Shan-Shan Zhao

The farther apart the antennas, the finer the details they pick up. By merging signals, astronomers effectively turn multiple dishes into a single telescope as big as the distance between them. Add a lunar antenna to the Earth-based array, and you get a virtual eye 384 000 km wide.

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.