Scientists have identified more than 30,000 near-Earth objects (NEOs) to date. So what are the largest "potentially hazardous" NEOs predicted to have a close encounter with Earth in 2023?
The term "near-Earth object" is used to refer to any cosmic body whose orbit comes close to that of our planet, in astronomical terms. The vast majority of NEOs are asteroids—most of which are small—although more than a hundred comets are also included in this category.
Some NEOs are classified as "potentially hazardous"—a designation given to those with orbits that come within 0.05 astronomical units (around 4.6 million miles) of Earth's path around the sun and are estimated to measure more than 140 meters (around 460 feet) in diameter.
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None of the potentially hazardous objects that are known to scientists have any realistic chance of colliding with the Earth in the foreseeable future. The potentially hazardous designation simply means that over many centuries and millennia the orbit of these objects may evolve into one that has a chance of impacting Earth.
In the event of an impact, potentially hazardous objects are large enough to produce significant damage to our planet on at least a regional scale.
Largest NEOs to Pass Earth in 2023
Below is a list of the largest potentially hazardous NEOs, all of which are asteroids, to make a close approach to Earth—i.e., they came within 0.05 astronomical units of our planet—in 2023, according to data from NASA's Center for Near Earth Object Studies (CNEOS) database.
363505 (2003 UC20)
This is potentially the largest asteroid that will make a close approach to Earth next year. The CNEOS database indicates that it measures around 1.2 miles, or 6,230 feet, across, which makes it more than twice as large as the Burj Khalifa is tall. The Burj Khalifa in Dubai is the tallest building in the world. The asteroid will make its close approach on November 2, coming as close as 3.2 million miles to Earth.
199145 (2005 YY128)
This asteroid is estimated to measure between 1,870 and 4,265 feet across, meaning it could be slightly larger than Angel Falls in Venezuela—the world's largest uninterrupted waterfall—at the upper end of this range. This object is set to fly past us on February 16, coming within a minimum distance of around 2.8 million miles.
An artist's illustration shows an asteroid in space. Scientists have identified more than 30,000 near-Earth objects to date. An artist's illustration shows an asteroid in space. Scientists have identified more than 30,000 near-Earth objects to date. iStock436774 (2012 KY3)
The CNEOS database indicates that 436774 (2012 KY3) measures between 1,771 and 3,937 feet across, making it about as long as the Navy Pier in Chicago. This NEO is scheduled to make its close approach on April 13, at which point it could come as close as 2.9 million miles to our planet.
139622 (2001 QQ142)
This asteroid is thought to measure between 1,738 and 3,937 feet, meaning it could also be roughly similar in size to the Navy Pier, at the upper end of this scale, or about two and half times as tall as the Willis Tower in Chicago. It will zoom past Earth on December 6, coming around 3.4 million miles from us.
349507 (2008 QY)
Data indicates 349507 (2008 QY) measures anywhere from 1,706 to 3,937 feet across, meaning it is also similar in size to 436774 (2012 KY3) and 139622 (2001 QQ142) at its upper limit. This space rock will make its closest approach to Earth on October 3, coming as close as 3.9 million miles to our planet.
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