The Galactic Underworld: Finding Invisible Black Holes

Learn how to find invisible black holes by using their subtle pull on neighboring stars to identify one special object out of a billion.

The Leonard E. Parker Center for Gravitation, Cosmology & Astrophysics invites you to explore the dark side of our Galaxy with Professor Kareem El-Badry of the California Institute of Technology.

Black holes are among the most fascinating objects in the Universe, yet most of them are completely invisible. So how do astronomers find them? Learn how the Gaia mission is revolutionizing our view of the Milky Way by measuring the motions of more than a billion stars with extraordinary precision. These measurements allow us to detect the subtle gravitational pull of unseen companions—including black holes that emit no light at all. We'll discuss the discovery of Gaia BH1, the first unambiguous dormant stellar-mass black hole found in the Milky Way, and how discoveries like it are changing our understanding of how stars live, die, and produce black holes. We'll also discuss how the imminent NASA Nancy Grace Roman Space Telescope mission will carry Gaia's work forward and even discover isolated black holes.

Kareem El-Badry is an Assistant Professor of Astronomy at the California Institute of Technology and a 2025 MacArthur Fellow. His research focuses on the formation and evolution of stars and compact objects, particularly black holes, neutron stars, and white dwarfs in binarysystems. He uses large astronomical surveys—including the European Space Agency's Gaia mission—to discover rare stellar systems and to better understand how massive stars end their lives.

Please reserve your free spot for this event by September 8, 2026.

The event will be held in the UWM Lubar Entrepreneurship Center. There will be a reception at 6:30 PM, and the program starts at 7:00 PM. There will be complimentary refreshments and a bar with drinks for purchase. We look forward to seeing you there!