In space, an asteroid that comes within 120,000 miles of Earth is considered a close call.
So we should feel lucky that a flying boulder whizzed past us Sunday without incident, especially considering that scientists didn't see the massive rock coming until the last minute. The asteroid, named 2018 GE3, was the size of a football field, measuring about up to 361 feet in diameter.
Because asteroids are relatively small and dark, LiveScience reports, it can be hard to predict when one will approach our planet — which is a fairly rare occurrence anyway. This most recent asteroid passed at half the moon's distance from Earth — about 119,500 miles — but the Catalina Sky Survey didn't spot it until a few hours before because the massive rock reflected so little light.
Telescopes used by NASA are generally on the lookout for much larger and potentially extremely dangerous flying objects, reports LiveScience, so it's easy for skywatchers to miss smaller asteroids that would have only a, say, mildly devastating effect on impact. So rest assured: If a truly enormous asteroid were on its way to slam into Earth, NASA would let you know.