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4h ago

Rubin Observatory Finds Record Fast-Spinning, Half-Mile-Wide Asteroid in First Test Data

The asteroid’s 113-second rotation suggests cohesive, rock-like strength rather than a loose rubble pile.

This artist’s illustration depicts 2025 MN45 — the fastest-rotating asteroid with a diameter over 500 meters that scientists have ever found. The asteroid is shown surrounded by many other asteroids, depicting its location within the main asteroid belt. The Sun and Jupiter are shown in the distance. 2025 MN45 is 710 meters (0.44 miles) in diameter, and it completes a full rotation every 1.88 minutes. The discovery was made using data from NSF–DOE Vera C. Rubin Observatory, jointly funded by the U.S. National Science Foundation and the U.S. Department of Energy's Office of Science.
This lightcurve shows how the asteroid’s brightness (x-axis) changes as it rotates (y-axis). Analyzing the curve allowed the team to calculate the asteroid's rotation speed, which sets a new record among asteroids of its size.

Overview

  • Designated 2025 MN45, the main-belt object measures about 710 meters across and completes a full spin in roughly 1.88 minutes, the fastest known for asteroids larger than 500 meters.
  • The finding comes from early commissioning images taken over seven nights in April and May 2025 with Rubin’s 3,200‑megapixel LSST Camera, which can capture a new exposure about every 40 seconds.
  • Researchers identified about 1,900 previously unknown asteroids in the dataset, including 19 super‑ and ultra‑fast rotators longer than a football field, with all but one located in the main belt.
  • The results appear in The Astrophysical Journal Letters as the first peer‑reviewed paper using LSST Camera data and were presented at the American Astronomical Society meeting in Phoenix.
  • Scientists note the object poses no imminent impact threat to Earth, and the full 10‑year Legacy Survey of Space and Time expected to begin in the coming months should yield many more such discoveries.