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Artist\u2019s depiction of the asteroid 2025 MN45<\/p>\n
NSF\u2013DOE Vera C. Rubin Observatory\/NOIRLab\/SLAC\u200b\/AURA\/P. Marenfeld<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
The Vera C. Rubin Observatory in Chile has spotted the fastest-rotating large asteroid ever seen. Despite measuring more than half a kilometre across, this asteroid spins about once every 1.9 minutes \u2013 a speed once thought to be impossible.<\/p>\n
Dmitrii Vavilov at the University of Washington in Seattle and his colleagues found this asteroid, along with several other surprisingly speedy rotators, in the data from Rubin\u2019s first nine nights of observations in late April and early May 2025. Vavilov presented the results at the Lunar and Planetary Science Conference in Texas on 17 March.<\/p>\n
<\/p>\n In that observation period, the researchers identified 76 asteroids for which they could reliably calculate rotational periods, with 19 of those being so-called super-fast rotators, spinning once every 2.2 hours or faster. That figure is the limit of how fast a \u201crubble pile\u201d asteroid, made up of many smaller rocks loosely held together by gravity, can spin without falling apart.<\/p>\n The vast majority of asteroids are thought to be rubble piles, so the researchers didn\u2019t expect to find many rotating faster than once every 2.2 hours. The fastest of the super-fast rotators spins once every 13 minutes or so. In their first set of analyses, the researchers didn\u2019t even look for anything with a spin period of less than about 5 minutes, Vavilov said during his presentation. \u201cWe thought that was crazy that they could rotate any faster,\u201d he said.<\/p>\n When they went back and looked for even faster rotators, they found three spinning so rapidly that they are considered ultra-fast rotators, with periods of about 3.8 minutes, 1.92 minutes and 1.88 minutes, respectively. The fastest, called 2025 MN45, has a diameter of about 710 metres and spins faster than any asteroid more than 500m across ever seen before.<\/p>\n Its astonishing speed means this asteroid can\u2019t possibly be a rubble pile. It must be made of much stronger mettle than most space rocks. \u201c2.2 hours is supposed to be the limit for this asteroid, and yet it\u2019s rotating in less than 2 minutes,\u201d said Vavilov. \u201cEven clay would not be enough to hold this asteroid together, so it\u2019s probably one big rock or even solid metal.\u201d<\/p>\n The Vera C. Rubin Observatory is expected to spot many more rotating asteroids over the course of its planned 10-year survey of the southern sky, enabling astronomers to explore the surprising diversity of these strange boulders in space.<\/p>\n Topics:<\/p>\n<\/section><\/div>\n