Asteroid 2023 BU passed close to Earth: What to know

Our solar system is teeming with space rocks.

Fortunately, NASA and other agencies are closely tracking asteroids traversing Earth’s cosmic neighborhood, discovering hundreds more each year, and have found none that could potentially threaten our planet for the next 100 years or so.

On Jan. 26, a small asteroid (“about the size of a panel van,” NASA said) passed just 2,200 miles from Earth. Because it’s so small, the rock, dubbed “2023 BU,” was not found until January 21 by an amateur astronomer while traveling nearby. It was never a threat. Even if it did hit Earth, it would “decay largely harmlessly in the atmosphere,” NASA explained(Opens in a new window).

Here’s what you need to know about asteroid 2023 BU (which passed through the southern tip of South America) and other near-Earth asteroids:

1. NASA has not issued an Asteroid 2023 BU warning

NASA’s Jet Propulsion Laboratory, which operates the agency’s Center for Near Earth Object Studies(Opens in a new window)track the passing asteroids relatively close to Earth, although many of these rocks are millions of miles away because space is vast. Technically, a near-Earth object (NEO) is one that moves within about 30 million miles(Opens in a new window) the orbit of our planet around the sun.

So 2023 BU easily qualifies as a near-Earth object. But because it was never a threat — it had no chance of hitting Earth and was too small to pose a threat — NASA and other US agencies never issued a warning about it. You may have read sensational headlines “NASA warns that asteroid flies close to Earth” but that’s just wrong. A warning would be a serious escalation implying a threat.

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“We’ve never really issued a warning,” NASA Planetary Defense Officer Lindley Johnson told Mashable in 2021. If a rock larger than 30 feet wide turns out to have a greater than one percent chance to hit Earth, NASA will issue an official warning to the White House and other government leaders, who will then assess the situation and inform the public of a possible strike.

In this case, NASA released some brief information(Opens in a new window) on 2023 BE and how it was detected. Indeed it is an interesting little event. “In fact, this is one of the closest approaches of a known near-Earth object ever recorded,” NASA engineer Davide Farnocchia said in a statement.

2. Asteroids are not often a threat to Earth

In general, the larger the asteroid, the greater the threat it poses to Earth.

The rock that likely wiped out the dinosaurs is in the largest class of asteroids, meaning it’s over 0.6 miles wide. The Dino Rock was a behemoth about six miles wide(Opens in a new window). But these are extremely rare visitors. As Mashable reported last year:

• No known asteroid over 460 feet in diameter will threaten Earth in the next century or so (a rock about 460 feet in diameter is an asteroid large enough to cause significant devastation).

• Impacts from objects about 460 feet in diameter occur every 10,000 to 20,000 years.

• “Dinosaur-killing” impacts of rocks perhaps half a mile or more in diameter occur on timescales of 100 million years.

Importantly, asteroids smaller than 460 feet can still pose a major threat. Even an asteroid about 100 to 170 feet in diameter could destroy a place like Kansas City,(Opens in a new window) Home to half a million people. Therefore, the elevations for large and “small” rocks are crucial.

A graphic from NASA showing known asteroids (blue dots) in our solar system.
Photo credit: NASA

3. Astronomers are on the lookout for potentially dangerous asteroids

Large, specialized telescopes are dedicated to the search for new near-Earth asteroids. There’s taxpayer money involved: NASA has a congressional mandate to find 90 percent of all space rocks 460 feet wide or wider.

• Pan STARRS: Maui’s Panoramic Survey Telescope and Rapid Response System consists of two telescopes that look up at the sky, looking for unusual movements. Using its keen vision, Pan-STARRS found 253 of the 456 near-Earth asteroids larger than 460 feet across discovered in 2021(Opens in a new window)and has been a leader in these detections for the past decade.

• Catalina Sky Survey: The three telescopes in this survey are located in the Santa Catalina Mountains in Arizona. While Pan-STARRS tends to find more NEOs taller than 460 feet (or 140 meters), Catalina finds slightly more NEOs overall(Opens in a new window). That’s a good thing, because something under 140 meters is still quite capable of devastation.

• ATLAS: The Last Alert System for asteroid impacts on Earth acts like a giant floodlight, scrutinizing the Earth closely. It consists of three telescopes: one in Hawaii, one in Chile and one in South Africa, which can scan the entire sky each night. You may spot something about 65 feet away in a few days.

So far, astronomers have found about 40 percent of rocks 460 feet in diameter or larger, with hundreds more being found each year. They have now identified an estimated 95 percent of the largest “planet killer” asteroids.

A graph showing how many near-Earth asteroids have been discovered so far.
Photo credit: NASA

Importantly, some smaller asteroids will inevitably slip through the survey cracks. This is why other astronomical sleuths are so valuable. Amateur astronomer Gennadiy Borisov found 2023 BU, informed other astronomers, and it was reported to an international organization called Minor Planet Center, which tracks such objects(Opens in a new window). A few days later, NASA’s Center for Near Earth Object Studies confirmed the asteroid and its trajectory.

So when you hear about an asteroid “heading for Earth,” remember that this is unlikely to pose a threat (asteroids regularly approach Earth by millions of miles), experts are closely watching the sky, and if something big, Earth should actually threaten, space agencies like NASA will be around to provide coherent information on where to go (probably the vast ocean) and what to do (usually nothing).

Enjoy the sky. Yes, have a healthy respect for the great space rocks orbiting the sun. But when you see an asteroid warning on the internet, you should have a strong dose of skepticism.

This story has been updated with additional information about Asteroid 2023 BU.