At the center of the distant galaxy NGC 1052, an invisible engine is at work. It accelerates clouds of gas to speeds at which sulfur oxide (SO) molecules begin to absorb radio waves. Astronomers caught this radiation using a network of Korean radio telescopes operating as a single instrument the size of a continent.

The supermassive black hole at the galaxy's core is surrounded by a rotating ring of gas and dust — a torus. A plasma jet emerging from the vicinity of the hole plows into this ring. The impact heats the gas, and SO molecules evaporate from the surfaces of dust grains. Some clouds are carried away by the jet, while others, having lost speed, fall back toward the hole.

Previously, water vapor masers, natural cosmic amplifiers of radio waves, had been found in the same region. Now it turns out that both SO molecules and H2O masers arise in the same collision zone where the jet meets the torus. The only difference is that water amplifies radiation, while sulfur oxide absorbs it.

Thus, astronomers have for the first time peered into a region less than half a light-year across around the black hole. It turns out that gas there is not simply falling into the hole but participates in a complex cycle: the jet flings it outward, gravity pulls it back. This "breathing" process may govern the black hole's growth and the birth of new stars in the galaxy.