Vera C. Rubin Observatory astronomers report 710-metre asteroid rotating every 1.88 minutes
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Astronomers at the Vera C. Rubin Observatory have identified asteroid 2025 MN45, estimated at 710 metres in diameter, completing a full rotation every 1.88 minutes. The rotation period, reported on 7 January 2026 in The Astrophysical Journal Letters, is roughly 70 times faster than the 2.2-hour spin barrier for loose main-belt asteroids. Researchers estimate the object needs about 9 megapascals of cohesion to remain intact.
Key Facts
- 2025 MN45 has an estimated diameter of 710 metres and was found in commissioning data from the NSF-DOE Vera C. Rubin Observatory in Chile.
- The asteroid rotates once every 1.88 minutes (0.031 hours), about 70 times shorter than the 2.2-hour spin barrier for near-cohesionless main-belt asteroids larger than 150 metres.
- Keeping 2025 MN45 intact at that spin requires about 9 megapascals of cohesion, comparable to strong clay or rock.
- The team used 517 observations across 12 days, and the same period appeared across nights, colour filters, and two independent techniques.
- Sarah Greenstreet and colleagues published the findings in The Astrophysical Journal Letters on 7 January 2026.
Rotation Period
2025 MN45 was identified in commissioning data from the NSF-DOE Vera C. Rubin Observatory in Chile. Sarah Greenstreet and colleagues reported the measurement in The Astrophysical Journal Letters on 7 January 2026. The asteroid completes a full turn every 1.88 minutes, or 0.031 hours, roughly 70 times faster than the 2.2-hour spin barrier for near-cohesionless main-belt asteroids larger than about 150 metres. The team had 517 observations across 12 days, and the same period appeared when the data were separated by night and colour filter and recovered by two independent techniques.
Cohesion Estimate
Using the nominal diameter and 112.8-second period, the asteroid’s equator travels at roughly 71 kilometres per hour. An established model, assuming a sphere with bulk density of 1,700 kilograms per cubic metre, produced a cohesion estimate of about 9 megapascals. That value is comparable to strong clay or rock, but it rests on assumed albedo, density and shape rather than a direct material sample. The calculation indicates that self-gravity cannot explain how an object with the nominal size and measured period stays together.
Rubble-Pile Barrier
Many asteroids are rubble piles held together largely by weak self-gravity after collisions. For nearly cohesionless main-belt asteroids larger than about 150 metres, observations show a spin barrier near 2.2 hours. Below that period, rotation makes a typical rubble pile deform, shed stones or break apart. 2025 MN45’s reported period is about one-seventieth as long, so the object fits the rubble-pile picture poorly.
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Vera C. Rubin Observatory astronomers report 710-metre asteroid rotating every 1.88 minutes
