Fastest-Rotating Asteroid of Its Size Discovered by Vera C. Rubin Observatory
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A newly discovered asteroid, designated 2025 MN45, is spinning at a record-breaking pace, completing a full rotation in just 1.88 minutes. This makes it the fastest-rotating asteroid larger than 500 meters (0.3 miles) in diameter that scientists have observed to date. The discovery, made by the NSF–DOE Vera C. Rubin Observatory, marks a significant advancement in our ability to study smaller, rapidly rotating objects within the solar system.
A Whirlwind in the Asteroid Belt
The asteroid, measuring 710 meters (0.44 miles) in diameter, resides in the main asteroid belt between Mars and Jupiter. Its astonishing rotational speed challenges existing understanding of asteroid composition and structural integrity. According to a statement released on January 7, 2026, by NOIRLab, 2025 MN45 is a remarkable find.
The discovery was part of a larger haul of 1,900 new solar system objects identified during Rubin’s First Look Event in spring 2025. This event also revealed 19 other super- and ultra-fast-rotating asteroids, highlighting the observatory’s potential for uncovering previously hidden celestial bodies. The peer-reviewed study detailing these findings was published in The Astrophysical Journal Letters on January 7, 2026.
What Keeps This Asteroid From Flying Apart?
The rapid spin of 2025 MN45 presents a puzzle for scientists. Most main-belt asteroids are loosely held together collections of rock and debris. An asteroid spinning this quickly would typically disintegrate due to centrifugal forces. However, 2025 MN45 remains intact, suggesting an exceptionally solid composition.
“For objects in the main asteroid belt, the fast-rotation limit to avoid being fragmented is 2.2 hours; asteroids spinning faster than this must be structurally strong to remain intact,” explained a NOIRLab press release. “The faster an asteroid spins above this limit, and the larger its size, the stronger the material it must be made from.”
Researchers estimate that 2025 MN45 possesses a cohesive strength comparable to solid rock, a surprising finding given that most asteroids are believed to be “rubble pile” asteroids – loosely aggregated collections of smaller fragments. A lead astronomer with the Rubin Observatory’s Solar System Science Collaboration noted that the asteroid’s composition is “somewhat surprising.”
Rubin Observatory’s Expanding View of the Solar System
The Vera C. Rubin Observatory, equipped with the world’s largest digital camera, is revolutionizing our ability to detect and characterize asteroids. The initial observations, conducted over approximately 10 hours across seven nights in April and May 2025, yielded a wealth of data. This data not only led to the discovery of 2025 MN45 and other fast-spinning asteroids but also provided reliable rotation periods for 76 asteroids in total.
Previously, identifying fast-spinning asteroids was challenging, particularly those in the main asteroid belt, due to their distance from Earth. The Rubin Observatory’s powerful camera overcomes this limitation, extending humanity’s reach and enabling the study of a previously inaccessible population of celestial objects. As one researcher explained, Rubin is “successfully allowing us to study a population of relatively small, very-rapidly-rotating main-belt asteroids that hadn’t been reachable before.”
Of the 19 newly discovered fast-spinning asteroids, only one is a near-Earth object (NEO). The remaining objects, including 2025 MN45, reside much further out, between the orbits of Mars and Jupiter. Other notable fast-spinning asteroids identified include 2025 MJ71 (1.9-minute rotation period), 2025 MK41 (3.8-minute rotation period), 2025 MV71 (13-minute rotation period), and 2025 MG56 (16-minute rotation period).
Looking Ahead: The Legacy Survey of Space and Time
Scientists anticipate a surge in discoveries as the Rubin Observatory embarks on its decade-long Legacy Survey of Space and Time. This ambitious project will capture hundreds of high-resolution images of the Southern Hemisphere sky each night, providing an unprecedented dataset for studying the solar system and beyond. The data collected will undoubtedly lead to a deeper understanding of the formation and composition of fast-spinning asteroids.
Watch EarthSky’s Dave Adalian discuss the world’s most powerful camera inside the Vera C. Rubin Telescope with Steven Bellavia: https://www.youtube.com/watch?v=YOUR_YOUTUBE_VIDEO_ID
Ultimately, 2025 MN45 represents a significant step forward in our exploration of the solar system, demonstrating the power of new observational tools and challenging existing theories about asteroid structure and evolution.
Source: Lightcurves, Rotation Periods, and Colors for Vera C. Rubin Observatory’s First Asteroid Discoveries
Via NOIRLab
Read more: See the first Rubin Observatory images here!
