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  1. #1
    Sam Wormley's Avatar
    Sam Wormley Guest

    Default The Mother of All Pileups [suggests dark matter's hand]



    The Mother of All Pileups
    http://sciencenow.sciencemag.org/cgi...ull/2009/417/2

    By Phil Berardelli
    ScienceNOW Daily News
    17 April 2009

    In a faraway corner of the universe, a crash of cosmic proportions is under way, cramming
    more than 1000 galaxies into a space normally reserved for a handful. It's also
    compressing and heating enormous quantities of intergalactic gas. Astronomers studying the
    phenomenon say what they learn about the pileup should improve their understanding about
    how the largest structures in the cosmos have evolved.

    Our solar system sits in a quiet corner of a large, but otherwise ordinary--and
    solitary--galaxy. But in many other parts of the universe, things aren't so quiet.
    Collisions between galaxies and even clusters of galaxies are surprisingly routine. But
    the event called MACSJ0717 is a horse of a different color. Discovered in2003 and located
    about 5.4 billion light-years away, it involves four distinct clusters ofgalaxies
    converging along a filament of galaxies, gas clouds, and, mainly, dark matter that's about
    13.5 million light-years long. (For comparison, the distance between our Milky Way and its
    nearest neighbor, the Andromeda Galaxy, is about 3 million light-years.) Such filaments
    are thought to permeate the universe and to draw in galaxies and intergalactic gas clouds
    from less dense regions.

    It took a while to identify the filament, explains astronomer and co-author Harald Ebeling
    of the University of Hawaii, Honolulu. At first, he says, x-ray surveys of the clusters
    "showed just a mess, and the optical image didn't look much better." The problem, Ebeling
    says, was that the system of galaxies did not have a well-defined center,and the features
    in the x-ray images, which showed the distribution of hot gas, didn't seem to match the
    distribution of the galaxies. "We scratched our heads for a long time over this one," he
    says. "What exactly was going on here?"

    Further observations by lead researcher Cheng-Jiun Ma provided the critical clue: The
    temperatures of the constituent gas clouds--whose collective mass far outweighs the
    galaxies--suggested that the researchers were looking at multiple clusters colliding. "The
    pieces began to fall into place," says Ebeling, who with Hawaii colleagues Ma and
    Elizabeth Barrett published the findings last month in The Astrophysical Journal and
    released a composite image of MACSJ0717 yesterday. Ebeling says Ma's comparisons of the
    temperature peaks of the gas and the galaxy distributions enabled the team to deduce the
    directions of motion of the clusters.

    "Voil├*!" Ebeling says. "Not only did a consistent 3D picture of thiswild merger appear,
    but it also pointed conclusively toward the filament as the common sourceof all the
    mayhem." That discovery means theorists have been right about the role offilaments in
    funneling matter in the visible universe. If confirmed, Ebeling says, thefilament shaping
    MACSJ0717 could provide astronomers with a unique opportunity to measure the key
    properties of these cosmic highways.

    Finding a triple merger is extremely rare, says astrophysicist Craig Sarazin of the
    University of Virginia in Charlottesville. It will help to measure the mass of dark matter
    and its level of influence on visible matter, he says. Though researchershave seen
    smaller versions of such mergers before, says astrophysicist Mike Hudson of the University
    of Waterloo in Canada, with this one investigators will have to "disentangle the wreckage
    and figure out exactly what happened." If it can be done, he says, it should yield
    "important clues to cluster and galaxy formation."



  2. #2
    john030409's Avatar
    john030409 Guest

    Default The Mother of All Pileups [suggests dark matter's hand]

    On Apr 18, 9:55 pm, Sam Wormley <sworml...@mchsi.com> wrote:


    Atoms are unimaginably far apart in gases,
    closer in fluids, and packed together in solids.

    Galaxies do the same thing.

    No, we are not a uniformly-expanding gas.
    There are chunks of fluid or solid
    in that gas.

    Hopefully, we're not a nuclear explosion, but at
    the time scales of galaxies versus atoms, it
    really doesn't matter.

    john
    galaxy model for the atom
    http://users.accesscomm.ca/john/

  3. #3
    hanson's Avatar
    hanson Guest

    Default The Mother of All Pileups [suggests dark matter's hand]


    "john030409" <vegan16@accesscomm.ca> wrote:
    Wormley <sworml...@mchsi.com> cited & wrote:
    The Mother of All Pileups
    http://sciencenow.sciencemag.org/cgi...ull/2009/417/2
    In a faraway corner of the universe, a crash of cosmic
    proportions is under way, cramming more than 1000 galaxies
    into a space normally reserved for a handful. ... [snip]....
    John, the vegan, wrote:
    Atoms are unimaginably far apart in gases,
    closer in fluids, and packed together in solids.
    Galaxies do the same thing.
    No, we are not a uniformly-expanding gas.
    There are chunks of fluid or solid in that gas.
    Hopefully, we're not a nuclear explosion, but at
    the time scales of galaxies versus atoms, it
    really doesn't matter.
    hanson wrote:
    ahahaha... John, calculate your "unimaginably far part"
    distance in a gas under standard conditions: There is
    1 mole of atoms = 6*10^23 atoms crammed into a
    volume of only 22.4 liters, (~ 5 Gallons).
    Now run these numbers... and then give me a definition
    for/or your "far" .... Even in "empty", intergalactic space
    it is conjectured that there are 3-4 atoms per cubic meter,
    which amounts to the atoms being just a foot or so apart...
    ....ahahahahaha... .
    So, John, if you'd made references in your tripe to the
    self similarity of the situation, then you would have
    generated a more palatable view... Do you get it?
    Anyway, thanks for the laughs... ahahahanson

  4. #4
    Damaeus's Avatar
    Damaeus Guest

    Default The Mother of All Pileups [suggests dark matter's hand]

    Reading from news:sci.physics,
    Sam Wormley <swormley1@mchsi.com> posted:


    Was underway a long time ago. The light from it is just now getting here,
    so it's just now observable. Does not mean it's underway now.

    Damaeus

 

 

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