The Vera C. Rubin Observatory has identified 2025 MN45 as the fastest-spinning asteroid discovered to date with a diameter exceeding 500 meters. This finding, derived from data collected during the observatory's early commissioning phase, is part of a broader study that uncovered 19 fast-rotating asteroids, predominantly located in the main asteroid belt. The observations provide new information regarding asteroid composition and challenge existing theories on their structural integrity at high rotational speeds.
Discovery and Characteristics of 2025 MN45
Observations conducted between April 21 and May 5, 2025, during the Vera C. Rubin Observatory’s early commissioning phase, led to the detection of thousands of asteroids, including approximately 1,900 previously uncataloged objects. Among these, asteroid 2025 MN45 was identified as a record-holder.
Key characteristics of 2025 MN45 include:
- Diameter: Approximately 710 meters (0.4 miles or 2,300 feet).
- Rotation Period: Completes one full rotation every 1.88 minutes (113 seconds).
- Location: Resides in the main asteroid belt, situated between Mars and Jupiter.
This combination of size and spin rate establishes 2025 MN45 as the fastest-spinning asteroid over 500 meters in diameter observed to date.
Implications for Asteroid Composition and Spin Theories
Asteroid spin rates offer insights into their formation, internal composition, and evolutionary history. For decades, the prevalent "rubble pile" model posited that most asteroids are loosely bound aggregations of material, held together primarily by gravity. Under this model, main-belt asteroids are generally theorized to fragment if they rotate faster than approximately 2.2 hours. Asteroids exceeding this "spin barrier," particularly larger ones, are therefore inferred to possess significant internal strength, comparable to solid rock.
The rapid rotation of 2025 MN45 suggests it must possess a cohesive strength similar to solid rock to remain intact, contrasting with the typical "rubble pile" composition. This observation, along with 18 other newly identified fast-rotators, challenges the established understanding of asteroid stability, suggesting that some asteroids possess greater strength than previously estimated and necessitates a re-evaluation of asteroid formation and rotation theories. Fast-spinning asteroids may have achieved their rotational speed through collisions or as fragments of larger cosmic impacts.
Broader Findings on Fast-Rotating Asteroids
The study, led by Sarah Greenstreet of NSF NOIRLab and Rubin Observatory’s Solar System Science Collaboration, identified 76 asteroids with reliable rotation periods. Among these:
- Super-fast rotators: 16 objects with rotation periods between 13 minutes and 2.2 hours.
- Ultra-fast rotators: 3 objects with rotation periods under five minutes.
All 19 of these newly identified fast-rotating asteroids exceed 90 meters (100 yards) in length. Notably, all but one of these new fast-rotators reside in the main asteroid belt, or just beyond its outer edge. This finding contrasts with most previously discovered fast-rotating asteroids, which were Near-Earth Objects (NEOs). The presence of multiple fast-spinning asteroids in the main belt, which was previously thought to host slower, more stable asteroids, indicates a potential underestimation of high-density, structurally integrated main-belt asteroids.
Other specific fast-rotating asteroids identified in the study 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). These objects are several hundred meters in diameter.
Rubin Observatory's Role and Future Prospects
The data for this research was collected using the LSST Camera, recognized as the world's largest digital camera, during the observatory's early commissioning phase. This marks the first published peer-reviewed scientific paper utilizing data from the LSST Camera. The Rubin Observatory, jointly funded by the U.S. National Science Foundation and the U.S. Department of Energy’s Office of Science, is located on a Chilean mountaintop and is operated by NSF NOIRLab and SLAC National Accelerator Laboratory. Its advanced light-collecting and measurement capabilities enabled the detection of these objects at greater distances than previously possible for such rapid rotation.
The observatory's primary mission, the 10-year Legacy Survey of Space and Time (LSST), is anticipated to commence shortly. The LSST will conduct regular observations, creating a comprehensive time-lapse record of the Southern Hemisphere night sky. Future LSST observations are projected to uncover additional fast-rotating asteroids, contributing further data to understanding their strengths, compositions, and collisional histories. Researchers anticipate that a larger sample of extremely fast-rotating asteroids will enhance understanding of asteroid physical structures, collisional histories, and the overall formation and evolution of the Solar System, potentially informing future missions like NASA's Lucy spacecraft.
Publication Details
These findings were detailed in a paper titled “Lightcurves, rotation periods, and colors for Vera C. Rubin Observatory’s first asteroid discoveries,” published in The Astrophysical Journal Letters. The research was also presented at the 247th meeting of the American Astronomical Society (AAS) in Phoenix, Arizona.