Astronomers learned of its existence just hours after it made a close pass by our planet. The object was about the size of a refrigerator.
Near the end of October 2021, an asteroid about the size of a refrigerator passed close to Earth. The curiosity, however, is that astronomers learned of its existence only a few hours after its disappearance. It was, from a cosmic perspective, a close call. The trajectory of the space rock pushed the object towards Antarctica at about 3 thousand kilometers from our planet, that is closer than some satellites. According to the CNET website, it would have been the third asteroid to have come closest to the globe without hitting it.
The asteroid that approached Earth
Scientists would not have noticed the asteroid, which was later dubbed Asteroid 2021 UA1, because it would have approached the daytime side of the Earth from the direction of the Sun. The rather small space rock would thus have escaped detection until about 4 hours after passing at its closest point to our planet. In any case, with a diameter of only 2 meters, UA1 was too small to pose a threat. Even if it had hit Earth, most of its rocky body would have disintegrated in the atmosphere before it could hit the ground.
How Near-Earth Asteroids Are Tracked
Comets and asteroids that orbit near Earth, approaching the globe within 1.3 astronomical units (194.5 million kilometers) are known as NEOs, near-Earth objects. Nasa uses telescopes both on the ground and in space to find and monitor NEOs; to track their orbits and identify their size, shape and composition; and to detect potentially hazardous objects, managing these efforts through the agency's Planetary Defense Coordination Office.
For Nasa to consider an object hazardous, it must measure at least 460 feet (140 m) in diameter. Nasa is also investigating defensive technologies to protect Earth from possible collisions with larger space rocks through deflection. For example, the Double Asteroid Redirection Test (DART), which was launched on Nov. 24, is testing a method of deflecting asteroids by hitting them with high-speed remote-controlled spacecraft.
Among the NEOs that are constantly monitored, however, is asteroid 4660 Nereus, which will come as close as 12 times to Earth in the next few years. Its size is similar to the more famous Bennu, which is expected to approach our planet in 2135.