YR4's odds jumped to a 1-in-32 chance of impact, though that number will likely fall as the asteroid continues to be monitored.

Space agencies have systems in place to spot, track, and forecast the future orbits of potentially hazardous asteroids.

There's the Yarkovsky effect, too – a change in rotation produced by contrasts in light and temperature. Because dark comets don't have tails that we can detect, the smoking gun that there's ...