Rubin Observatory finds two large asteroids that spin in a matter of minutes
A roughly 2.5-kilometer rock completes one rotation in just over four minutes, a record for its size, according to a study that has not yet been peer-reviewed.
Archive image · Photo: NOIRLab/NSF/AURA/C. Corco / Wikimedia Commons, CC BY 4.0 (cropped and resized)
Data from the new Vera C. Rubin Observatory in Chile have revealed two unusually fast-spinning asteroids in the main belt between Mars and Jupiter. Asteroid 491384 is about 2.53 kilometers across and rotates once in about 4.18 minutes. A team including Dmitrii Vavilov of the University of Washington in Seattle says that makes it the largest known asteroid with a rotation period under five minutes. The second, 566130, is about 1.99 kilometers wide and spins once every 5.34 minutes.
Asteroids larger than about 150 meters typically need at least 2.2 hours per rotation. Loose rubble piles held together only by gravity would fly apart at faster speeds. The team therefore calculates an internal strength of about 2.3 and 0.9 megapascals respectively, meaning the material must hold together unusually firmly.
The researchers analyzed 9,417 asteroids, each with at least 80 brightness measurements taken between April 2025 and January 2026. The study has so far appeared only as an arXiv preprint and has not been peer-reviewed. Diameters were derived from brightness rather than measured directly, and the authors recommend targeted follow-up observations.