Astronomers analyzing early data from the NSF\u2013DOE Vera C. Rubin Observatory in Chile have identified a record-breaking main-belt asteroid: 2025 MN45<\/strong>. At about 710 meters<\/strong> in diameter, it is the fastest-spinning asteroid of its size class ever found, completing one spin every 1.88 minutes<\/strong>.<\/p>\n\n\n\n That matters because large asteroids typically can\u2019t rotate anywhere near that fast unless they have substantial internal strength. In the main asteroid belt, a common \u201cspin barrier\u201d is about 2.2 hours<\/strong> \u2014 faster than that, loosely bound \u201crubble pile\u201d asteroids should start to break apart.<\/p>\n\n\n\n The simplest explanation is also the most striking: 2025 MN45 is not a rubble pile<\/strong>. Instead, it likely has strong internal cohesion \u2014 closer to solid rock than a gravity-held pile of debris. As astronomer Sarah Greenstreet put it<\/a>:<\/p>\n\n\n\n Clearly, this asteroid must be made of material that has very high strength in order to keep it in one piece.<\/p>\n<\/blockquote>\n\n\n\n At a January 7, 2026 news conference at an American Astronomical Society meeting, Greenstreet emphasized how unusual the discovery is: <\/p>\n\n\n\n It\u2019s unlike anything we\u2019ve been able to see before.<\/p>\n<\/blockquote>\n\n\n\n An asteroid\u2019s spin rate is more than trivia \u2014 it\u2019s a window into its structure and history. A rotation this extreme suggests 2025 MN45 may be a fragment from a catastrophic collision<\/a> long ago, potentially chipped from the denser interior of a larger parent body.<\/p>\n\n\n\n If that\u2019s right, this single \u201csuper-spinner\u201d becomes evidence of the kinds of high-energy impacts that shaped the early Solar System \u2014 and a hint that we may be missing an entire class of unusually strong asteroids simply because they\u2019ve been hard to detect until now.<\/p>\n\n\n\n The record emerged from Rubin\u2019s early commissioning observations in April and May 2025, collected over roughly 10 hours across 7 nights. In that dataset, scientists confirmed about 1,900 never-before-seen asteroids.<\/p>\n\n\n\n From the same observations, the team reported 76 asteroids with reliable rotation periods and identified 19 super- and ultra-fast rotators \u2014 including 2025 MN45.<\/p>\n\n\n\nWhy it doesn\u2019t fly apart<\/h3>\n\n\n\n
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A clue to the Solar System\u2019s violent past<\/h2>\n\n\n\n
Rubin\u2019s early haul<\/h2>\n\n\n\n