The NSF-DOE Vera C. Rubin Observatory’s First Look media event that took place on June 23, 2025 in which the first LSST Camera commissioning images were released, included the announcement of its first asteroid discoveries – 2,103 discoveries in all. The roughly 340,000 individual detections in which the 2,103 discoveries were made span 9 nights between April 21 and May 5, 2025. With a faint magnitude range (~23-25 mag) and dense temporal sampling under an irregular, commissioning‑driven cadence, the Rubin First Look observations provide an ideal testbed for determining asteroid rotation periods, including the detection of rapid rotation. In a paper, currently in press in The Astrophysical Journal Letters, NSF NOIRLab Assistant Astronomer and UW Astronomy Affiliate Assistant Professor Sarah Greenstreet, UW Astronomy graduate student Chester Li, UW Astronomy postdoctoral scholar Dmitrii Vavilov and their colleagues present light curves, rotation periods, and colors for the first asteroid discoveries made with the NSF-DOE Vera C. Rubin Observatory.
The paper includes modeled light curves and derived rotation periods and colors for the 2,103 objects, finding 75 asteroids with reliable, robust rotation periods spanning < 2 minutes to > 21 hours; each of the 75 asteroids in the data set reside in the Solar System’s main asteroid belt between the orbits of Mars and Jupiter. Notably, they find 18 super-fast rotators with periods shorter than the 2.2-hr spin barrier; the spin barrier is the maximum rotation rate an object can sustain before the centrifugal force overcomes self-gravity, potentially leading to structural fragmentation of the asteroid or the formation of a binary asteroid. Surprisingly, they additionally find that Rubin-discovered main-belt asteroid (MBA) 2025 MN45 is now the fastest rotating known asteroid with a diameter larger than 0.5 km (longer than the length of 5 football fields), rotating once every 1.9 min! Along with Rubin-discovered near-Earth object (NEO) 2025 MJ71 (3.7 min) and MBAs 2025 MK41 (3.8 min), 2025 MV71 (13 min), and 2025 MG56 (16 min), these five ultra-fast rotators now join a couple of previously-known near-Earth asteroids as the fastest spinning sub-km asteroids known.
As this study demonstrates, even in early commissioning, Rubin is successfully probing the previously sparsely sampled population of large-sized asteroids that reside at greater distances than other astronomical surveys have been able to observe spinning at these very fast rotation speeds. Although this data set consists of observations taken at a different cadence, subject to the requirements of Rubin’s commissioning period, than will be followed during Rubin’s Legacy Survey of Space and Time (LSST), expected to start later this year, with millions of asteroid discoveries expected from the survey in the coming years, the findings of this study are just the beginning of the exciting science the Rubin Observatory will unlock and the astronomers at UW Astronomy’s DiRAC Institute are poised to lead.
Sarah Greenstreet 
Dmitrii Vavilov 
Chester Li
About Sarah Greenstreet
Sarah Greenstreet is a tenure-track assistant astronomer at the NSF National Optical-Infrared Astronomy Research Laboratory (NOIRLab) and an affiliate assistant professor in the University of Washington’s Department of Astronomy. She is also a member of the Rubin Observatory Community Science Team and has served as the Lead for the Rubin Observatory Solar System Science Collaboration’s Near-Earth Objects and Interstellar Objects Working Group for the past seven years. Prof. Greenstreet’s research program broadly focuses on orbital dynamics, characterization, and impacts of small bodies across the Solar System, with a particular focus on the rarest and most unusual asteroids. To learn more about her research, please visit her website: www.sarahgreenstreet.com.
About Dmitrii Vavilov
Dmitrii Vavilov is a postdoctoral researcher at the University of Washington and a former Marie Skłodowska-Curie Fellow at the Paris Observatory. He studied astronomy at St. Petersburg State University and earned his Ph.D. in celestial mechanics from the Institute of Applied Astronomy of the Russian Academy of Sciences. His research focuses on the dynamics and physical properties of small Solar System bodies (like asteroids and comets) from their dynamical evolution to shape transformations. He developed the Partial Banana Mapping (PBM) method, an efficient approach for modeling orbital uncertainties to predict Earth-impact probabilities, precoveries, and follow-up observations. He is a member of the International Astronomical Union, and asteroid (34583) DmitriiVavilov has been named in his honor.
About Chester Li
Zhuofu (Chester) Li is a Ph.D. student studying Astrophysics, Statistics, and Data Science at the University of Washington. His research integrates data science, astrophysics, and machine learning to explore the mysteries of the Universe. Chester’s recent work includes estimating rotation periods for Jupiter Trojans using Zwicky Transient Facility lightcurves, identifying temporary Jovian co-orbitals through large-scale N-body simulations, and applying simulation-based inference with normalizing flows to constrain dark matter using stellar streams. He is also the founder of the UW Data Science Society, where he builds interdisciplinary collaborations between astronomy, statistics, and computer science.