Last Thursday, a “city-killer” asteroid buzzed by Earth, and we had no clue it was coming.

LiveScience was among the outlets breathlessly describing our close encounter with a giant speeding space-rock that took us all by surprise:

Ranging in size from 187 to 427 feet (57 to 130 meters) wide, the space rock named 2019 OK snuck up on us Thursday morning (July 25). It swung as close as 45,000 miles (73,000 kilometers) from Earth, what one astronomer told The Washington Post was “uncomfortably close.”.

If the asteroid had actually collided with Earth, the crash would have caused devastating damage, Michael Brown, an associate professor in astronomy at Monash University in Australia, wrote in The Conversation.

Astronomers in Brazil and the United States separately discovered 2019 OK a couple of days ago, but it’s surprise visit was only announced a couple of hours before it passed by. “The lack of warning shows how quickly potentially dangerous asteroids can sneak up on us,” Brown wrote.

When 2019 OK approached our planet, anyone nearby could have spotted it with a pair of binoculars as a speck of light slowly drifting across the sky, Brown wrote. But a couple of days prior, it was 1,000 times fainter and was more difficult to spot. What’s more, it was traveling really fast along an odd elliptical orbit that pushed it beyond Mars (near the asteroid belt) to within the orbit of Venus, creating a situation where it spent little time near Earth, Brown told The Washington Post.

This comes just days after a smaller, car-sized asteroid hit our planet and blew up into a spectacular fireball a couple hundred miles south of Puerto Rico over the weekend. Similarly, scientists had also just discovered that asteroid a couple of hours before it hit, but it wasn’t nearly as large as 2019 OK.