Asteroid 2024 BX1: From a Light in the Sky to Rocks on the Ground

Like an unexpected guest crashing a party, a 44-centimeter-sized (17-inch) asteroid slammed into Earth’s atmosphere over Germany early on January 21st, producing a spectacular fireball. What made this event even more remarkable was that the asteroid, designated 2024 BX₁, had been discovered less than 3 hours before impact.

Krisztián Sárneczky at the Piszkéstető Station of Konkoly Observatory’s Piszkéstető Mountain Station in Hungary first recorded the asteroid when it was still just an 18th-magnitude blip in the constellation Lynx. Here’s the gif time-lapse of its movement:

Sárneczky reported his observations to the International Astronomical Union’s Minor Planet Center, and they were then automatically posted to the Near-Earth Object Confirmation Page (NEOCP). Other observations began to come in as word spread.

After three reports to the page over the next 27 minutes, NASA’s Scout hazard assessment impact system automatically flagged the new object as a potential impactor. Scout continually monitors NEOCP and calculates an object’s possible trajectory and chances of colliding with Earth. Similarly, the European Space Agency's Meerkat Asteroid Guard (Meerkat for short) scans NEOCP and computes preliminary orbits and impact potentials for newly discovered objects. Both programs were crucial in refining 2024 BX₁'s orbit.

With an impact now a real possibility, urgent calls went out for follow-up observations. European astronomers — primarily amateurs — dropped what they were doing to aim their telescopes at the asteroid and make additional position measurements. Just 70 minutes after Sárneczky’s discovery, Scout reported a 100% probability of impact and narrowed down the fall location to 60 kilometers (37 miles) west of Berlin, estimating an impact time of 0:33 UT (January 21).

NASA then turned to X (formerly Twitter) and at 7:08 p.m. EST (0:08 UT) — just 24 minutes before predicted impact — posted on its @AsteroidWatch account:

Heads Up: A tiny asteroid will disintegrate as a harmless fireball west of Berlin near Nennhausen shortly at 1:32am CET. Overseers will see it if it’s clear!

Social media lit up with the news. Incredibly, those who got wind of the alert had only to walk outside at the appointed time to witness the asteroid’s crackling, tumultuous end, exactly when and where Scout had predicted. As it spalled to pieces in the atmosphere, the fireball was visible from as far away as Slovakia, according to reports in the American Meteor Society’s Fireball log.

Observers described the meteoroid’s fragmentation, but none reported any accompanying sounds. This might have indicated that it completely disintegrated with no fragments surviving the fiery plunge. Happily, that turned out to not be true.

On Thursday, January 25th, after three days of scouring the predicted fall site west of Berlin, four Polish meteorite hunters successfully recovered meteorite fragments. Some meteorite enthusiasts were a bit skeptical at first because the stones lacked the typical black, satiny fusion crust, which usually forms due to the brief but intense heating meteoroids undergo during atmospheric entry. But not all meteorites display such crust.

Achondrites known as aubrites are often light-toned and display a pale brown or light gray fusion crust. They’re also quite rare. While specimens found by the crew and others have yet to be classified, aubrites remain an intriguing possibility. Other clues seem to point in that direction, too, including a sulfurous odor, brecciated texture, and those large, white crystals, which might be enstatite, a mineral commonly found in aubrites.

The four hunters have returned to the area to look for more and have been joined by many others, among them scientific researchers. We should be seeing and hearing more very soon, including a classification.

The asteroid, 2024 BX₁, was Sárneczky’s third pre-impact asteroid discovery and only the eighth time an asteroid has been found and successfully predicted to collide with Earth. Given its tiny size, meteoroid might be a better description. His previous discovery, the similar-sized 2023 CX₁, slammed into the atmosphere on February 13, 2023, less than 7 hours after discovery. It dropped meteorites over Normandy, France. It was later classified as an L5-6 chondrite and christened Saint-Pierre-le-Viger after a nearby town. Scout was also instrumental in predicting the time and location of that fall.

It’s heartening to see how a combination of alert observers, reporting sites, and sophisticated tools like Scout worked in tandem to alert the world to potential impactors. While this impactor was small, coordinated efforts in spotting and tracking objects could in turn lead to improved mitigation strategies for going after the big ones that could cause real harm.