Interferometry and the Event Horizon Telescope | AI Learning Guide

Imaging a black hole requires a telescope as large as Earth. The Event Horizon Telescope achieves this by linking radio dishes globally using atomic clocks. The dark spot in their images isn't the event horizon, but the photon shadow—a region where light is swallowed, silhouetted against glowing gas.

0:00 / 0:00

Auto-play

Very Long Baseline Interferometry

To resolve the tiny angular size of a black hole shadow, we need a telescope aperture the size of Earth. VLBI combines data from radio telescopes worldwide, synchronized by atomic clocks, effectively creating a planet-sized interferometer.

The Photon Shadow

The dark region in EHT images is not the event horizon itself, but the 'photon capture region' or shadow. It is caused by photons being captured by the black hole's gravity, leaving a dark silhouette against the bright background emission.