Fastest-Rotating Rock Known, Larger Than 6 Football Fields, Is Rubin Observatory’s First Discovery
In A Nutshell
- Record breaker: Asteroid MN45 spins once every 1.88 minutes (about 765 times per day) making it the fastest-rotating large asteroid known to science
- Defying physics: Scientists found 19 asteroids spinning faster than the theoretical “spin barrier” of 2.2 hours, with three completing rotations in under 5 minutes
- Surprisingly strong: These ultrafast rotators must be as strong as solid rock to avoid flying apart, challenging the assumption that most asteroids are loose rubble piles
- More to come: The discoveries came from just nine nights of observations during telescope commissioning; the full 10-year survey could find thousands more extreme rotators
Scientists using a powerful new sky survey telescope have discovered something extraordinary: an asteroid larger than six football fields spinning like a top at breakneck speed, completing a full rotation in less than two minutes. The discovery brings about new questions about what holds asteroids together and how fast they can spin without flying apart.
Asteroid 2025 MN45, discovered by the Vera C. Rubin Observatory in Chile, is now the fastest-rotating large asteroid known so far. At roughly 0.71 kilometers across (about 2,300 feet), this space rock whips around completely every 1.88 minutes. That’s about 765 full rotations every single day.
“These are the first science results derived from the 2103 asteroid discoveries…” made during the telescope’s commissioning phase, researchers report in The Astrophysical Journal Letters. Between April 21 and May 5, 2025, the observatory captured nearly 340,000 asteroid detections across nine nights, providing an unprecedented look at how asteroids move and rotate.
But MN45 wasn’t alone. The team identified two more “ultrafast rotators” with periods under five minutes: asteroid 2025 MK41 spinning every 3.78 minutes, and near-Earth asteroid 2025 MJ71 completing rotations in just 1.92 minutes. Together with two additional super-rapid rotators (MV71 at 13 minutes and MG56 at 16 minutes), these five asteroids are rewriting the rules.
Breaking the Spin Barrier
Astronomers have long known about a theoretical “spin barrier” for asteroids. Objects larger than about 150 meters across shouldn’t be able to rotate faster than once every 2.2 hours without tearing themselves apart. The centrifugal force at higher speeds should overcome the asteroid’s self-gravity, causing it to fragment or shed material into space.
Yet the Rubin Observatory found 19 asteroids spinning faster than this barrier, with the three ultrafast rotators obliterating it entirely. For these asteroids to survive at such extreme rotation rates, they must be made of surprisingly strong material, far more cohesive than the loose rubble piles scientists once thought characterized most asteroids.
Based on their calculations, the researchers estimate that MN45 must be incredibly strong to avoid flying apart, likely as strong as a solid chunk of rock rather than a loose pile of gravel. The other ultrafast spinners would need similar strength to stay in one piece. These asteroids either have real internal strength binding them together or are solid pieces of rock, not the loose rubble piles scientists once expected.
“With rotation periods of less than five minutes, MN45, MJ71, and MK41 belong in a category all their own,” the research team explains. Previously, only a couple of near-Earth asteroids had been confirmed spinning this rapidly. Now three more have joined their ranks, and most surprisingly, two are main-belt asteroids, which are space rocks orbiting between Mars and Jupiter, far from Earth.
A Treasure Trove of Rotation Data
The discoveries came from the Rubin First Look dataset, a preliminary glimpse at what the telescope will accomplish once it begins its Legacy Survey of Space and Time in early 2026. During commissioning tests, the observatory imaged a 24-square-degree region of sky near the Virgo galaxy cluster, returning to the same area repeatedly over nine nights.
This observing pattern was ideal for detecting fast rotators. With over 60 images taken on most nights within just a few hours, researchers could catch asteroids as they brightened and dimmed with each rotation. For asteroids spinning every few minutes, dozens of complete rotations could be observed in a single night.
Sarah Greenstreet of the University of Washington and NOIRLab led the analysis, working with an international team to track brightness changes (called lightcurves) for roughly 2,000 objects from the dataset. They found reliable rotation periods for 76 asteroids ranging from 1.9 minutes to over 21 hours, with the majority being main-belt asteroids too dim for most surveys to study.
A close-up on two galactic members of the Virgo Cluster as imaged by NSF–DOE Vera C. Rubin Observatory. During its observations Rubin captured a plethora of asteroids zipping across this portion of the night sky, indicated by the tri-colored streaks scattered throughout this image. (Credit:
RubinObs / NOIRLab / SLAC / NSF / DOE / AURA)
How Did They Get Spinning So Fast?
The existence of these ultrafast rotators raises a puzzling question: How did they achieve such extreme rotation rates? There are several potential explanations, though none is certain.
One possibility is recent collisions. When two asteroids smash together, the impact can set fragments spinning at high speeds. If MN45 formed from such a collision relatively recently in geologic terms, it might not have had time to slow down yet.
Another mechanism is the YORP effect (named after four scientists who studied it). Over millions of years, sunlight hitting an irregularly shaped asteroid can create tiny torques that gradually speed up or slow down its rotation. For small asteroids, this effect can be surprisingly powerful, potentially spinning them up to destructive speeds or even splitting them into binary systems.
The ultrafast rotators might also simply be made of unusually strong material. If they’re monolithic chunks of solid rock rather than rubble piles, they could withstand centrifugal forces that would tear apart weaker asteroids. Their survival at these speeds offers a rare window into asteroid internal structure, something difficult to determine through observations alone.
Elongated Shapes
The brightness tracking also revealed that many asteroids are far from spherical. As an asteroid rotates, its brightness varies depending on how much surface area faces the Sun. Highly elongated objects show bigger brightness swings, while nearly spherical asteroids stay about the same brightness.
Five asteroids showed dramatic brightness changes, suggesting they’re shaped more like potatoes or footballs than spheres—roughly twice as long as they are wide. Among the ultrafast rotators, some are moderately elongated despite their breakneck rotation speeds.
Several asteroids showed irregular brightness patterns, suggesting either lumpy, irregular shapes or possibly even binary systems (two asteroids orbiting each other.) About 15 percent of all asteroids are binaries, so some objects in this sample are likely paired rocks rather than single bodies.
What’s Next for Rubin
The Vera C. Rubin Observatory marks a massive leap forward in sky survey capability. Its 8.4-meter mirror and 3.2-gigapixel camera capture a field of view of about 9.6 square degrees — roughly equivalent to 40 full moons — in a single 30-second exposure.
When the decade-long Legacy Survey of Space and Time begins in early 2026, the observatory will repeatedly image the southern sky, revisiting the same areas every few nights. Over 10 years, it should discover and track up to 5 million small bodies in the solar system from near-Earth asteroids to distant objects beyond Neptune’s orbit.
The current findings suggest these ultrafast rotators are more common than previously thought. In this sample of 2,000 objects, the team found three spinning faster than 5 minutes, about 0.15 percent. If that fraction holds across the larger asteroid population, thousands of these extreme rotators await discovery.
Each new detection will help scientists understand asteroid internal structure, collision physics, and the violent history of the asteroid belt over the past 4.6 billion years.
Asteroid MN45 holds the record as the fastest-spinning large asteroid known to science. But given the surprises already emerging from Rubin Observatory’s first observations, that record may not stand for long.
Paper Summary
Limitations: The study notes several important limitations. The observations span only 12 days or less per object, limiting the ability to fully constrain asteroid shapes and spin axis orientations. The phase angle coverage is relatively narrow (about 10 to 20 degrees), restricting shape modeling precision. The determination of ultrafast rotation periods, while validated through multiple independent methods and scrutinized across individual nights, remains challenging at the edge of the data’s temporal sampling capabilities. Some of the asteroids may show signs of cometary activity, which could affect rotation period measurements but was not systematically investigated as the team lacked access to the actual images through the Minor Planet Center query. The reliability threshold required at least 30 observations in two photometric bands with modeled amplitudes above 0.1 magnitude, meaning many objects in the full 2,103-object dataset could not have rotation periods reliably determined. Finally, while three-color photometry (g, r, i bands) enables asteroid type classification between C-type and S-type objects, the lack of z-band observations prevents identification of V-type asteroids.
Funding and Disclosures: This material is based on work supported by the National Science Foundation through Cooperative Agreements AST-1258333, AST-2241526, AST-1202910, and AST-2211468 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under contract DE-AC02-76SF00515 with SLAC National Accelerator Laboratory managed by Stanford University. Additional Rubin Observatory funding comes from private donations, grants to universities, and in-kind support from institutional members. The work of Sarah Greenstreet is supported by NOIRLab, managed by AURA under a cooperative agreement with the National Science Foundation. The research is supported by NSF grants 2307569 and 2307570, and partially funded by a generous gift from Charles Simonyi to the NSF Division of Astronomical Sciences. The work is also supported by NASA Solar System Workings grant 80NSSC22K0978. Support from the DiRAC Institute at the University of Washington is acknowledged, funded through gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences, Janet and Lloyd Frink, and the Washington Research Foundation. The work of Alec Koumjian and Joachim Moeyens is supported by the Asteroid Institute, a program of the B612 Foundation, through multiple leadership gifts. Valerio Carruba is grateful to the Brazilian National Research Council (CNPq, grant 304168/2021-1) and the São Paulo Research Foundation (FAPESP, grant 2025/01469-0).
Publication Details
Sarah Greenstreet et al. (2026). “Lightcurves, Rotation Periods, and Colors for Vera C. Rubin Observatory’s First Asteroid Discoveries.” The Astrophysical Journal Letters, Volume 996, Number 2, L33. DOI: 10.3847/2041-8213/ae2a30. The research team includes authors from multiple institutions: Sarah Greenstreet (University of Washington and NOIRLab), Zhuofu (Chester) Li, Dmitrii E. Vavilov, Devanshi Singh, Mario Jurić (University of Washington), Željko Ivezić (University of Washington), Siegfried Eggl (University of Illinois at Urbana-Champaign), Alec Koumjian and Joachim Moeyens (Asteroid Institute, B612 Foundation), and Valerio Carruba (São Paulo State University, Brazil). Published January 7, 2026.
By StudyFinds Analysis • Reviewed by Steve Fink