Zong-Hong Zhu

The universe is full of black holes, but middleweights long eluded detection. Now distortions in radio signals have given them away, as if invisible masses altered the voice of distant bursts. These could be Big Bang relics hiding in dark matter.

Astronomers cracked the flare pattern of a distant galaxy. A tiny orbiting object repeatedly punches through a gas cloud — the remains of a torn-apart star. The cloud is bent, so some bursts shine brighter, others dimmer. This on-off rhythm unveils the central black hole's spin. In a few decades, th