Asteroid 491384 Completes a Rotation in 4.18 Minutes Despite Its Size
Astronomers have identified asteroid 491384 as the quickest rotating known space rock, completing a turn in about 4.18 minutes. It is roughly 2.5 kilometers across, which is unexpectedly large for such a rapid spin. The team used the Vera C. Rubin Observatory's LSST camera and found several other ultra-fast rotators, suggesting some asteroids may be held together by internal strength rather than gravity alone.
Astronomers used the Rubin Observatory's LSST camera, a 3,200-megapixel instrument built to map the southern sky and create a time-lapse view. In a catalog of more than 9,400 asteroids, they identified 1,221 candidates, then 66 super-fast rotators exceeding the classical 2.2-hour limit and five ultra-fast rotators turning in under five minutes.
Asteroid 491384, about 2.5 km wide, spins once in roughly 4.18 minutes. Another object, 566130, has a 5.34-minute period and a 2 km diameter. Both appear too large to remain intact under rapid rotation unless they possess substantial internal cohesion, the researchers suggest.
This result may refine how astronomers model asteroid strength and rotation, affecting researchers who study small bodies and teams planning sky surveys. It could also shape future follow-up observations and interpretations of asteroid populations, though it does not by itself imply an immediate change in public safety or policy.