The Black Hole Photon Ring: Understanding M87* and Future NASA Observations

Explore the fascinating physics of black hole imaging in this scientific lecture from the Workshop on "Lensing and Wave Optics in Strong Gravity" at ESI. Delve into the groundbreaking first images of the M87* supermassive black hole, examining the bright ring surrounding its event horizon and the theoretically predicted "photon ring" phenomenon. Learn how multiple mirror images form from photons orbiting the black hole, revealing crucial information about space-time geometry near the event horizon. Discover how the photon ring, though not yet directly observed, could serve as a critical test of Einstein's general relativity theory and understand its significance as a primary research target for NASA's upcoming Black Hole Explorer (BHEX) mission.