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Large asteroids have been found spinning so fast they should break apart, suggesting they might be stronger than we thought.

at the University of Washington in Seattle and his colleagues analysed some of the first data collected by the Vera C. Rubin Observatory in Chile, which began a 10-year survey of the sky in June 2026. From a sample of more than 9000 asteroids, they measured the rotation of 260, based on a change in their brightness caused by the spinning asteroids鈥� irregular shapes.

Of these, 66 were deemed to be super-fast rotators, spinning quickly enough to complete a rotation in less than 2.2 hours, a limit at which asteroids should no longer be able to hold themselves together under their own gravity.

Two space rocks in the asteroid belt between Mars and Jupiter were even more unusual ultra-fast rotators. Each was larger than 2 kilometres wide, but completed a full spin once every 5 minutes, something never seen before for such big asteroids.

鈥淥n the scale of billions of years, asteroids of this size should hit each other and reaccumulate,鈥� says Vavilov, forming loose conglomerations of material known as rubble piles that would break apart when rotating rapidly. The high rotation speed suggests that these asteroids aren鈥檛 rubble piles, but instead monolithic objects at least 30 times stronger than clay, says Vavilov.

This probably means our models of how asteroids have smashed together over the 4.6-billion-year history of the solar system aren鈥檛 correct, he says. That might mean these are pristine objects from the early solar system.

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Other fast-spinning asteroids have been spotted before, but nothing as large as these two. Standing on their surface, a person would travel at more than 100 kilometres per hour (over 60 miles per hour), much slower than Earth鈥檚 equatorial rotation of 1670 km/h (1040 mph). But because of the smaller size of the asteroids, it would feel 鈥渓ike a rollercoaster鈥�, says Vavilov, and clinging to the surface would be difficult.

The asteroids might have been spun up by the sun heating their surfaces and giving them torque, known as the YORP effect, but that in itself is uncertain because of their large distance from the sun. 鈥淭hat鈥檚 another mystery,鈥� says Vavilov, who hopes to study the asteroids in more detail in future.