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  • Cosmic Clumping
    Posted by Frank Morring, Jr. 9:46 PM on Jan 13, 2012

    One possible destination for NASA's planned Orion crew vehicle is the Earth-Moon L2 point, a spot in space where the four-person capsule can essentially hover above the far side of the Moon.

    From there, some planners want astronauts to oversee the robotic construction a huge radio telescope on the lunar surface below.

    The far side is about as radio-quiet a spot as there is, because receivers there are shielded from all the cell phones, TV transmitters and other radio-wave emitters on Earth by the Moon itself.

    Scientists could use that silence to probe hydrogen emissions back when the universe was so new the stars hadn't coalesced and started shining -- the time right after the Big Bang known as the Cosmic Dark Ages.

    It would be fascinating to glimpse the first tentative moves in that primordial cloud toward the highly differentiated universe we know today, as the cosmic ball started rolling toward everything from supermassive black holes to the electric flickerings of the human mind.

    Just as it has conceived of the far-side radio telescope, that mind has produced some amazing instruments for tracking that cosmic clumping. Here is a Hubble Space Telescope image, released at the American Astronomical Society meeting in Austin, Tex., that shows the earliest galaxy cluster ever observed.


    blog post photo

    Light from the five galaxies, imaged in the near-infrared, originated 13.1 billion years ago -- a mere 600 million years after the Big Bang, according to the scientists who found the proto-cluster in a random sky survey.

    Each galaxy is about as bright as the Milky Way, but only one-half to one-10th its size. Astronomers equate brightness with mass, indicating the five galaxies are surrounded by many more less massive galaxies and a "deep well" of the mysterious dark matter that provides the gravity holding the cluster together.

    The discovery lends support to the hierarchical model of galaxy assembly, which posits that small objects merge into larger and larger ones, with the mass to attract even larger objects; stars gather into galaxies, and galaxies into clusters.

    A little closer to the current era, at 7 billion light years from Earth, is this cluster of galaxies that is the largest and hottest found at that distance in time, or earlier.

    blog post photo
    Credit: X-ray; NASA/CSC/Rutgers/J. Hughes et al; Opticalp; ESO/VLT & SOAR/Rutgers/F. Menanteau; IR: NASA/JPL/Rutgers/F. Menanteau

    Dubbed "El Gordo," it is imaged in x-ray (blue) by the Chandra space telescope, optical (red, green, blue) by the European Southern Observatory's Very Large Telescope, and infrared (red, orange) by the Spitzer Space Telescope.

    Close analysis of the data at these wavelengths shows El Gordo is actually two galaxy clusters being smashed together by gravity in a high-speed collision measured at "several million miles per hour," according to NASA.

    Even with multiple wavelengths like those used to generate the El Gordo image, astronomers believe only about 4 percent of the universe can be seen with today's instruments.

    The rest is called dark matter, mainly because science really doesn't know what it is. However, by analyzing the way dark matter distorts light passing through it between distant galaxies and Earth, scientists have been able to map the distribution of dark matter in different directions.

    blog post photo
    Van Waerbeke, Heymans, and CFHTLens collaboration

    When these bright clumps of dark matter are mapped against visible-light images, the role dark matter plays in forming galaxy clusters becomes a little clearer.

    blog post photo
    Van Waerbeke, Heymans, and CFHTLens  collaboration

    "Knowing how dark matter is distributed is the very first step towards understanding its nature and how it fits within our current knowledge of physics," says Prof. Ludovic Van Waerbeke of the University of British Columbia, one of the scientists participating in the Canada-France-Hawaii Telescope Lensing Survey.

    It's another example of the way science is using ever-more-sophisticated instruments to gather ever-more-precise data from the universe around us..

    Tags: os99

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