Scientists had already been aware that asteroids would be passing by pretty close to Earth this week, but this one somehow eluded them.
Smaller asteroids like 2019 OK are hard to detect, unlike the almost 90 percent of asteroids that are a kilometer are larger. But because it's so small, it's incredibly hard to see until right at the last minute.
The asteroid measured almost 110 yards wide, which is not large but could do a considerable amount of damage to a city.
"It would have hit with over 30 times the energy of the atomic blast at Hiroshima", Dr Duffy said.
The rock's trajectory put it on a path that sent it straight towards Earth from the direction of the Sun.
The fast-moving object was confirmed by the asteroid-hunting Sonear survey in Brazil just a day ago. Did the scene in Avengers: Endgame where Tony Stark thinks he's going to die, lost in space, give me anxiety? "It's a pretty big deal", Monash University's Prof.
ASSOCIATE PROFESSOR ALAN DUFFY, an astronomer, on Earth's close call with Asteroid 2019 OK.
According to NASA, Asteroid 2019 OK has been near Earth before, but never so close.
Consequently, astronomers across the globe have devoted considerable effort to determining the level of threat posed by near-Earth asteroids, and to identifying individual asteroids that could pose a significant threat.
The lack of warning shows how quickly potentially risky asteroids can sneak up on us.
The Earth just experienced the equivalent of strolling down the street and minding your own business when suddenly a baseball whistles by your ear.
The new document, titled 'The National Near-Earth Object Preparedness Strategy and Action Plan, ' established five strategic goals to reduce the risk of an asteroid strike.
Asteroid 2015 HM10, which is up to 360 feet wide, also flew by Earth. One strategy involves gently pushing the asteroid slowly over time off its course and away from Earth, he said.
"Asteroid 2019 OK has a very elliptical orbit, taking it from the asteroid belt beyond Mars to within the orbits of both Earth and Venus".
The US government is stepping up efforts to protect the planet from incoming asteroids that could wipe out entire regions or even continents.
According to some sources, it is the most massive asteroid which flew so close to Earth this year, and it will likely remain the only one for an extended period.