Astronomers are monitoring X-ray flares from the vicinity of a black hole at the center of a galaxy. These flares repeat with a certain rhythm, like heartbeats. Normally, as a star approaches a black hole, the rhythm speeds up — just as a pulse quickens when running. But at the black hole 'Ansky,' the rhythm is slowing down. Each successive beat lags more than the previous one: over a day, the gap grows by almost half an hour. It's as if the heart, instead of racing under stress, were slowing to a halt.

Nobody yet knows why this rhythm is slowing. Perhaps we're missing some fundamental process — for instance, an unknown way of losing energy.