Mohsen Fathi

In 2019, the Event Horizon Telescope gave humanity the first image of a black hole shadow — a fiery ring around the abyss at the center of galaxy M87. This gravitational self-portrait, painted by the light of infalling plasma, instantly became an icon of modern astrophysics.

The gravity of a black hole creates a curvature of spacetime, acting like a lens: light from a distant galaxy splits in two, stretching into arcs. Dark matter around the hole barely changes the picture, as if a transparent curtain was added to a window pane.

At the center of most galaxies lurk supermassive black holes — the overlords of gravity. Since 2019, thanks to interferometry with very long baselines, we’ve glimpsed their shadows: dark silhouettes set against a blazing gas backdrop. But what exactly is painting that shadow?