Texas A&M Astronomers Prove Instrumental in Shedding Light on Dark Energy

Virus. It’s a word that evokes fear and loathing, not to mention immediate and intense connotations, overwhelmingly negative.

As the root cause of a variety of vile maladies ranging from debilitating illness to devastating data loss, viruses are nothing if not notorious for being something to avoid at all costs and, if unleashed either accidentally or deliberately, quickly contained and quarantined.

And yet, astronomers at Texas A&M University can hardly contain their joy at the “VIRUS” they are eagerly anticipating and helping to build, the Visible Integral-Field Replicable Unit Spectrographs (VIRUS), and the light it is expected to shed on one of the Universe’s most puzzling mysteries: dark energy.

This particular VIRUS, otherwise known as the world’s premier spectrograph, will be a key component in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), one of the first international experiments to probe and understand dark energy, the dominant and unexplained force that is causing the Universe to expand at an increasing rate as it ages. Texas A&M is a partner in the $36 million project initiated in 2002 by The University of Texas at Austin that also involves Penn State University as well as several international members.

The first-of-its-kind, $16 million VIRUS instrument, designed by University of Texas astronomer and HETDEX principal investigator Dr. Gary Hill, is being assembled and aligned in Texas A&M’s Charles R. ’62 and Judith G. Munnerlyn Astronomical Laboratory under the direction of Dr. Darren L. DePoy, a world-renowned expert in astronomical instrumentation and holder of the Rachal-Mitchell-Heep Endowed Professorship in Physics in the Texas A&M Department of Physics and Astronomy. DePoy is spearheading the challenging construction of no fewer than 192 individual VIRUS units — each an identical copy of a single spectrograph — as well as the assembly and testing of the overall instrument along with Dr. Jennifer L. Marshall, research scientist in the Department of Physics and Astronomy.

“In astronomy, mostly what we do is build one instrument and put it on the back of a telescope to use, sometimes for many years,” says DePoy, who joined the Texas A&M faculty in 2008 as a member of Texas A&M’s George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy. “This project is different because we are not building one; it is what is, in effect, hundreds of the same thing.”

Once mounted to the sides of the world’s third-largest telescope, the Hobby-Eberly Telescope, located at The University of Texas’s McDonald Observatory in west Texas’s Davis Mountains, the novel array will help produce the largest three-dimensional map of the Universe to date by pinpointing the positions of more than one million far-off galaxies to measure how the Universe expands over time and reveal unprecedented information about dark energy, considered by many to be the most vexing question in science today. The experiment also will measure the geometry of the Universe to very high precision, giving astronomers direct information about the state of the Universe at a time less than one second after the Big Bang.

“We are fortunate at Texas A&M to have both the excellent students and staff as well as the high-quality lab space required to build such precision instrumentation,” DePoy says. “Our team includes undergraduate and graduate students from several science and engineering departments and research scientists and engineers in the instrumentation group. All of us are excited to be part of such a groundbreaking project.”

DePoy notes the VIRUS concept is a first in astronomy, both for its function in the revolutionary HETDEX project and its utilization of industrial replication. He estimates that it will save about 75 percent of the cost it would require to build a single spectrograph big enough to do the job. However, while building one spectrograph is a relatively simple task, Marshall adds that to build nearly 200 is a whole new objective.

“This will be a unique instrument in astronomy that no one has ever done before,” Marshall says.

Hopes are high for VIRUS. Each unit contains a bundle of about 230 optical fibers — nearly 46,000 in all — similar to those that transport telephone calls. Each fiber will be focused on a tiny piece of the sky, and, assuming a distant galaxy lines up with that fiber’s field of view, VIRUS will capture the spectrum of the galaxy.

The odds that less than one percent of the fibers will actually be pointed at a galaxy during any given single observation are daunting but not dissuading, according to DePoy. With the telescope being moved slightly for each of the 140 nights of observing during the course of a three-year span, and with each session lasting 20 minutes, HETDEX will provide images for at least one million galaxies.

Specifically HETDEX is intended to find “Lyman-alpha” galaxies — ancient galaxies that were forming numerous stars roughly 10 billion years ago that glow brightly because of the longer wavelengths brought on by their redshift, a measurable phenomenon that occurs when a galaxy’s light is stretched by the expansion of the Universe. The farther the galaxies are, the greater their redshift and brightness, along with their odds for detection with VIRUS. By comparing the different galactic images from the past and present, scientists will be better able to visualize the Universe’s configuration, which will allow them to measure how dark energy changes as the Universe ages.

“We will be able to look at the pattern of those galaxies on the sky and that will tell us how the Universe is shaped and formed and how it evolved at that time,” DePoy explains. “We know how it is shaped now, but comparing it [to the shape back then] gives us an idea about the parameters at which the Universe changed shape. It will help characterize what dark energy has done over cosmic time.”

HETDEX will measure the waves in the Universe that appeared in the hot gas in the early Universe, about 400,000 years after the Big Bang. These waves of dark matter pull on the Universe’s big inhabitants astronomers can see — for example, galaxies and clusters of galaxies — and have left a faint wave that can still be seen in the spacing between galaxies. This wave is about 400 million light years across at present, but over the next billions of years, it will finally disappear, along with any astronomical clues it potentially could reveal.

While scientists know dark energy exists and that it constitutes roughly 70 percent of all matter and energy in the Universe, the phenomenon has baffled them ever since it was discovered in 1998 by two groups of researchers — one co-founded by Texas A&M astronomer Dr. Nicholas B. Suntzeff — and further cemented in astrophysics history with the 2011 Nobel Prize in Physics. Exactly where dark energy comes from and what it is made of is considered to be one of the most pressing issues in astronomy, Suntzeff says.

“HETDEX is an extremely important project, for our profession and for Texas A&M,” Suntzeff adds. “It funds our instrumentation lab, it challenges the builders, it employs lots of undergraduates and the science is well-suited for our faculty. Add in the collaboration with The University of Texas and, well, I cannot think of a better project.”

Last fall the HETDEX project received an $8 million grant from the National Science Foundation (NSF), nearly half of which is being used to help build VIRUS. Researchers hope to have the instrument built and secured to the telescope by fall 2012, at which time they will begin mapping and obtaining data with the help of a completely upgraded secondary mirror and top end for the Hobby-Eberly Telescope — the fruits of years of collaborative labor by project researchers at McDonald Observatory and The University of Texas’s Center for Electromechanics.

Given that Texas’s two flagship universities are playing major roles in such a revolutionary experiment to understand dark energy, DePoy and Marshall say they have nothing but high hopes for the Lone Star State’s worldwide reputation in astronomical instrumentation and research, not to mention future groundbreaking collaborations to benefit the state and nation.

“To have two of the leading institutions in Texas execute this project and solve one of today’s biggest science problems is a good thing,” DePoy says. “It shows the degree of cooperation we have between these institutions.”

For more information on HETDEX, visit http://hetdex.org/.

To learn more about Texas A&M astronomy, visit http://astronomy.tamu.edu.

# # # # # # # # # #

About HETDEX: The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is a collaboration of The University of Texas at Austin, Texas A&M University, Pennsylvania State University, Leibnitz-Institut füer Astrophysik Potsdam (AIP), Max-Planck-Institut füer Extraterrestrische Physik (MPE), Ludwig Maximilians University, Munich, and Georg-August University, Goettingen. Financial support is provided by the State of Texas, the United States Air Force, the National Science Foundation and the generous contributions of many private foundations and individuals.

About Research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $630 million, which ranks third nationally for universities without a medical school, and underwrites approximately 3,500 sponsored projects. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.

-aTm-

Contact: Shana K, Hutchins, (979) 862-1237 or shutchins@science.tamu.edu, Dr. Darren DePoy, (979) 862-2082 or depoy@physics.tamu.edu or Dr. Jennifer Marshall, (979) 862-2782 or marshall@physics.tamu.edu