Artist’s depiction of the asteroid 2025 MN45
NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA/P. Marenfeld
The Vera C. Rubin Observatory in Chile has identified the fastest-spinning large asteroid ever observed. Despite being over half a kilometer in diameter, this asteroid completes a rotation every 1.9 minutes—a speed previously considered unattainable.
Dmitrii Vavilov from the University of Washington in Seattle, along with his team, discovered this asteroid and several other unexpectedly fast rotators during the initial nine nights of Rubin’s observations in late April and early May 2025. Vavilov shared the findings at the Lunar and Planetary Science Conference in Texas on March 17.
During this observation window, the team identified 76 asteroids with calculable rotation periods, 19 of which are considered super-fast rotators, spinning at a rate of once every 2.2 hours or quicker. This rate is the maximum speed a “rubble pile” asteroid—composed of numerous smaller rocks loosely bound by gravity—can achieve without disintegrating.
Most asteroids are believed to be rubble piles, leading researchers to anticipate few would spin faster than every 2.2 hours. The swiftest of these super-fast rotators completes a spin approximately every 13 minutes. Initially, the researchers did not search for objects spinning faster than about 5 minutes per rotation, Vavilov noted in his presentation. “We thought it was unbelievable that they could spin any faster,” he remarked.
Upon revisiting the data, they identified three asteroids spinning at such rapid rates they are classified as ultra-fast rotators, with rotation periods of about 3.8 minutes, 1.92 minutes, and 1.88 minutes, respectively. The fastest among them, named 2025 MN45, measures about 710 meters in diameter and rotates faster than any previously observed asteroid over 500 meters across.
The extraordinary speed of this asteroid suggests it cannot be a rubble pile, as it must be composed of a tougher material than most space rocks. “2.2 hours is the supposed limit for an asteroid like this, yet it completes a rotation in under 2 minutes,” said Vavilov. “Even clay wouldn’t hold this asteroid together, so it’s likely a single large rock or even solid metal.”
The Vera C. Rubin Observatory is expected to detect many more rotating asteroids throughout its planned 10-year survey of the southern sky, providing astronomers with opportunities to study the diverse nature of these peculiar celestial bodies.
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