Bart Ripperda

In 2019, astronomers unveiled the first-ever image of a black hole's shadow — a dark void encircled by a lopsided orange ring. This is the supermassive black hole at the heart of galaxy M87, 55 million light-years away. The ring isn't just glowing: one side is noticeably brighter than the other, like a campfire burning unevenly, with flames leaping higher on one side.

Radio telescopes scattered across the globe pick up waves from distant black holes. But two telescopes placed almost side by side see only a blurry blob — fine details are beyond them. Usually, such pairs are considered useless and discarded. But that's a mistake: even a blurry blob holds clues.

A radio telescope picks up a signal from the center of the Milky Way. The source MAXI J1744-294 flares in X-rays and radio waves, but where it actually resides is a mystery. It could be near the black hole, or it could just lie along the same line of sight, thousands of light-years away.

At the center of the Milky Way lies the supermassive black hole Sagittarius A*. It is four million times more massive than the Sun, but by cosmic standards it behaves quietly: it only occasionally flares up when it swallows a clump of gas.

A boiling pot, a gust of wind, a wisp of smoke from a campfire — all obey equations that mathematicians call 'nonlinear and dissipative.' In plain terms, energy is lost to friction, and parts of the flow influence each other so strongly that predicting the motion ahead of time is a task on the edge of feasibility.

In April 2021, the antennas of the Event Horizon Telescope (EHT)—a global network of millimeter-wave radio telescopes — zeroed in on a tiny spot in the constellation Virgo.