Uncovering secrets about the universe involves more than what meets the eye. When drawing conclusions about the structure, origin, and temperature of faraway observations, scientists need more than light. They need color.

“By seeing which colors are missing from a star, I can tell how much iron, how much magnesium, how much silicon, how much neodymium is there,” said Evan Kirby, an associate professor in the Department of Physics and Astronomy. “If I measure the compositions of a bunch of stars, then I can learn about the evolution of elements in the universe.”

Kirby is a galactic archeologist, using the elements present in stars today to uncover the history of stars that exploded in the past. That discovery process depends on a technique that captures a detailed range of color possibilities, known as a spectrum. For decades, leading astronomers from around the world have turned to a powerful spectrograph called DEIMOS, which splits starlight into thousands of component colors.

Based at the W.M. Keck Observatory in Mauna Kea, Hawaii, DEIMOS has enabled around 85 percent of Kirby’s research throughout his career. He calls it “an 8,000-color box of Crayola crayons.” But after being in use for over two decades, DEIMOS needed upgrades to its detector system, which determines the range of light it can interpret and the efficiency with which it does so.

“DEIMOS will now be particularly more sensitive in the bluer regions of the spectrum,” Kirby said. “The bluer regions of the spectrum are actually very rich in these absorption lines of … heavy elements at the bottom part of the periodic table. Those elements are really important for nuclear energy.”

Blue detection is at the center of Kirby’s research inquiries, which focus on stars in nearby galaxies — or as Kirby calls them, “the Milky Way’s groupies.” But the upgrade will also improve cases that look at faraway galaxies, where light shifts toward the red end of the spectrum.

This range of applications emerged from ongoing conversations among colleagues who use DEIMOS for different purposes, and had different visions for its future. Some of these exchanges and recommendations started in 2011, when Kirby was still a postdoctoral fellow at the California Institute of Technology (Caltech). He later became a faculty member and eventually the principal investigator to the DEIMOS upgrade, which the California Association for Research in Astronomy funded.

“By getting together a sort of coalition of people who are interested in various ways the upgrade can make their science better, the conversation started,” Kirby said.

When Kirby joined Notre Dame as a faculty member in 2021, he encountered world-class resources for building a new piece of equipment. Experts at the Engineering & Design Core Facility (EDCF) refined the design and assembled the instrument on campus. The EDCF helps develop cutting-edge technologies for researchers — including astronomy equipment, software development, electrical devices, and more.

“One of the things that we had to test was how DEIMOS responds to different rotation angles,” Kirby said. “So the creative engineers at EDCF bought an engine stand — like, for a car — mounted DEIMOS on it, and spun it around slowly. Working with this team of people here at Notre Dame, you just plug right into it. I didn't have to hire anyone new.”

To ensure a clean environment, the EDCF’s assembly process took place in Notre Dame’s Nanofabrication Facility, a state-of-the-art cleanroom in the Stinson-Remick Hall of Engineering.

“Any moisture that's in the system, any oil that's in the system can come out … and these optical components and very expensive camera arrays that are in there can get things accumulated on them,” EDCF Lead Engineer James Smous said. “That would be very bad for the measurement resolution.”

Throughout the two-year design process, the engineers kept a few key specifications in mind. They had to ensure that DEIMOS — despite being the size of a passenger van — could move smoothly while tracking the rotation of the night sky. This involved positioning an element known as a cryostat: a chamber containing liquid nitrogen, which maintains a low temperature to preserve the sensitivity in DEIMOS’s state-of-the-art light detectors. An innovative hexapod design can move the 180-pound cryostat with incredible precision — taking steps as small as 1/1000th the width of a human hair.

“There were a lot of questions that we wanted to address in the design,” Smous said. “How much hold time do you get? What if the power goes out and you can't get to [the cryostat] to refill it with liquid nitrogen?”

Alongside Smous, Mechanical & Aerospace Engineer David Cavalieri and Mechanical Engineer Josh Holewczynski carried out Phase I of the build before shipping the cryostat assembly to Caltech for completion. To ensure the vessel stayed protected in transit, the University’s carpentry shop built a custom shipping crate — the same one that will protect the device on its ultimate journey to Mauna Kea.

While Phase I of the upgrade involved mechanical engineering and assembly, Phase II will consist of additional electronic work, including detector installation.

“I'm still in touch with Caltech weekly, as they're integrating their parts,” Holewczynski said. “The three of us specialized in different areas of the instrument, so as assembly and testing continues at Caltech, we're sometimes called on to help explain how certain things work or to advise on potential changes. This constant communication is so important to making sure Caltech and Notre Dame deliver the best possible upgrades to the observatory.”

Holewczynski and Cavalieri spent months manipulating the instrument in the Clean Room, so they will also play a vital role in the hands-on installation process, which is scheduled for this fall in Mauna Kea. Caltech and Notre Dame collaborators will work to move the device into place at the Keck Observatory — a process that could take two weeks or more.

“It's always a moment of truth when what you've been looking at on your screen in 3D is now real,” Cavalieri said. “It’s an exciting, good stress.”

After installation, scientists around the world will continue turning to DEIMOS for the study of galaxies near and far, Kirby anticipates. Beyond its most obvious function — measuring stellar compositions — Kirby sees potential for DEIMOS to elucidate other contemporary research questions.

“As a byproduct of the spectrum, we get the radial velocities of the stars, so we know the motions of the stars,” Kirby said. “The speed at which stars move is sensitive to galaxies’ mass, so just for free, I get the dark matter content and can tell you something about dark matter in these galaxies.”

While helping astronomers share stories about the universe’s formation and origins, DEIMOS carries an earthside history of its own — one that now includes Notre Dame.

Contact

Martha Reilly / Web and Social Media Program Manager

Notre Dame Research / University of Notre Dame

mreill14@nd.edu

research.nd.edu / https://www.linkedin.com/company/undresearch/

About the Engineering and Design Core Facility

The Engineering and Design Core Facility (EDCF) provides design and related laboratory services to support experimental research endeavors in order to develop cutting-edge technologies. Supporting electrical, mechanical, optical, software, and systems engineering, the EDCF welcomes users from all departments at the University of Notre Dame, as well as other academic and industrial institutions. Learn more about the EDCF’s recent work or reach out to start a new research project.

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The University of Notre Dame is a private research and teaching university inspired by its Catholic mission. Located in South Bend, Indiana, its researchers are advancing human understanding through research, scholarship, education, and creative endeavor in order to be a repository for knowledge and a powerful means for doing good in the world. For more information, please see research.nd.edu or NDR's LinkedIn.