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Map reveals the invisible universe of dark matter

The analysis from the Dark Energy Survey comes from observations of 26 million galaxies

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7:00am, August 25, 2017
map of dark matter

MATTER MAP  Scientists with the Dark Energy Survey have created the largest map of the universe’s dark matter. Red areas are relatively crammed with dark matter and normal matter, while blue areas are less dense.

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Scientists have created the largest map of dark matter yet, part of a slew of new measurements that help pin down the universe’s dark contents. Covering about a thirtieth of the sky, the map (above) charts the density of both normal matter — the stuff that’s visible — and dark matter, an unidentified but far more abundant substance that pervades the cosmos.

Matter of both types is gravitationally attracted to other matter. That coupling organizes the universe into more empty regions of space (No. 1 below and blue in the map above) surrounded by dense cosmic neighborhoods (No. 2 below and red in the map above).

empty regions of space

Researchers from the Dark Energy Survey used the Victor Blanco telescope in Chile to survey 26 million galaxies in a section of the southern sky for subtle distortions caused by the gravitational heft of both dark and normal matter. Scientists unveiled the new results August 3 at Fermilab in Batavia, Ill., during a meeting of the American Physical Society.

Dark matter is also accompanied by a stealthy companion, dark energy, an unseen force that is driving the universe to expand at an increasing clip. According to the new inventory, the universe is about 21 percent dark matter and 5 percent ordinary matter. The remainder, 74 percent, is dark energy.

The new measurements differ slightly from previous estimates based on the cosmic microwave background, light that dates back to 380,000 years after the Big Bang (SN: 3/21/15, p. 7). But the figures are consistent when measurement errors are taken into account, the researchers say.

“The fact that it’s really close, we think is pretty remarkable,” says cosmologist Josh Frieman of Fermilab, who directs the Dark Energy Survey. But if the estimates don’t continue to align as the survey collects more data, something might be missing in cosmologists’ theories of the universe.

DARK DENSITY The dark matter and normal matter mapped by the Dark Energy Survey is distributed over a 3-D volume of space, as shown in red in this simulation. Chihway Chang and the DES Collaboration

Citations

T.M.C. Abbott et al. Dark Energy Survey year 1 results: Cosmological constraints from galaxy clustering and weak lensing. arXiv:1708.01530. Posted August 4, 2017.

C. Chang et al. Dark Energy Survey year 1 results: Curved-sky weak lensing mass map. arXiv:1708.01535. Posted August 4, 2017.

D. Gruen. Dark Energy Survey year 1 results. American Physical Society Division of Particles and Fields, Batavia, Illinois, August 3, 2017.

Further Reading

C. Crockett. Using general relativity to magnify the cosmos. Science News. Vol. 188, October 17, 2015, p. 24.

A. Grant. Map pinpoints location of invisible dark matter. Science News. Vol. 187, May 16, 2015, p. 9.

A. Grant. The past according to Planck: Cosmologists got a lot right. Science News. Vol. 187, March 21, 2015, p. 7.

A. Witze. In the dark. Science News. Vol. 179, April 23, 2011, p. 24.

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