Dark Energy Survey maps 26 million galaxies

The Universe may be a little less lumpy than previously thought, according to the newest, biggest map to date of its structure.
By Ed Mason | Aug 22, 2017
The Universe may be a little less lumpy than previously thought, according to the newest, biggest map to date of its structure.

The on-going Dark Energy Survey (DES), which is a collaboration of more than 400 researchers, used the technique of weak gravitational lensing to map the shapes of 26 million galaxies in the southern sky, according to a report in the journal Nature. The scientists then measured the density of matter by calculating the amount of gravitational lensing in each part of the sky.

Fourteen billion years ago matter was evenly distributed throughout the Universe. Since then, mass has been clumping into such cosmic structures as galaxies and gas clouds.

Albert Einstein's general theory of relativity says that because mass warps space, the large amount of matter ordinary matter or invisible dark matter in a galaxy's foreground will bend light in a predictable way.

The researchers found a slightly smaller amount of dark matter than earlier microwave-background surveys, such as those conducted by the European Space Agency's Planck satellite. They also measured a somewhat lower concentration of clumping than the standard model of cosmology predicts.

While the discrepancy between the standard modeling and the DES calculations is not large, if confirmed it could indicate that mass has been clumping more slowly than expected, bringing new physics into play.

The DES study was presented Aug. 3 at a meeting of the American Physical Society at Fermilab. While the results have not yet been peer-reviewed, the authors posted 10 papers online.

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