Earth had a near-miss incident with a large asteroid on Wednesday. A 100-metre-wide (328-feet-wide) asteroid passed just 70,000 kilometers from Earth. It was discovered by the Brazilian SONEAR survey just days ago, and its presence was announced mere hours before it zoomed past our planet.
“The closest it came to Earth was just under 45,000 miles, a safe distance, but still much less than the distance between the Earth and moon,” Astronomy magazine said. The moon is about 239,000 miles from the Earth.
The rock was a shock: “It snuck up on us pretty quickly,” Michael Brown, an associate professor in Australia with Monash University’s School of Physics and Astronomy, told the Washington Post. “People are only sort of realizing what happened pretty much after it’s already flung past us.”
— ASAS-SN (@SuperASASSN) July 25, 2019
The asteroid, designated 2019 OK, is not a threat to Earth right now. However, 2019 OK and other near-Earth asteroids do pose a genuine risk.
However scary it may sound, however, asteroid flybys are “routine,” Richard Binzel, a professor of planetary science at the Massachusetts Institute of Technology told USA TODAY. “Schoolbus-sized objects pass closer than the moon every week. (The asteroid) may have been about the size of a football field and a football-field sized object passes inside the moon’s orbit one or more times per year,” he said.
According to the International Astronomical Union’s Minor Planet Center, the asteroid was first observed on June 28 by the Pan-STARRS observatory in Hawaii. The actual size and path of the asteroid, however, wasn’t detected until the SONEAR Observatory in Brazil picked it up just before it passed by Wednesday night.
Had it hit the Earth, “it would have gone off like a very large nuclear weapon” with enough force to destroy a city, Brown told the Post.
Binzel told USA TODAY that the region damaged would be “an area comparable to inside the Washington beltway.”
How did we miss it? Basically it was hard to spot due to its (relatively) small size, eccentric orbit and its fast speed, Brown said. Binzel elaborated on this point, noting that the object “is below the long-term advance detection limit of any system in place.”
Typically, asteroids are so far from Earth that they resemble stars, rather than the craggy rocks they are. However, because asteroids travel around the Solar System, they move relative to the distant stars. Thus astronomers can discover asteroids by taking sequences of images and looking for objects that move from image to image.
Asteroids that come within 5 million miles (8 million km) of Earth’s orbit are deemed potentially hazardous by NASA even if they have a pretty slim chance of impacting Earth. However, tracking all near-Earth objects helps the agency study ways to protect our planet in the event a hazardous object were to pose a threat.
Earth had a close call in April, when asteroid 2019 GC6, a house-size space rock, flew by our planet at a distance of 136,000 miles (219,000 km). The potentially hazardous space object was detected just nine days before the flyby.