Xiaopeng Cheng

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.

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.

The plasma jet from the center of a distant galaxy is like a river that flows from its source and gradually becomes clear. Near the black hole, the flow is dense and opaque to radio waves, like muddy water.

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.