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    Measuring the Milky Way: One massive problem, One new solution

    June 1, 2016, Categories  Astronomy/Space

    The Milky Way. Credit: NASA

    The Milky Way. Credit: NASA

    It is a galactic challenge, to be sure, but Gwendolyn Eadie is getting closer to an accurate answer to a question that has defined her early career in astrophysics: what is the mass of the Milky Way? The short answer, so far, is 7 X 1011 solar masses. In terms that are easier to comprehend, that’s about the mass of our Sun, multiplied by 700 billion. The Sun, for the record, has a mass of 2 nonillion (that’s 2 followed by 30 zeroes) kilograms, or 330,000 times the mass of Earth.

    “And our galaxy isn’t even the biggest galaxy,” Eadie says.
    Measuring the mass of our home galaxy, or any galaxy, is particularly difficult. A galaxy includes not only stars, planets, moons, gases, dust and other objects and material, but also a big helping of dark matter.

    Eadie, a PhD c...

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    Supermassive Black Holes do not form from Stellar Black Holes

    April 6, 2016, Categories  Uncategorized

    Slices of collapsing gas within dark matter halos on three different spacial scales: from 10,0000 to 10 light years across. The colors represent the gas density, from low density (blue color) to much larger density (red color). The gas on the smallest spatial scales is going to form a supermassive black hole. Credit: Isaac Shlosman, University of Kentucky

    Slices of collapsing gas within dark matter halos on three different spacial scales: from 10,0000 to 10 light years across. The colors represent the gas density, from low density (blue color) to much larger density (red color). The gas on the smallest spatial scales is going to form a supermassive black hole. Credit: Isaac Shlosman, University of Kentucky

    Often containing more than a billion times the mass than our Sun, supermassive black holes have perplexed humans for decades. But new research by astrophysicist Isaac Shlosman and collaborators will help to understand the physical processes, providing details of how supermassive black holes formed 13 billion years ago...

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    What Dark Matter Might Be: Researchers present a new model and how to test it

    March 14, 2016, Categories  Astronomy/Space

    The value of the Hubble rate at the start of reheating that gives the correct relic abundance, as a function of the mass of the PIDM. The blue curve is for γ=1 , the orange curve is for γ=0.1 , and the green curve is for γ=0.01 . The red region is excluded from the current bound on the tensor-to-scalar ratio, and the purple dashed line is the projected sensitivity for next generation CMB experiments, from Ref. [24]. The dotted lines show the modification when taking also gravitational production into account [12, 13, 14]. The dashed-dotted line marks mX=Hi , and for a scalar PIDM the left-hand side of this line is excluded unless corrections to the PIDM potential are important during inflation. All values are given in units of Mp .

    The value of the Hubble rate at the start of reheating that gives the correct relic abundance, as a function of the mass of the PIDM. The blue curve is for γ=1 , the orange curve is for γ=0.1 , and the green curve is for γ=0.01 . The red region is excluded from the current bound on the tensor-to-scalar ratio, and the purple dashed line is the projected sensitivity for next generation CMB experiments, from Ref. [24]. The dotted lines show the modification when taking also gravitational production into account [12, 13, 14]. The dashed-dotted line marks mX=Hi , and for a scalar PIDM the left-hand side of this line is excluded unless corrections to the PIDM potential are important during inflation. All values are given in units of Mp .

    Though no one has ever seen it indisputable physical cal...

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    Dark Matter Satellites Trigger Massive Birth of Stars

    March 10, 2016, Categories  Astronomy/Space

    This is a dwarf galaxy with a starburst. Credit: UC Riverside

    This is a dwarf galaxy with a starburst. Credit: UC Riverside

    Astronomers use computer simulations based on theoretical models to explain massive star formation observed in dwarf galaxies. One of the main predictions of the current model of the creation of structures in the universe, known at the Lambda Cold Dark Mattermodel, is that galaxies are embedded in very extended and massive halos of dark matter surrounded by many thousands of smaller sub-halos also made from dark matter.

    Around large galaxies, eg Milky Way, these dark matter sub-halos are large enough to host enough gas and dust to form small galaxies on their own, and some of these galactic companions, known as satellite galaxies, can be observed...

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