Rubin Observatory spots fastest-spinning asteroid over 500 meters

The Vera C. Rubin Observatory identified asteroid 2025 MN45, a 710-meter object in the main asteroid belt that rotates every 1.88 minutes, and reported the finding as part of the first published science results from its LSST commissioning data.

Rubin Observatory has reported a very fast-spinning asteroid found during instrument commissioning. The object, named 2025 MN45, is about 710 meters long and lies in the main asteroid belt between Mars and Jupiter. It completes one rotation in 1.88 minutes, faster than the typical spin barrier of about 2.2 minutes. The result was released January 7, 2026 as part of the first published science results from the LSST commissioning data. Key facts: - 2025 MN45 measures about 710 meters and rotates every 1.88 minutes. - The asteroid was found in the main asteroid belt; many belt objects spin below the roughly 2.2-minute spin barrier. - The published paper describes 19 fast rotators in total, with 18 in the main belt and one outside it. - Study lead Sarah Greenstreet reported that 2025 MN45 would need cohesive strength similar to solid rock to remain intact at its spin rate, indicating it is not a rubble pile. - Data were taken in April–May 2025 during Rubin's commissioning; Rubin's full 10-year LSST survey begins in 2026. Summary: This discovery illustrates Rubin Observatory's capability to detect rapidly changing objects at greater distances than before and adds new observational data on asteroid spin and internal strength. The paper reporting 19 fast rotators was published January 7, 2026, and the full LSST survey will begin in 2026. Additional survey observations are expected to produce more detections and help refine understanding of asteroid structure and populations.