What asteroid, larger than 0.5 km, was reported in January 2026 by the Vera C. Rubin Observatory to have the fastest spin of any known asteroid?

In January 2026, astronomers announced the discovery of asteroid 2025 MN45, a celestial body now recognized for its exceptionally rapid rotation. This particular asteroid, measuring approximately 710 meters (0.4 miles) across, was observed spinning once every 1.88 minutes, or roughly 113 seconds. This makes it the fastest-spinning asteroid known to date that is larger than 0.5 kilometers in diameter. Its discovery was made possible by the cutting-edge capabilities of the Vera C. Rubin Observatory.

The remarkable spin rate of 2025 MN45 offers scientists valuable insights into the asteroid's internal structure. Most asteroids are thought to be "rubble piles," loosely aggregated collections of smaller rocks held together by gravity. These rubble pile asteroids have a "spin barrier" of about 2.2 hours, beyond which they would typically break apart due to centrifugal forces. The fact that 2025 MN45 spins so much faster strongly suggests it is not a rubble pile but rather a solid, cohesive piece of rock with significant internal strength.

The Vera C. Rubin Observatory, located in Chile, is equipped with the Legacy Survey of Space and Time (LSST) Camera, the largest digital camera ever built. This powerful instrument is designed to survey the entire southern sky over a decade, creating an unprecedented time-lapse record of the universe. The discovery of 2025 MN45, along with thousands of other asteroids, was part of the observatory's "First Look" observations in 2025, demonstrating its immense potential for uncovering new and unusual objects within our solar system.

Understanding the characteristics of asteroids like 2025 MN45 is crucial for comprehending the formation and evolution of our solar system. The rotation rates of these ancient space rocks can reveal clues about their collisional histories and the conditions under which they formed billions of years ago. As the Rubin Observatory continues its ambitious survey, astronomers anticipate an avalanche (Review) of new data that will further deepen our knowledge of these fascinating celestial wanderers.