Pitt Astronomers Exploring Dark Energy

PITTSBURGH—Two hundred physicists and astronomers, including Jeffrey Newman and Andrew Zentner of the University of Pittsburgh, are one step closer to a deeper understanding of “dark energy,” the unknown phenomenon causing the expansion of the Universe to accelerate rather than slow down because of gravity.

Astronomers at the University of Pittsburgh have been working on developing a new project known as DESI, the Dark Energy Spectroscopic Instrument. Today, the U.S. Department of Energy approved the project’s scientific scope, schedule, and funding profile, enabling work on DESI to begin.

Newman, an associate professor in Pitt’s Department of Physics and Astronomy within the Kenneth P. Dietrich School of Arts and Sciences, and colleagues have developed new techniques for selecting which galaxies DESI should observe in order to map out the underlying structure of dark matter most efficiently. This work focuses on finding a class of objects known as “luminous red galaxies,” which are among the oldest and most massive galaxies in the universe. These galaxies are found only in the most massive concentrations of matter, serving as visible signposts of where dark matter can be found. Meanwhile, Zentner, also an associate professor in the department, is working on improving the theoretical underpinnings and developing new methods for the measurements DESI will make.

“Pitt has been a leader in the development of large projects to explore the distant universe and unravel the mysteries of dark matter and dark energy,” explained Newman. “DESI will enable a revolutionary step forward in our ability to solve some of the greatest problems in physics today.”

Fundamentally, DESI will help reveal how dark energy and gravity have competed over time to shape the universe. DESI will make a three-dimensional map of more than 30 million galaxies and quasars, using them to trace the underlying distribution of dark matter and to chart the largest structures in the universe. With DESI’s precision measurements of how the pattern of matter clustering has expanded over time, scientists can probe the nature of dark energy in detail. Simultaneously, DESI will determine how efficiently gravity attracts galaxies into higher-density regions of the universe, which provides a strong test of whether Einstein’s general theory of relativity is accurate on cosmic scales.

These measurements will be made using a new, state-of-the-art instrument mounted on the 4-meter Nicholas U. Mayall Telescope at Kitt Peak National Observatory near Tucson, Ariz.  DESI will use robotically-positioned fiber optics to gather light from nearly 5,000 objects at a time, allowing it to rapidly map out the universe as it appeared up to 12 billion years in the past (more than 85 percent of the way back to the Big Bang).

Key to DESI’s present and future success is its robust scientific collaboration, incorporating 31 universities and 18 governmental and private institutions, in both the United States and other countries. DOE and the National Science Foundation will shortly begin joint support for Mayall Telescope operations, preparatory work, and installation of the DESI instrument, paving the way for DESI to begin taking data by 2019.

Work on the DESI project at the University of Pittsburgh is supported by the U.S. Department of Energy, Office of Science, and Office of High Energy Physics under award number DE-SC0007914.

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