Nasa said the newly discovered asteroid would pass 2,200 miles (3,600km) above the southern tip of South America at 7.27pm US eastern time on Thursday (12.27am GMT on Friday).
If the space rock, which is estimated to be 11.5 to 28 feet (3.5 to 8.5 meters) across, did head for Earth, it would transform into a fireball once it entered the atmosphere and disintegrate. Any remaining debris would fall to the ground as small meteorites, according to the space agency.
Nasa’s impact hazard assessment system, called Scout, quickly ruled out a strike, said its developer, Davide Farnocchia, an engineer at the agency’s Jet Propulsion Laboratory in Pasadena, California.
“But despite the very few observations, it was nonetheless able to predict that the asteroid would make an extraordinarily close approach with Earth,” Farnocchia said. “In fact, this is one of the closest approaches by a known near-Earth object ever recorded.”
Earth’s gravity changes the trajectory of asteroids, but 2023 BU will come so close to our planet that its orbit around the sun will change after the encounter.