Peng-Cheng Li

A black hole isn’t a perfectly smooth ball. Einstein’s theory allows invisible 'hair' — clumps of scalar field — to swarm around it, warping spacetime. The shadow — the dark region from which light can’t escape — was predicted by Penrose in the 1960s.

A pair of black holes circles in a dance, gradually drawing closer. They lose energy and spin — a process known as angular momentum radiation. In standard Einstein theory, only gravitational waves carry away angular momentum.