An asteroid about the size of a refrigerator shot past Earth last week, and astronomers didn’t know the object existed until hours after it was gone.
It was a close call (from a cosmic perspective); the space rock’s trajectory on Oct. 24 carried it over Antarctica within 1,800 miles (3,000 kilometers) of Earth — closer than some satellites — making it the third-closest asteroid to approach the planet without actually hitting it, CNET reported.
Scientists were unaware of the object, dubbed Asteroid 2021 UA1, because it approached Earth’s daytime side from the direction of the sun, so the comparatively dim and small visitor went undetected until about 4 hours after passing by at its closest point, according to CNET.
But with a diameter of just 6.6 feet (2 meters), UA1 was too small to pose a threat. Even if it had struck Earth, most of its rocky body would have burned away in the atmosphere before it could hit the ground, CNET reported.
Comets and asteroids that orbit within our cosmic neighborhood, approaching Earth within 1.3 astronomical units (120.9 million miles, or 194.5 million kilometers) are known as near-Earth objects (NEOs), according to NASA’s Center for Near-Earth Object Studies (CNEOS). NASA uses telescopes on the ground and in space to find and monitor NEOs; to track their orbits and identify their size, shape and composition; and to pinpoint potentially hazardous objects, managing these efforts through the agency’s Planetary Defense Coordination Office.
For an object to be considered dangerous, it has to measure at least 460 feet (140 m) in diameter, NASA says. UA1 may not have been big enough to threaten the planet, but what about bigger asteroids that might be headed our way? NASA is also investigating defensive technologies for protecting Earth from possible collisions with larger space rocks, through deflection.