NASA’s Vera C. Rubin Observatory is shaking up our understanding of asteroids. Long before its main survey, the telescope spotted a giant asteroid named 2025 MN45. It’s an impressive 710 meters (2,330 feet) wide and spins every 1.88 minutes. This is astounding because scientists believed that any asteroid over 150 meters would break apart if it spun faster than 2.2 hours.
But that’s not all. They discovered 18 other asteroids spinning at seemingly impossible speeds. These findings raise important questions about what we think we know regarding asteroid strength. According to astronomer Sarah Greenstreet, these fast-spinning giants suggest that our assumptions about asteroid construction and evolution need to change.
Asteroids are minor planets that offer clues about our Solar System’s early days. However, they’re hard to study. They’re small, often dark, and move quickly. That makes gathering details about their size and rotation quite a challenge. Rubin’s mission aims to create the most comprehensive catalog of asteroids we’ve ever had.
Traditionally, scientists considered asteroids to be “rubble piles” held together by weak gravity. Imagine riding a Gravitron; if you’re packed tightly, you stay together, but if you’re too loose, you’ll fly apart. This concept led to the belief that larger asteroids would spin slowly to avoid breaking apart.
But recent observations from Rubin changed this view. Between late April and early May 2025, the telescope gathered data on around 340,000 asteroids, focusing on their rotation speeds. They found a shocking 19 of them had spin rates below the expected threshold, revealing a hidden strength in these celestial bodies.
While most fast rotators were expected to be found near Earth, it turns out the Main Belt is home to many more. Of the new speedy spins, only one was a near-Earth object.
The fact that so many Main Belt asteroids—especially the large ones—exceeded the spin barrier suggests that many could have a denser and more robust structure than we thought. Greenstreet highlights that 2025 MN45 must be made from very strong material to withstand its rapid rotation, similar to solid rock. This may imply that some asteroids are remnants of violent collisions from the early Solar System, preserving characteristics that most others lost.
These findings not only excite astronomers but also pave the way for future research. Upcoming missions, like NASA’s Lucy spacecraft, will explore these asteroids more closely. The researchers believe that studying a wider range of fast-rotating asteroids could unlock new insights into their structure and the history of our Solar System.
Published in The Astrophysical Journal Letters, these discoveries signal a shift in our understanding of the cosmos. With new insights, the world might be on the brink of exciting revelations about the very building blocks of our universe.
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