An enormous asteroid—big enough to leave a six-mile-wide crater and darken the world with dust if it hit Earth—will harmlessly zip by our planet on April 29. The object, called 1998 OR2, is at least a mile wide, and while it poses no threat, it will pass within four million miles of our planet—close enough to be classified by NASA as “potentially hazardous,” because it will continue to make close passes to Earth in the future as both objects orbit the sun.

“It’s just a whopping big asteroid,” says Amy Mainzer of the University of Arizona, one of the planet’s leading scientists in asteroid detection and planetary defense. “It’s smaller than the thing thought to have caused the extinction