Two small asteroids in unrelated orbits will pass within the moon's distance of the Earth on Wednesday, according to NASA.
It's an unusual event that shows the need for closer monitoring of near space for Earth-threatening encounters, a scientist with the program said.
The objects don't pose a threat to Earth, and they will not be visible to the naked eye, said Donald Yeomans, manager of NASA’s Near Earth Program, which tracks potentially hazardous asteroids and comets within 28 million miles of Earth.
The objects will visible from Earth as tiny specks of light with the help of moderate-sized amateur telescopes, he said.
Near-Earth asteroid 2010 RX30, which is estimated to be 32 to 65 feet in size, will pass within 154,000 miles of Earth at 5:51 a.m. ET Wednesday. The second object, 2010 RF12, estimated to be 20 to 46 feet in size, will pass within 49,088 miles of Earth at 5:12 pm ET.
In case you were wondering, that means the two asteroids will pass within 0.6 and 0.2 lunar distances from the Earth, respectively. The first will be closest to Earth over the north Pacific, and the second, over Antarctica.
Roughly 50 million objects pass through near-Earth space each day, Yeomans said. But what makes this situation noteworthy is that these two asteroids are passing so close to Earth on the same day and that NASA spotted them so far in advance.
"Things like this happen every day that we simply don’t know about because we don’t have the telescopes large enough to find them or surveys that are looking full-time," he said. "This demonstrates the system's working on some level, but we need larger telescopes and more of them to find objects that are coming this close."
The Catalina Sky Survey near Tucson, Arizona, discovered both objects Sunday morning during a routine monitoring of the skies, NASA said.
The Minor Planet Center in Cambridge, Massachusetts, first received the observations Sunday morning, determined preliminary orbits and concluded both objects would pass within the distance of the moon about three days later.
Yeomans described the discovery as a warning shot in a field of study of low-probability events that have global, high-impact consequences. He said that it was only when scientists began looking for near-Earth objects in the 1990s that they realized there was a "problem."
"We have only recently appreciated how many of these objects are in near Earth's space and [it's] best that we keep track of them and find them," he said. "I think this is Mother Nature's way of firing a shot over the bow and warning Earth-based astronomers that we have a lot of work to do."