• Breaking News

    Saturday, August 05, 2017

    Cosmic Map Reveals a Not-So-Lumpy Universe

    Cosmologists have produced the biggest map yet of the Universe’s structure and they find it less lumpy than previous surveys have suggested.

    The new results, part of the ongoing Dark Energy Survey (DES), charted the distribution of matter in part by measuring the way that mass bends light, an effect known as gravitational lensing. The Universe was extremely smooth, with matter evenly distributed in its infancy nearly 14 billion years ago, but mass has been clumping together ever since into galaxies, gas clouds and other structures. Data released by the DES team on August 3 suggest that the clumping has happened more slowly than indicated by earlier estimates, which were based on baby pictures of the Universe made by measuring the cosmic microwave background, the afterglow of the Big Bang.
    The difference in the results produced by the two techniques is still within the margins of error in both sets of measurements, say the survey leaders. A smaller gravitational-lensing survey, the Kilo Degree Survey (KiDS) also found a similar discrepancy last year.
    Either way, the results show that DES is now reaching levels of precision that make it competitive with microwave-background surveys—including those by the European Space Agency's Planck satellite — says survey leader Joshua Frieman, a cosmologist at the Fermi National Accelerator Laboratory in Batavia, Illinois. “We believe that, with these results, we’re no longer the poor cousin” to other efforts, he says. “We now have result that have comparable power to constrain cosmology.”
    DES, a collaboration of more than 400 researchers, employs the still-young technique of weak gravitational lensing using the 4-metre Blanco telescope, part of the Cerro Tololo Inter-American Observatory in Chile. According to Albert Einstein’s general theory of relativity, mass warps space, so a large amount of matter in the foreground of a galaxy can bend its light in a way that makes it look slightly squashed. This is true whether the foreground mass is made of invisible dark matter or ordinary matter. Galaxies can often appear oblong for other reasons, including their actual shapes and orientation; but if many galaxies in a certain region of the sky appear on average to be skewed along the same direction, gravitational lensing is the likely culprit.
    Read more here : https://www.scientificamerican.com/article/cosmic-map-reveals-a-not-so-lumpy-universe/

    No comments:

    Post a Comment