We’ve spotted a huge asteroid spinning impossibly fast

The Vera C. Rubin Observatory in Chile has spotted the fastest-spinning large asteroid ever seen. Although it measures more than half a kilometer in diameter, this asteroid rotates approximately every 1.9 minutes – a speed once thought impossible.

Dmitrii Vavilov of the University of Washington in Seattle and colleagues discovered this asteroid, along with several other surprisingly fast rotators, in data from the first nine nights of Rubin observations in late April and early May 2025. Vavilov presented the results at the Lunar and Planetary Science Conference in Texas on March 17.

During this observation period, the researchers identified 76 asteroids for which they were able to reliably calculate rotation periods, 19 of them being so-called ultrafast rotators, rotating once every 2.2 hours or more. This figure represents the limit to which a “rubble pile” asteroid, made up of many smaller rocks held loosely by gravity, can spin without collapsing.

The vast majority of asteroids are thought to be piles of rubble, so researchers didn’t expect to find many spinning faster than once every 2.2 hours. The fastest of the high-speed rotators rotates once every 13 minutes or so. In their first round of analyses, the researchers didn’t even look for anything with a spin period shorter than about 5 minutes, Vavilov said during his presentation. “We thought it was crazy that they could turn faster,” he said.

When they went back to look for even faster rotators, they found three that rotated so quickly that they are considered ultra-fast rotators, with periods of about 3.8 minutes, 1.92 minutes and 1.88 minutes, respectively. The fastest, called 2025 MN45, has a diameter of about 710 meters and spins faster than any asteroid larger than 500 m in diameter ever seen before.

Its astonishing speed means this asteroid cannot be a pile of rubble. It must be made of much stronger courage than most space rocks. “2.2 hours is supposed to be the limit for this asteroid, and yet it rotates in less than 2 minutes,” Vavilov said. “Even clay wouldn’t be enough to hold this asteroid together, so it’s probably a large rock or even a solid metal.”

The Vera C. Rubin Observatory is expected to spot many more rotating asteroids during its planned 10-year survey of the southern sky, allowing astronomers to explore the surprising diversity of these strange rocks in space.