Dark Energy Survey lets scientists glimpse current structure of universe

Dark Energy Camera, one of the most powerful survey instruments of its kind that is able to see light from more than 100,000 galaxies up to 8 billion light years away in each snapshot

Image: College of Science

Scientists with the Dark Energy Survey (DES), including astronomers at Texas A&M University, are celebrating the release of the most accurate measurement to date of the present large-scale structure of the universe.

DES scientists unveiled their most recent findings in a presentation on Aug. 3 at the American Physical Society Division of Particles and Fields meeting at the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory. Their measurements of the amount and “clumpiness,” or distribution, of dark matter in the present-day cosmos were made with a precision that, for the first time, rivals that of inferences from the early universe by the European Space Agency’s orbiting Planck observatory, enabling scientists to understand more about the ways the universe has evolved over 14 billion years.

“This result is beyond exciting,” said Scott Dodelson of Fermilab, one of the lead scientists on this result. “For the first time, we’re able to see the current structure of the universe with the same clarity that we can see its infancy, and we can follow the threads from one to the other, confirming many predictions along the way.”

Most notably, this result supports the theory that 26 percent of the universe is in the form of mysterious dark matter and that space is filled with an also-unseen dark energy, which is causing the accelerating expansion of the universe and makes up 70 percent.

“I thought the discovery of dozens of dark-matter dominated dwarf galaxies orbiting the Milky Way was exciting, but this is really big news,” said Texas A&M astronomer Jennifer Marshall, a DES Builder and member of the survey’s management and science committees. “Ground-based measurements of the universe rarely can rival the precision of space-based projects, and that DES does just that is a testament to the hard work of the scientists and instrument builders across the world who have invested a huge amount of effort in this project.”

The new results released today draw only from data collected during the survey’s first year, which covers one-thirtieth of the sky. The data was captured by the DES’s primary instrument and imaging device, the 570-megapixel Dark Energy Camera (DECam), one of the most powerful in existence for which Texas A&M astronomer Darren DePoy served as the project scientist. Scientists on DES are using the camera to map an eighth of the sky in unprecedented detail during the five-year study, which runs through 2018.

Revered as the most powerful survey instrument of its kind, DECam is able to see light from more than 100,000 galaxies up to 8 billion light years away in each snapshot. A key sub-component of the camera — a spectrophotometric calibration system known as DECal that allows the camera to obtain very high precision brightness measurements of the objects it sees in the sky — was built within Texas A&M’s Charles R. ’62 and Judith G. Munnerlyn Astronomical Laboratory under the direction of DePoy and Marshall.

“We initially got involved with the Dark Energy Survey as the first project our instrumentation lab took on when it was founded in 2008,” Marshall said. “I have been fortunate to become more involved in the scientific productivity and the management of the project during the past few years, and it is incredibly satisfying to see such an impressive result come out of the work that was begun so many years ago.”

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