Topline: An asteroid that could have destroyed an entire city passed by Earth earlier this week—and scientists didn’t notice until it was just a day away from closely passing Earth.
- The rock—named Asteroid 2019 OK—was 187 to 427 feet (or 57 to 130 meters) wide. It wasn’t big enough to cause dinosaur-level extinction, but scientists have referred to it as a “city killer” that could have leveled an entire city.
- At its closest, it flew 45,000 miles (73,000 kilometers) from Earth. To put that into perspective, that’s less than one-fifth the distance to the moon, according to The Washington Post.
- The asteroid caught scientists by surprise, with astronomy teams in Brazil and the U.S. only detecting the asteroid on Wednesday, just a day before it flew close to Earth.
Asteroid 2019 OK was able to evade observers because it’s relatively small compared to other major asteroids. And it was traveling fast at about 54,000 miles per hour. Plus, it only reflects enough light to be picked up by a telescope when it’s a few days out from Earth, and even then astronomers have to be looking at the right spot at the right time.
Michael Brown, an associate astronomy professor at Monash University in Australia, noted that just three days before that it passed Earth, Asteroid 2019 OK was 1,000 times fainter, making it harder to spot.
Brown added that for the past month, the asteroid has been relatively close to the sun, so it has only been visible around twilight.
NASA is already detecting larger asteroids than Asteroid 2019 OK. In 2005, Congress directed the space agency to find at least 90% of potentially dangerous asteroids larger than 140 meters by the end of 2020 (Asteroid 2019 OK was only 130 meters wide). But it has only identified about a third of those so far, according to Gizmodo.
Asteroid 2019 has already passed Earth, so it isn’t a threat right now, but others like it could be.
I’m a San Francisco-based reporter covering breaking news at Forbes. Previously, I’ve reported for USA Today, Business Insider, The San Francisco Business Times and San Jose Inside. I studied journalism at Syracuse University’s S.I. Newhouse School of Public Communications and was an editor at The Daily Orange, the university’s independent student newspaper. Follow me on Twitter @rachsandl or shoot me an email email@example.com.