An asteroid the size of a refrigerator shot past Earth last week, and astronomers did not know the object existed until hours after it was gone.
It was a close call (from a cosmic perspective); the orbit of the space rock on October 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, It reported CNET.
Scientists were unaware of the object, called Asteroid 2021 UA1, because it was approaching Jordens day side from the direction of the sun, so that the relatively dim and small visitor remained undetected until about 4 hours after passing the nearest place, according to CNET.
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But with a diameter of only 6.6 feet (2 meters), UA1 was too small to pose a threat. Even if it had hit the Earth, most of its rocky body would have been burned away into the atmosphere before it could hit the Earth, CNET reported.
Comets and asteroids the orbit within our cosmic quarter approaching Earth within 1.3 astronomical units (120.9 million miles or 194.5 million kilometers) is known as near-Earth objects (NEOs), according to NASA’s Center for Near-Earth Object Studies (CNEOS). NASA uses telescopes on Earth and in space to find and monitor NEOs; to trace their trajectories and identify their size, shape and composition; and to locate potentially dangerous objects, directing those efforts through the Agency’s Planetary Defense Coordination Office.
For an object to be considered dangerous, it must be at least 460 feet (140 m) in diameter, NASA says. UA1 may not have been large enough to threaten the planet, but what about larger asteroids that may be on their way to us? NASA is also investigating defensive technologies to protect Earth from possible collisions with larger space rocks through deflection.
The Double Asteroid Redirection Test (DART), scheduled for launch on November 24, will test a method of redirecting asteroids by hitting them with high-speed remote-controlled spacecraft. NASA representatives said in a statement. Scientists will send the DART spacecraft rushing into the near-Earth binary asteroid Didymos, which is shaped like a spinning top and has two bodies; the largest measures about 2,600 feet (780 m) in diameter, and its smaller moon song measures about 520 feet (160 m) in diameter.
Didymos came closest to Earth in 2003, skimming it at a distance of about 4.5 million miles (7.18 million km), but it typically orbits the sun just outside the Earth’s orbit, according to NASA. Although Didymos does not threaten Earth, it is almost the right size to test whether the collision can push a dangerous NEO enough to divert it from a collision course with Earth, according to the statement.
Still, to divert an asteroid, NASA would have to detect it before it hit Earth. That’s why another mission, the NEO Surveyor, is developing an infrared space telescope that can improve the chances of spying on sneaky asteroids such as UA1 approaching behind the sun, according to the University of Arizona’s Lunar and Planetary Laboratory, which is collaborating with NASA on the project.
To date, NASA has identified approximately 27,000 NEOs, of which approximately 9,800 measure at least 459 feet (140 m) in diameter and 890 measure 0.6 miles (1 km) in diameter, according to CNEOS.
While UA1 may have been a relative pip-squeak, other asteroids zooming near Earth on November 2 are significantly larger, according to NASA Jet Propulsion Laboratory’s Asteroid Watch. These five space rocks range in diameter from 56 feet (17 m), or about the length of a house, to an airplane size of 170 feet (52 m).
Fortunately, none of these space rocks will come within 515,000 miles (829,000 km) of Earth, NASA says.
Originally published on Live Science.