Astronomers Find 710-Meter Asteroid Spinning Every 1.88 Minutes, Defying the 2.2-Hour Rubble-Pile Limit
Updated
Updated · spacedaily.com · Aug 21
Astronomers Find 710-Meter Asteroid Spinning Every 1.88 Minutes, Defying the 2.2-Hour Rubble-Pile Limit
1 articles · Updated · spacedaily.com · Aug 21
Summary
2025 MN45, a main-belt asteroid estimated at 710 meters wide, completes one rotation in 112.8 seconds—about 70 times faster than the 2.2-hour spin limit where a loose body that size should start breaking apart.
517 observations collected over 12 days from Vera C. Rubin Observatory commissioning data produced the same 0.031-hour signal across separate nights and color filters, with two independent methods recovering the period.
A model using the nominal size and a density of 1,700 kilograms per cubic meter says the asteroid needs roughly 9 megapascals of cohesion to stay intact, pointing to rock-like strength rather than a typical rubble-pile structure.
The size and strength remain inferred rather than directly measured because diameter depends on assumed reflectivity, but the study's central result is that self-gravity alone cannot explain the reported spin.
Rubin's First Look data yielded reliable periods for 76 asteroids, including 19 faster than the 2.2-hour barrier, suggesting the observatory's full survey could uncover many more unusually cohesive fast rotators.