A small asteroid about the size of a truck passed within 2,200 miles of Earth on Thursday. At 7:27 p.m. Eastern time, it sped over the southern tip of South America in “one of the closest approaches by a known near-Earth object ever recorded,” Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory, says in a statement.
The asteroid, called 2023 BU, was only recently discovered: Scientists did not know it existed until Crimean amateur astronomer Gennadiy Borisov spotted it on January 21. He has been credited with finding several other comets and asteroids, including the first interstellar comet in 2019, named 2I/Borisov.
Within three days, dozens of observations from around the world helped determine the asteroid’s orbit, highlighting the importance of both seasoned and amateur astronomers worldwide.
“The big professional search programs that NASA is funding are doing, by far and large, the heavy lifting in discovering new objects,” Farnocchia tells the New York Times’ Anastasia Marks. “But that doesn’t mean that we cannot use help from additional people, which includes professional astronomers from other countries but also amateur astronomers. We like to get as many as possible so that we can get the best possible estimate of the trajectory.”
NASA’s Scout impact hazard assessment system determined that the object would not make an impact. Even if it did, the estimated 11.5- to 28-foot-wide asteroid would have disintegrated, mostly harmlessly, in the atmosphere, per the agency.
Still, many asteroids that are as yet undiscovered could cause significant damage to Earth, Don Pollacco, an astronomer at the University of Warwick in England, tells BBC News’ Jonathan Amos. “Indeed, many scientists think we could be due [for] such an event,” he tells the publication.
Asteroids that could cause global devastation have mostly all been accounted for, but astronomers have only found some 40 percent of the smaller ones that could lead to mass casualties, per BBC News. The threat of such an impact led NASA to test its ability to knock an asteroid off course last September in its Double Asteroid Redirection Test (DART). The agency successfully altered the asteroid Dimorphos’ orbit by 32 minutes.
2023 BU was both smaller and dimmer than an Earth-threatening object, which would have been spotted much sooner. Still, the asteroid passed near enough to Earth that it came about ten times closer to the planet’s surface than geosynchronous satellites—those that orbit at the same rate as the planet’s spin.
The Earth’s gravity causes any asteroid in its proximity to have a change in trajectory, but 2023 BU will experience a particularly vast change. After passing by us, its path around the sun has elongated and lengthened from 359 days to 425 days, per NASA.
While 2023 BU’s proximity to Earth was unusual, smaller objects pass by us fairly frequently, per the Times.
“This case might seem exceptional, but in fact, objects of a similar size come this close to Earth about once a year on average,” Farnocchia tells the publication. “So this is not an exceptional event. It’s not an everyday event, but it’s something that happens regularly.”