Leveraging data transmitted from NASA’s Juno spacecraft, celestial researchers have achieved the most precise determinations of Jupiter’s dimensions in fifty years, revealing that the Solar System’s colossus is more slender and less oblate than previously conceptualized.
Hubble’s photographic depiction of Jupiter showcases the dynamic and ever-shifting panorama of its tempestuous atmosphere. Credit for the image: NASA / ESA / Hubble / Amy Simon, NASA’s Goddard Space Flight Center / Michael H. Wong, University of California, Berkeley / Joseph DePasquale, STScI.
“Our prior comprehension of Jupiter’s form was derived by investigators from a mere six measurements conducted nearly five decades ago by NASA’s Voyager and Pioneer missions, which facilitated radio transmissions from their onboard instruments to Earth,” stated Dr. Eli Galanti, a scientist affiliated with the Weizmann Institute of Science.
“While those pioneering missions laid a crucial groundwork, we have now been afforded a singular occasion to lead the comprehensive analysis of an extensive dataset comprising up to 26 novel measurements acquired by NASA’s Juno spacecraft.”
“Simply by ascertaining the distance to Jupiter and observing its rotational velocity, it becomes feasible to deduce its dimensions and overall configuration,” explained Professor Yohai Kaspi from the Weizmann Institute of Science.
“However, achieving measurements of exceptional accuracy necessitates the deployment of more sophisticated methodologies.”
“Juno’s orbital trajectories that pass behind Jupiter present invaluable opportunities for novel scientific investigations,” commented Dr. Scott Bolton, the principal investigator for Juno and a researcher at the Southwest Research Institute.
“When the spacecraft traverses behind the planet, its radio communication signal experiences obstruction and refraction by Jupiter’s enveloping atmosphere. This phenomenon facilitates a highly precise quantification of Jupiter’s physical size.”
“By meticulously tracking the deflection of radio signals as they propagate through Jupiter’s atmosphere, we were empowered to translate this observed behavior into detailed cartographic representations of Jupiter’s thermal profile and density distribution, thereby yielding the most lucid depiction to date of the giant planet’s scale and morphology,” elucidated Maria Smirnova, a doctoral candidate at the Weizmann Institute of Science.
The research team determined Jupiter’s polar radius to be 66,842 kilometers, its equatorial radius to be 71,488 kilometers, and its mean radius to be 69,886 kilometers—each value falling below prior estimates by margins of 12, 4, and 8 kilometers, respectively.
“Educational texts will likely require revision. While Jupiter’s intrinsic size remains immutable, the methodologies we employ for its measurement have undergone significant advancement,” Professor Kaspi remarked.
“These minor variations of a few kilometers are of considerable consequence. Even a slight adjustment in the radius allows our internal models of Jupiter to reconcile both gravitational data and atmospheric observations with significantly greater fidelity,” asserted Dr. Galanti.
“We occupied a distinctive vantage point, enabling us to leverage our cutting-edge models of Jupiter’s internal density structure, thereby demonstrating how this refined geometrical understanding serves to effectively bridge the disparities between theoretical models and empirical observations,” stated Maayan Ziv, a Ph.D. candidate at the Weizmann Institute of Science.
Previous measurement endeavors failed to adequately account for Jupiter’s formidable atmospheric currents. By integrating these dynamic factors into their computational frameworks, the scientists have successfully resolved long-standing discrepancies that had persisted for decades.
“It presents a considerable challenge to ascertain the processes occurring beneath Jupiter’s cloud layers; however, the radio telemetry data furnish us with an insightful aperture into the profound depths of Jupiter’s zonal winds and its powerful cyclonic systems,” observed Professor Kaspi.
The findings stemming from this investigation are published in the esteemed journal Nature Astronomy.
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E. Galanti et al. 2026. The size and shape of Jupiter. Nat Astron 10, 493-501; doi: 10.1038/s41550-026-02777-x
