Thanks to powerful telescopes that can detect large objects at extreme distances, we earthlings have a pretty good idea of the space rocks that pose threats to Earth. However, every once in a while nature reminds us that it still has some potentially apocalyptic surprises in store, and that’s exactly what happened yesterday when an asteroid as large as 427 feet across appeared seemingly out of nowhere, speeding past Earth at an alarmingly close distance.

The rock, now named 2019 OK, came within a scant 43,500 miles of Earth, which is far closer than the Moon is to Earth, and astronomers didn’t even know it was there until it was already upon us. The Sun, it turns out, is to blame for our lack of awareness.

The rock’s trajectory put it on a path that sent it straight towards Earth from the direction of the Sun. Because of how bright our host star is, scientists couldn’t spot the asteroid within its intense glare, making it impossible to see it ahead of time. Had it been on a true collision course with Earth, we would have been powerless to stop it.

The rock wasn’t a supersized “planet-killer,” but it would have absolutely done some serious damage if it struck a populated area. Scientists have compared its potential impact force to that of a “very large” nuclear weapon, so to say that we got lucky on this one would be a major understatement.

Asteroids as large as 2019 OK don’t show up in Earth’s immediate vicinity all that often. We do see them from time to time, but such a close pass with absolutely zero warning is indeed incredibly rare. The good news — aside from the obvious fact that it didn’t strike Earth — is that now that astronomers know it exists they can study it and plot its course, giving us a far earlier warning if it ever ends up in our neck of the woods again.