Stellar minds: CWRU women astronomers map universe’s mysteries

Aug. 1 is Women Astronomers Day, highlighting the historical achievements of women in astronomy. The designation honors the birthdate, in 1818, of Maria Mitchell, the first American woman astronomer and professor of astronomy.

At Case Western Reserve University, astrophysicists Idit Zehavi and Johanna Nagy work in theoretical and experimental cosmology, respectively; fields that straddle astronomy and physics.

Theorists develop and interpret models of the universe, while experimentalists design and build instruments to test the models. Both are members of the Center for Education and Research in Cosmology and Astrophysics at CWRU.

Idit Zehavi

“When I was a kid, I wanted to be an astronaut,” said Zehavi, professor of physics.

In high school, Zehavi took a course in astronomy at the Weizmann Institute of Science in Rehovot, Israel, where she grew up, that captured her imagination. She majored in physics and math as an undergraduate at the Hebrew University of Jerusalem.

“But astronomy was always in the back of my mind,” she said.

Zehavi continued there in physics as a graduate student and took a class with a professor who was interested in the large-scale structure of the universe. She worked with him as her adviser and wound up making a career out of it.

Her research is at the interface of theory and observations, doing statistical analyses of data and numerical simulations of how structures form in the universe. She uses data collected from large galaxy surveys, like the Sloan Digital Sky Survey (SDSS), which has mapped a million galaxies to a depth of four billion light years.

The bright pinpoints of light—each an individual galaxy—in an image from the survey resemble a spider web on a cosmological scale. The questions she tries to answer are how these large-scale structures formed and what can be inferred about the relation of galaxies to the invisible matter of the universe—called “dark matter”—that we can’t see.

“We don’t know what dark matter is,” she said, “but we do know it makes up most of the mass of the universe.”

Before joining the CWRU faculty in 2006, Zehavi held research positions at the Fermi National Accelerator Laboratory near Chicago, the University of Chicago and the University of Arizona. Her published research is among the most cited in her field.

The collegiality of the physics department and the quality of the students at Case Western Reserve continues to impress Zehavi. She coordinates the physics senior project program and said she is inspired by the students’ research and the way they communicate about it.

In addition to the phenomenal students and colleagues at CWRU, what she most enjoys is working with her collaborators around the world, Zehavi said. “I love exploring and solving the mind-boggling mysteries of the universe.”

Johanna Nagy

Nagy, the Warren E. Rupp Assistant Professor of Physics, first came to Case Western Reserve as a graduate student in physics before returning to the university as an assistant professor in 2023.

As experimentalists, she and her collaborators travel regularly to Antarctica to deploy instruments, both at McMurdo Station, on the coast, and the South Pole.

“We develop the technology, build the instruments and test them, deploy them—and then look at the data and get the scientific results,” she said. “That’s unique, because often people focus (only) on observations or on building instruments, but I work in a subfield of astronomy that has historically been very end-to-end, which I love.”

More specifically, Nagy is searching for variations in what’s called the cosmic microwave background (CMB)—light from when the universe first formed.

“We are looking for a signal from when the universe was much less than one second old,” Nagy said, “and trying to see if some of the microwave photons that reach us are polarized or flipped—like looking in a mirror.” Seeing expected patterns in polarization would tell whether or not the universe went through a period of rapid expansion—like blowing up a balloon—called “inflation.”

Many theories suggest this polarization originates from gravitational waves rippling through the early universe. These provided the initial density variations that later grew into galaxies and large-scale structures like the cosmic web Zehavi studies.

To observe the microwave photons, Nagy builds telescopes that can be carried on balloons 120,000 feet high. Balloon telescopes are cheaper and faster to build than space instruments and can see higher frequencies than ground-based telescopes. The balloons are flown from Antarctica to take advantage of 24-hour daylight in December and January, which allows them to fly for three to four weeks.

Nagy began building instruments to study the CMB as an undergraduate at Stanford University and was drawn to Case Western Reserve as a graduate student to work with John Ruhl, Connecticut Professor in Physics, a CMB specialist building instruments for the South Pole Telescope as well as an Antarctic balloon telescope.

“As a faculty member, I appreciate having John as a collaborator, and strong theoretical cosmologists, like Idit, as well as Glenn Starkman (Distinguished University Professor and vice-chair of physics) and Kurt Hinterbichler (associate professor of physics),” said Nagy, a Cotrell Scholar who was recognized by NASA as a Nancy Grace Roman Technology Fellow in Astrophysics in 2024.

 “When you’re chatting with theorists, they come up with something that would be cool to measure, and you start thinking about how you can go measure it,” she said. “It’s a reminder of why we’re doing the science in the first place.”

Evalyn Gates and Heather Morrison

Two other women faculty astronomy researchers are affiliated with CWRU:

Theoretical cosmologist Evalyn Gates is an adjunct faculty member in physics. She’s widely recognized for her research on gravitational lensing—the bending of light from the gravity of dark matter—and understanding the large-scale structure of the universe. A prominent science communicator, she is perhaps best known as director of the Cleveland Museum of Natural History from 2010-18 and author of Einstein’s Telescope: The Hunt for Dark Matter and Dark Energy in the Universe.

And astronomer Heather Morrison, emeritus professor of astronomy, is internationally recognized for her research on understanding the structure and evolution of galaxies, particularly the Milky Way galaxy.

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