At the center of our galaxy, a massive gas disk orbits a supermassive black hole. Its pull is uneven from all sides, so it can slowly twist the orbits of stellar pairs. Over time, such a pair may drift too close to the hole and be torn apart by tidal forces (the difference in gravitational pull on the near and far side, like the Moon causing tides on Earth).

In a new study using computer simulations, researchers calculate that if such a disk existed about 5 million years ago, when new stars were being born in the galactic center, it could have disrupted about a hundred binary systems. In each case, one star was captured into a very tight orbit, while the other was ejected at enormous speed. The fastest known runaway star — S5-HVS1 — is racing at 1800 km/s and most likely originated this way. The disk's gravitational rudder explains not only lone hypervelocity stars but also a whole swarm of faint objects hugging the black hole.