From Variable Stars to Dark Matter – The Expanding Legacy of Henrietta Leavitt
Henrietta Swan Leavitt’s early twentieth-century discovery of a relationship between the brightness of certain stars named "Cepheid variables” and the duration of their brightness cycles transformed astronomy. By showing that a star’s intrinsic luminosity could be inferred from its variation period, Leavitt provided the first reliable method for measuring astronomical distances beyond our galaxy and established the foundation for what became known as the cosmic distance ladder. Her work made it possible to determine the accurate scale of the Milky Way, identify other galaxies beyond it, and eventually measure the expansion of the Universe itself. In this colloquium, Dr. Tansu Daylan and several members of the AstroMusers research group in the Department of Physics will follow the developments stemming from her discovery, beginning with her meticulous analysis of variable stars and tracing how precise photometric measurements enabled a deeper understanding of stellar evolution, including the formation and cooling of white dwarfs. The discussion will then move outward to the galactic scale, where Leavitt’s relation revealed the immensity of space and led to the recognition of galaxies as dynamic, independent systems. Finally, the colloquium will examine one of the most significant frontiers of modern astrophysics—the detection of dark matter—whose gravitational effects determine the rotation of galaxies, the binding of clusters, and the growth of large-scale cosmic filaments, even though it emits no light of its own. Across these themes runs a single unifying idea: careful observation and the disciplined use of light as data remain central to how astronomers uncover both the visible and hidden structure of the Universe.
This event will take place in Seigle Hall, Room 206. Download a campus map here.
Dr. Tansu Daylan is an assistant professor in the Department of Physics and leads a research program focused on atmospheric characterization of exoplanets and the astrophysical signatures of dark matter. He is the Principal Investigator for one of the Wide Field Science Programs of NASA's upcoming Roman Space Telescope. Members of his AstroMusers research group, Aavik Wadivkar, Bryce Wedig, and Dr. Chris Cappiello, work on contemporary astrophysical problems. Aavik is an undergraduate majoring in astrophysics, doing a research project on planets transiting white dwarfs. Bryce is a fourth-year PhD student in physics working on cosmic gravitational lenses, and Chris is an Ed Jaynes postdoctoral fellow in the Department of Physics focusing on particle properties of dark matter.
Dr. Chris Cappiello is an Edwin Thompson Jaynes Postdoctoral Fellow in the Department of Physics. He received his PhD in 2021 from Ohio State, after which he was a postdoctoral fellow at Queen's University in Kingston, Canada, before joining the Department at WashU in 2024. His research focuses on dark matter theory, finding new ways to use particle detectors, telescopes, and astrophysics generally to search for dark matter. Although he is a theorist, Chris has collaborated with experimental groups in the past, identifying new models of dark matter that their detectors could search for.
Bryce Wedig is a fourth-year PhD candidate in Physics studying dark matter using space telescopes. He studied physics and philosophy at Kenyon College and philosophy of physics at the University of Cambridge.
Aavik Wadivkar is a sophomore undergraduate student studying Astrophysics and Philosophy. He's involved in exoplanet research, searching for planets orbiting around White Dwarfs and contributing to ExoCore, a NASA-funded curriculum of open science for the field of exoplanets. He also acts as President of WashU Satellite, an undergrad-led engineering design team that develops and builds satellites and space-ready science missions for WashU research. He's passionate about the intersection of science and philosophy and how we understand the world around us.
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