Featured Student Stories

Stars shine because they release energy while undergoing nuclear fusion. Eventually, though, a star runs out of material to fuse and no longer releases energy. When that happens to a massive star, it collapses, forming either a black hole or a neutron star. Renee Ludlam has studied both.

Renee has wanted to be an astronomer since she was in middle school but due to her limited choices for undergraduate studies, she figured it just wasn’t going to happen. Nevertheless, the stars aligned for her when Renee started at Wayne State University the same year that the school’s astronomy program did. As an undergraduate, Renee spent a summer at the University of Michigan working with Professor Jon M. Miller, her current graduate advisor, studying black holes.

She has since transitioned from black holes to neutron stars - a move driven by pure curiosity. Renee explains her current research this way: “I look at the most outrageous objects that no one has ever heard of - neutron stars.” A neutron star, located hundreds of lightyears away from Earth and only about the size of a city, is formed upon the collapse of a massive star into a very dense core.

Astronomers are currently using several different complementary methods to learn about neutron stars. Renee looks at X-ray emission features that arise from the material surrounding a neutron star using a method called reflection modeling, a technique developed decades ago for black holes but applied to neutron stars for the first time in 2007. She studies the light that is emitted by a neutron star to figure out its radius and calculates its mass using information about the orbit of the neutron star and its closely related companion star. She can then compare her experimentally determined size to various theoretical models of the relationship between a neutron star’s mass and radius to validate or invalidate them. Ultimately, this process will tell scientists more about how matter behaves under the extreme conditions present in a neutron star.

But it’s not just one star she’s looking at. Renee will likely study tens of stars during her PhD. To do this, collaboration is instrumental. Since X-rays don’t pass into the Earth’s atmosphere, most of the observation for Renee’s project is done in outer space by NASA facilities, including NICER (Neutron star Interior Composition ExploreR), a new instrument on the International Space Station. To move her project forward, Renee participates in weekly telecons with scientists all around the world.

She has also traveled to conferences throughout the continental U.S. and Europe, including giving a talk at NASA. Recently, she’s returned from a trip to the Magellan Telescopes in Chile, where she did some of her own observation of infrared light. On days that don’t involve telecons or travel, you can find Renee at her desk - drinking espresso, performing data analysis, and thinking about the big picture.

Genuine scientific curiosity is the root of what drives not only Renee but her whole field. “There’s so much we don’t know,” she says. Her graduate work is filling in just one small piece of that puzzle.

A gaze at the clear night sky would reveal the light of stars and moon. In between these stars, too faint to see with the naked eye, lie billions of galaxies. How populations of galaxies form and evolve throughout the history of the universe is still a mystery. Bryan Terrazas’s work aims at addressing key issues related to solving it.

Bryan is a sixth-year PhD student working with Professor Eric Bell in the Astronomy department. He studies how black holes can affect star formation in galaxies and how this can change the way these galaxies grow. A typical day for Bryan involves coding at his desk, chatting with Prof. Bell about science, or attending meetings and colloquia to get a sense of the research going on inside and outside of the department. Specifically, Bryan works on analyzing state-of-the-art simulations run on supercomputers that attempt to model the physics most important for galaxy evolution. Bryan and collaborators put these models to the test by identifying how these simulated universes differ from the real universe, with the aim of understanding the physical mechanisms that drive these differences.

Most galaxies have a supermassive black hole at their center, but the relationship between the black hole and its host galaxy has been difficult to understand. Bryan’s work seeks to address how the relatively small-scale physics governing black holes can affect large-scale galactic star formation. An important discovery in his research shows that galaxies with bigger black holes are forming fewer new stars. This suggests that central supermassive black holes have a key role in determining the evolution of galaxies in the universe. Galaxies are sensitive to all the physics from the nuclear fusion of subatomic particles in the cores of stars to the large scale gravitational structures in which they live. The complex interplay between all of these processes at different scales throughout the age of the universe produces billions of beautiful and unique galaxies. He explains, “Galaxies are like people because each one is different from one another. Each galaxy has their own story to tell, and as astronomers we’re interested in hearing that story.”

Collaboration forms the foundation of Bryan’s work. He notes: “ [Astronomy] advances through the exchange of ideas at all levels, from professors to undergraduates. This reflects the necessity for creativity and thinking outside the box, which can be best achieved by talking with others.” In a recent trip to the Max Planck Institute for Astrophysics in Munich, Germany, he worked collectively with other scientists to discuss results from the IllustrisTNG simulation suite, compare them with the real universe, and understand the physics they can elicit from these analyses. While astronomers can model tens of thousands of galaxies in one simulation, it remains difficult to fully capture all the physics of galaxy formation in a single model.

Bryan has also learned several important lessons about being in graduate school. He believes finding how to balance life by not only doing research but also by living holistically is crucial to the journey. After initially feeling uprooted during his first year, he became more grounded as he pursued activities beyond his PhD studies such as playing the clarinet, honing his cooking skills, learning how to paint, and regularly working out. These endeavors were critical to his evolution as a scholar, student, and human: “my astronomy got better, my research progressed more, and I was able to focus.”

By tracing the histories of how galaxies grew to be, he is able to distill the complexities of galaxy formation into a historical narrative to make them digestible to broader audiences. As astronomers learn more about the universe, Bryan believes it is also critical for them to share this knowledge in accessible ways to a general audience. This locates the greatest impact of Bryan’s work: “to think outside the box and artistically about my science and what’s going on in the universe”. He believes this thinking necessarily involves expanding science to include different marginalized identities and leveraging the platform of science to implement meaningful diversity, equity, and inclusion.