MIT physicist maps black holes through X-ray echoes, unlocking galaxy formation secrets

Erin Kara sits in her office at MIT, thinking about the impossible: how to see what happens billions of light-years away, in the violent neighborhoods of black holes. She is an associate professor of physics, and her work hinges on a simple but elegant idea—that X-rays bouncing off the material swirling around a black hole can tell us something true about the universe's most extreme places.

Kara grew up in Bethlehem, Pennsylvania, the youngest of four children in a household where medicine was the expected path. Her mother was a nurse, her father a doctor. She enrolled at Barnard College as a premed student, dutifully taking the required introductory physics course. But something shifted in that classroom. Physics, she realized, explained the world at its most fundamental level—from the quantum realm to the cosmic scale. She kept asking questions. Her professor, astronomer Reshmi Mukherjee, noticed and invited her to join a research team working with newly arriving data from NASA's Fermi Gamma-Ray Space Telescope, which launched in June 2008. That summer internship became the hinge of her life. Kara was assigned to characterize two unidentified gamma-ray signals—bright spots in the sky that could have originated either nearby in the Milky Way or from distant quasars, the extraordinarily active cores of faraway galaxies. She analyzed the data and confirmed both sources were indeed quasars. It was a small discovery, but it felt transformative. "There are so many unanswered questions," she would later reflect, "and even early on in your career, you can make an impact."

She switched her major to physics. The transition was not seamless. At Barnard's all-women introductory courses, she felt capable and supported. But upper-level classes were held at Columbia, where she was one of many students in a larger, coeducational cohort. Suddenly her confidence wavered. The men around her seemed more assured, more fluent in the material. Yet she performed well. That contrast—between environments, between how she felt about herself in each—taught her something crucial: belonging is not fixed. It shifts with context. She did belong.

After graduating with a degree in physics and a minor in art history, Kara pursued a master's degree at Cambridge University's Institute of Astronomy on scholarship. She stayed to complete a PhD, working under Andy Fabian on a nascent field: black hole X-ray reverberation. In 2009, Fabian's team was sifting through archival data from an X-ray telescope when they noticed something curious—time delays in signals emanating from near a black hole. They interpreted these as echoes: X-rays generated in the black hole's corona, a crown of superheated radiation immediately surrounding the event horizon, bouncing off the accretion disk—the swirling disk of gas and dust that orbits the black hole. It was the first evidence of such echoes, and it resolved a longstanding debate about where the radiation originated. Kara realized the archive contained far more data that had never been analyzed this way. Her entire PhD became an exploration of these reverberations, a discovery-driven deep dive into cosmic echoes.

After earning her doctorate, Kara moved to the University of Maryland and NASA's Goddard Space Flight Center for postdoctoral work. She was assigned to a Japanese satellite called Hitomi, designed to detect distant X-rays and map the universe's large-scale structure. Forty days after launch, the satellite spun out of control and disintegrated in orbit. But before it failed, it sent back one pristine observation—a spectrum unlike anything scientists had seen before. The data vindicated the satellite's detector, a sensitive microcalorimeter developed at NASA. That technology now forms the backbone of XRISM, Hitomi's successor, which has been successfully gathering data since 2023. Kara now leads a science group analyzing X-ray signals from supermassive black holes as part of the XRISM mission. But in that moment of loss, she had to adapt. She joined a new team at Goddard preparing for the launch of NICER—the Neutron Star Interior Composition Explorer—an instrument built by MIT researchers and attached to the International Space Station in 2017. This telescope measures the precise timing of incoming X-rays from distant sources. The group was hunting for tidal disruption events, moments when a black hole's gravity tears apart a nearby star. This work became foundational to her research agenda.

In 2019, Kara accepted a junior faculty position in MIT's Department of Physics. The decision felt inevitable. X-ray astronomy had deep roots at MIT, pioneered by figures like Bruno Rossi, Hale Bradt, George Clark, and Claude Canizares. "It was always a place that felt like a hub," she says. Today, Kara and her students analyze data from satellites and telescopes including XRISM and NICER, working to understand how black holes grow, evolve, and shape the galaxies around them. She continues refining X-ray reverberation mapping, a technique that has allowed scientists to map the extreme regions immediately surrounding black holes with unprecedented precision. Her group also studies other violent phenomena: tidal disruption events, quasiperiodic eruptions, and galactic black hole outbursts. Looking forward, she plans to incorporate data from ULTRASAT, a satellite that will continuously scan the sky for hot ultraviolet sources, and LISA, a space-based gravitational wave detector that will observe pairs of mismatched black holes colliding across the cosmos. In 2022, Kara collaborated with MIT educators and music anthropologists to convert a black hole's X-ray echoes into audible sound. As a musician—she sings and plays violin—she was curious what cosmic violence might sound like. The result was otherworldly, a translation of extreme physics into human sensation.

What drives her, ultimately, is the paradox at the heart of her work. Black holes are extreme, almost incomprehensible places where physics breaks down. Yet they are also foundational to existence itself. The distribution of stars, gas, and dust in every galaxy—including our own—is shaped in part by the supermassive black hole at its center. Our sun is one of those stars. The black hole and the galaxy are intertwined, and untangling that relationship is the work of her life.