Giant asteroids spinning too fast should be impossible

When asteroids break the laws of physics

Astronomers have discovered something that shouldn’t exist: massive asteroids spinning so rapidly they should tear themselves apart. Dmitrii Vavilov at the University of Washington and his team analyzed data from the Vera C. Rubin Observatory in Chile, which began scanning the sky in June 2026. Among more than 9,000 asteroids observed, they identified 260 whose rotation could be measured through brightness variations caused by their irregular shapes.

The findings are startling. Sixty-six asteroids were classified as super-fast rotators, completing a full rotation in under 2.2 hours, the theoretical limit where gravity can no longer hold an object together. But two asteroids took the mystery even further.

These two space rocks, each wider than 2 kilometers, completed a full spin every 5 minutes. For context, nothing this large has ever been observed rotating at such speeds. If you stood on one of these asteroids’ equators, you’d be traveling at over 100 kilometers per hour without any visible motion, creating what Vavilov describes as a “rollercoaster” sensation. Clinging to the surface would be nearly impossible.

Rethinking asteroid structure

The conventional model of asteroid formation has always held that these space rocks should be rubble piles, loose conglomerations of material held together only by gravity. Over billions of years, collisions would scatter them and they’d reaccumulate into these fragile structures.

But these ultra-fast rotators contradict that model entirely. According to Vavilov’s analysis, these asteroids must be monolithic objects, solid chunks of rock at least 30 times stronger than clay. This discovery suggests our understanding of how asteroids collide and reform throughout solar system history may be fundamentally flawed.

If these asteroids aren’t rubble piles, what are they? Vavilov proposes they might be pristine objects from the early solar system, essentially time capsules from 4.6 billion years ago. This would rewrite what we know about planetary formation and the composition of our cosmic neighborhood.

Fast-spinning asteroids have been spotted before, but always at smaller scales. This discovery breaks that pattern entirely. Larger asteroids should be too massive to spin this quickly without fragmenting into pieces. Yet here they are, defying expectations.

The mystery of acceleration

One critical question remains unanswered: how did these asteroids get spinning so fast in the first place? The leading hypothesis involves the YORP effect, where the sun’s heat causes asteroids to gradually spin up over time. However, Vavilov notes this mechanism faces a major obstacle with these distant space rocks.

“That’s another mystery,” Vavilov says, highlighting just how much remains uncertain about these objects. Their distance from the sun makes the YORP effect an unlikely culprit, yet no better explanation currently exists. This gap in our understanding drives home how much astronomy still has to discover about the cosmos.

The Vera C. Rubin Observatory’s 10-year survey has only just begun, and already it’s upending assumptions that researchers thought were settled. Future observations may reveal whether these two ultra-fast rotators are outliers or the first evidence of an entire class of asteroids we’ve fundamentally misunderstood.

Vavilov and his colleagues plan to study these asteroids in more detail, hoping to unlock their secrets. Each observation could either confirm existing models or force another complete rethinking of how our solar system came to be.

Based on reporting from New Scientist

What else might we discover about asteroids that challenges everything we thought we knew?