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  • richardmitnick 8:39 am on March 12, 2016 Permalink | Reply
    Tags: , , BOSS Great Wall Supercluster, , SDSSIII BOSS   

    From NOVA: “BOSS Supercluster Is So Big It Could Rewrite Cosmological Theory” 

    PBS NOVA

    NOVA

    11 Mar 2016
    Conor Gearin

    BOSS Supercluster Baryon Oscillation Spectroscopic Survey (BOSS)
    BOSS Supercluster

    Astronomers just observed the biggest collection of star stuff that we’ve seen so far.

    An international team of scientists described a huge wall of galaxies in a little-explored part of the cosmos. It’s over a billion light years long, bristling with 830 galaxies. They have dubbed it the BOSS Great Wall, named after the BOSS survey which spotted it.

    At the largest scale, matter in the universe forms long threads and dense clusters—like a net with big knots. Between the threads are voids drained of almost all matter. In 2014, astronomers learned that our Milky Way galaxy is just one of many in the Laniakea supercluster, which is a web of 100,000 galaxies.

    Laniakea supercluster no image credit
    Laniakea supercluster. No image credit

    But superclusters can stick together and form even bigger structures. The BOSS Great Wall is a tight network of four superclusters. The largest two form a stretched-out wall of galaxies that’s about 1.2 billion light years long. This is one of only a few supercluster systems ever found. Only one other system, the Sloan Great Wall, comes close in size, but not quite close enough—BOSS has over twice as many galaxies and is 170% wider than Sloan.

    Sloan Great Wall SDSS
    Sloan Great Wall SDSS

    “It looks like we have a structure that is bigger than anything else: like two Sloan Great Wall scale structures right next to each other,” said Heidi Lietzen of the Institute of Astrophysics at the University of La Laguna in Spain, who was the lead author of the new study. “The question now is: is it too big for our cosmological theories?”

    Scientists are still figuring out what shapes supercluster systems like this one can take, said Elmo Tempel, an astronomer at the Tartu Observatory in Estonia and a co-author on the study. Since they’ve only found a few systems of this scale, astrophysicists aren’t sure whether they always form wall-like structures or if the one’s they’ve seen are special cases. The next step is to run simulations of the shapes that superstructures this massive tend to form, Tempel said.

    Superclusters have their origins in pools of dark matter that formed early in the universe’s history, said Brent Tully of the Institute for Astronomy at the University of Hawaii. Normal matter flows towards the wells of dark matter, giving the universe its web-like structure.

    While Tully agreed that the BOSS Great Wall is indeed the biggest structure in the universe we’ve found so far, he doesn’t think it will change our theories of how the cosmos gets its shape. (There is another contender for largest structure in the universe, but instead of being made of something, it’s made of nothing.)

    “It is not surprising that if we look at a bigger patch of the universe we find something bigger,” Tully said. “But not so much bigger that it disrupts the generally held view of structure formation.”

    What’s more, Tully said that the BOSS Great Wall won’t be the last word on giant superstructures—there’s plenty of universe left to explore. “Look in a new place and you’ll find something new,” Tully said.

    Astronomers already know where to look next. Lietzen explained that the survey data the team used to figure out the large-scale structure of objects only covered a quarter of the night sky. “There could very well be another equally big system of superclusters somewhere in the Southern sky, for example,” Lietzen said.

    *Sloan refers to the Sloan Digital Sky Survey, SDSS, using the SDSS telescope at Apache Point, NM, USA

    **Baryon Oscillation Spectroscopic Survey also ran on the SDSS telescope.

    SDSS Telescope
    SDSS telescope at Apache Pointe, NM, USA

    See the full article here .

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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 2:59 pm on January 8, 2014 Permalink | Reply
    Tags: , , , , , SDSSIII BOSS   

    From Harvard- Smithsonian Center for Astrophysics: “A One-Percent Measure of Galaxies Half the Universe Away” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    Wednesday, January 8, 2014
    For more information, contact:

    David A. Aguilar
    Director of Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    617-495-7462
    daguilar@cfa.harvard.edu

    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    Researchers from the Baryon Oscillation Spectroscopic Survey (BOSS) today announced that they have measured the distance to galaxies more than six billion light years away to an unprecedented accuracy of just one percent. Their measurements place new constraints on the properties of the mysterious “dark energy” thought to permeate empty space, which causes the expansion of the Universe to accelerate.

    uni

    “There are not many things in our daily life that we know to one-percent accuracy,” said David Schlegel, a physicist at Lawrence Berkeley National Laboratory (LBNL) and the principal investigator of BOSS. “I now know the size of the Universe better than I know the size of my house.”

    The new distance measurements were presented today at a meeting of the American Astronomical Society by astronomer Daniel Eisenstein (Harvard-Smithsonian Center for Astrophysics), the director of the Sloan Digital Sky Survey III (SDSS-III), the worldwide collaboration of which BOSS is a part.

    “Determining distance is a fundamental challenge of astronomy,” said Eisenstein. “You see something in the sky – how far away is it? Once you know how far away it is, learning everything else about it is suddenly much easier.”

    Throughout history, astronomers have met this challenge using many different techniques: for example, distances to planets in the solar system can be measured quite accurately using radar, but for more distant objects, astronomers must turn to less-direct methods.

    Regardless of the method, every measurement has some uncertainty, which can be expressed as a percentage of the thing being measured. For example, if you measure the distance from Washington, D.C. to New York (200 miles) to within two miles of the true value, you have measured to an accuracy of one percent.

    Only a few hundred stars and a few star clusters are close enough to have distances measured to one-percent accuracy. Nearly all of these stars are only a few thousand light-years away, and all are still within our own Milky Way galaxy. Reaching out a million times farther away, the new BOSS measurements probe far beyond our Galaxy to map the Universe with unparalleled accuracy.

    With these new, highly accurate distance measurements, BOSS astronomers are making new inroads in the quest to understand dark energy. “We don’t yet understand what dark energy is,” explained Eisenstein, “but we can measure its properties. Then, we compare those values to what we expect them to be, given our current understanding of the Universe. The better our measurements, the more we can learn.”

    Making a one-percent measurement at a distance of six billion light-years requires a completely different technique from measurements in the solar system or the Milky Way. BOSS, the largest of the four projects that make up the Sloan Digital Sky Survey III (SDSS-III), was built to take advantage of this technique: measuring the so-called “baryon acoustic oscillations” (BAOs), subtle periodic ripples in the distribution of galaxies in the cosmos.

    These ripples are imprints of pressure waves that moved through the early Universe, which was so hot and dense that particles of light (photons) moved along with the protons and neutrons (known collectively as “baryons”) that today make up the nuclei of atoms. The original size of these ripples is known, and their size today can be measured by mapping galaxies.

    Making these measurements required mapping the locations of 1.2 million galaxies. BOSS uses a specialized instrument that can make detailed measurements of 1000 galaxies at a time.

    The BOSS measurements are consistent with a form of dark energy that stays constant through the history of the Universe. This “cosmological constant” is one of just six numbers needed to make a model that matches the shape and large-scale structure of the Universe. Schlegel likens this six-number model to a pane of glass, which is pinned in place by bolts that represent different measurements of the history of the Universe.

    “BOSS now has one of the tightest of those bolts, and we just gave it another half-turn,” said Schlegel. “Each time you ratchet up the tension and the glass doesn’t break, that’s a success of the model.”

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.


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  • richardmitnick 12:50 pm on August 8, 2012 Permalink | Reply
    Tags: , , , , , , SDSSIII BOSS   

    From Berkeley Lab: “The First Public Data Release from BOSS, the Baryon Oscillation Spectroscopic Survey” 


    Berkeley Lab

    Led by Berkeley Lab scientists, the Sloan Digital Sky Survey’s BOSS is bigger than all other spectroscopic surveys combined for measuring the universe’s large-scale structure

    sdssiii

    image2

    August 08, 2012
    Paul Preuss

    “The Third Sloan Digital Sky Survey (SDSS-III) has issued Data Release 9 (DR9), the first public release of data from the Baryon Oscillation Spectroscopic Survey (BOSS). In this release BOSS, the largest of SDSS-III’s four surveys, provides spectra for 535,995 newly observed galaxies, 102,100 quasars, and 116,474 stars, plus new information about objects in previous Sloan surveys (SDSS-I and II).

    ‘This is just the first of three data releases from BOSS,’ says David Schlegel of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), an astrophysicist in the Lab’s Physics Division and BOSS’s principal investigator. ‘By the time BOSS is complete, we will have surveyed more of the sky, out to a distance twice as deep, for a volume more than five times greater than SDSS has surveyed before – a larger volume of the universe than all previous spectroscopic surveys combined.’”

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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