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Asteroid 2025 MN45,

The Vera C. Rubin Observatory has discovered the fastest-spinning asteroid ever over 500 meters in size.

Dubbed 2025 MN45, it is a 710 meter long object found in the main asteroid belt between Jupiter and Mars, and it rotates every 1.88 minutes. This discovery, along with that of 18 other fast rotators, represents the first published science results from the Rubin Observatory’s Legacy Survey of Space and Time (LSST), and was released January 7, 2026 in the Astrophysical Journal Letters. The data was taken in April and May 2025, during the commissioning of the Simonyi Survey Telescope’s instruments.

The public got a first look at Rubin’s capabilities back in June 2025, but the real 10-year observing campaign starts in 2026.

In normal circumstances, objects in the asteroid belt tend to spin below 2.2 hours per rotation, in what is known as the spin barrier. Spinning faster than this usually results in an asteroid breaking up into smaller pieces, or splitting into a binary object.

The spin barrier is determined by several factors, including the ratio of icy to rocky material within an object, its size, and whether the asteroid is a single solid chunk or a rubble pile of tiny pieces. Astronomers believe ‘rubble piles’ are the most common type of asteroid, but with its fast spin time, 2025 MN45 is definitively not one.