A long exposure photo showing the trajectory of asteroid 2024 BX1 just before impact.Changes in brightness are caused by the asteroid’s rotation
L. Buzzi, Schiaparelli Observatory, Italy (MPC 204)
The asteroid that crashed into Earth’s atmosphere earlier this year was spinning once every 2.6 seconds, faster than any asteroid we know of.
The object, called 2024 BX1, was probably less than a meter wide and entered Earth’s atmosphere on January 21. It collapsed over Berlin, Germany. Some debris survived the fireball and was recovered. This is a rare example of a tracked asteroid fall, where the incoming rock was discovered before it hit Earth, in this case just three hours before impact.
Maxime Devogele and colleagues at the European Space Agency’s Near-Earth Object Coordination Center in Italy captured images of the asteroid before impact. Despite moving at approximately 50,000 kilometers per hour, due to its elongated shape, changes in brightness due to rotation were particularly noticeable in these images.
These brightness changes correspond to a rotation time of 2.588 seconds, which corresponds to about 30,000 revolutions per day. “That’s the fastest [spin] We have observed this before,” says Devogele.
Asteroids rotate for a variety of reasons, including collisions early in their lives. Generally, a space rock larger than 1 kilometer cannot rotate more than once every 2.2 hours, as it would break apart. However, smaller asteroids like 2024 BX1 can withstand much faster rotations because they are more compact. “They have internal strength, so they can rotate faster,” says Devogerre.
Measuring the rotation of such objects could be useful for planetary defense, allowing us to learn how strong small asteroids are and what their chances of surviving a passage through Earth’s atmosphere are. . “If you have hard snow, it will react differently than if you have snow that has no internal strength,” Devogele says.
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