinion, but on a philosophical level i am intrigued at how the universe continually seems to surprise and baffle us as we learn more, and therefore discover how much more we DON’T know.

    a much much larger universe that is perhaps much much older than we will ever know tinkers with every notion we have about how the universe ‘began’, if there is even a start point to reference. and then of course we could go on and on about what this means to the idea of a Creator or Creators existing to create it.

    either way, it sure is interesting and makes the mind wander.

  • Pixie of key October 1, 2008, 3:48

    Dark flow phenomenon causing force drawing someone truly massive property is located in the visible universe outside? How does this tractive force is conveyed?

    For example, the stars radiate throughout the energy of waves with particles of nature! Particles moving mode, which is already in place and at the same time, the region can move particles emanating from the various starfish, and they continue the movement quite the same direction away from the area in which the stars is!

    The visible universe outside is truly massive concentration of energy which radiate energy waves, which have the nature of quasars. the same region can become the galaxy from several different angles, so that the business continues to quite the same direction, at the same time, when the first stars emit flammable Light. As a dark flow phenomenon can be explained logically!


  • ljk October 2, 2008, 23:04

    Hope fades for neutrino dark matter

    Physicists restrict the properties of ‘sterile’ neutrinos


  • ljk November 3, 2008, 10:22

    An article on Dark Photons:


    Which asks the question: Is there Dark Life too?