Missouri S&T joins dark energy experiment to solve accelerating cosmos mystery

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On September 26, 2019

The image represents the evolution of the universe over 13.77 billion years with an expansion history of two accelerated regimes: an inflation at the very beginning that produced a burst of exponential growth, and a more recent regime where the dark energy effects dominate the expansion. Dr. Saito’s group at Missouri S&T is tackling the mystery of dark energy through its international collaboration with HETDEX. Image credit: NASA/WMAP Science Team.

Missouri S&T has joined the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) as one of 11 international institutions that are collaborating to define the force causing the accelerated expansion of the universe.

“The cosmic acceleration is one of the biggest mysteries in our fundamental physics,” says Dr. Shun Saito, cosmologist, assistant professor of physics and leader of Missouri S&T’s HETDEX research group.

“To explain this phenomenon we believe began 5 billion years ago, we must introduce an unknown energy component with negative pressure into the universe. That component is what we now call ‘dark energy,’” Saito says.

Serendipity marks the quest

Two independent scientific teams unexpectedly discovered cosmic acceleration in 1998. They had initially set out to prove the deceleration of the universe based on a common belief that the universe was dominated by matter, and that its expansion would be slowed down by the pull of gravity. Their discovery that the expansion was not slowing down, but actually accelerating, led to the 2011 Nobel Prize in Physics for three members of those teams.

Saito says the best prevailing model to define dark energy is the cosmological constant — Einstein’s concept of the energy density or vacuum energy of space he introduced in 1917 when he wanted to stop the universe from collapsing.

“HETDEX is stepping into unexplored territory of the universe,” says Saito. “The discovery potential of the experiment is huge — we may be able to find that dark energy isn’t Einstein’s cosmological constant, and this would require a new understanding of fundamental physics.”

To pursue this quest, Missouri S&T recently joined HETDEX through a memorandum of understanding between the University of Missouri Board of Curators on the recommendation of S&T’s physics department, and the University of Texas at Austin on behalf of its McDonald Observatory, located in the Davis Mountains of West Texas.

Galaxy mapping at its best

The McDonald Observatory contains the Hobby-Eberly Telescope (HET), one of the world’s largest optical telescopes. It has a primary mirror made up of 91 hexagonal segments, and was recently upgraded to a usable aperture of 10 meters with a new wide-field instrument suite, specifically for the HETDEX project.  

“The immense light-gathering power of this telescope allows us to map out one million distant galaxies that are 9 to 11 billion light-years away,” Saito says. Saito will contribute to HETDEX by analyzing the gigantic three-dimensional galaxy maps produced from a set of 78 spectrographs mounted on HET.

“Intensity mapping is a novel technique for observing the large-scale structure of the universe — it’s our future,” says Saito. “It gives us a more efficient and powerful way to extract cosmological information from the data. Even though the technique is mainly used by radio astronomers, we hope to pioneer it in the optical field with HETDEX.”

HETDEX observations began in December 2017, and Saito expects the project to continue for about three years.

S&T expands astrophysics program

Dr. Shun Saito

Over the last year, Missouri S&T has focused on further advancing its astrophysics program.

Saito joined S&T in January from the Max-Planck-Institute for Astrophysics in Germany, where as a postdoctoral researcher, he contributed his cosmological mapping expertise to HETDEX and other spectroscopic, or light-measuring, galaxy surveys. He also contributed to the Baryon Oscillation Spectroscopic Survey in the Sloan Digital Sky Survey-III where space-time measurements were used to investigate dark energy.

Dr. Siddhartha Gurung-Lopez from Centro de Estudios de Física del Cosmos de Aragón in Spain recently joined S&T’s HETDEX research group to simulate realistic, computer-generated galaxy populations to compare to the HETDEX observations.

“Missouri S&T’s astrophysics program is off to an excellent start,” says Dr. Thomas Vojta, chair of the physics department and Curators’ Distinguished Professor of physics. “With our participation in HETDEX and in the LIGO (Laser Interferometer Gravitational-wave Observatory) Scientific Collaboration, we now have cutting-edge research groups in gravitational wave physics and in cosmology. S&T is keeping its eyes wide open to the sky.”

HETDEX is a collaboration of The University of Texas at Austin, Pennsylvania State University, Texas A&M University, Ludwig Maximilian University of Munich, Leibniz Institute for Astrophyics Potsdam (AIP), Max Planck Institute for Extraterrestrial Physics, Max Planck Institute for Astrophysics, Institute for Astrophysics in Göttingen, The University of Oxford, The University of Tokyo and Missouri University of Science and Technology. Financial support is provided by the State of Texas, the United States Air Force, the National Science Foundation, partner institutions and the generous contributions of many private foundations and individuals.

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On September 26, 2019.

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