Jupiter is slightly smaller and flatter, Juno data shows

Radio occultation data from 13 Juno flybys indicate Jupiter's equatorial width is about 8 kilometers less and its polar flattening about 24 kilometers greater than earlier estimates; the results were published Feb. 2, 2026.

Data from NASA's Juno spacecraft show Jupiter is slightly smaller and more flattened than earlier estimates. Scientists analyzed radio occultation measurements from 13 Juno flybys and included the effects of zonal winds. The new analysis finds Jupiter is about 8 kilometers narrower at the equator and about 24 kilometers flatter at the poles than previous values. The findings were published Feb. 2, 2026, in Nature Astronomy. Key findings: - Juno used radio occultation during 13 flybys to probe through Jupiter's dense atmosphere and ionosphere. - Accounting for zonal winds, the equatorial width is about 8 kilometers less and the polar flattening about 24 kilometers greater than earlier estimates. - Earlier physical-dimension values were based on six radio occultation experiments from the Pioneer and Voyager missions in the 1970s. - In radio occultation, Juno transmits radio signals to NASA's Deep Space Network; bending and delays in those signals through the ionosphere let scientists infer temperature, pressure and electron density at different depths. - The study appeared in Nature Astronomy on Feb. 2, 2026, and the Juno mission is managed by NASA's Jet Propulsion Laboratory. Summary: The revised measurements refine Jupiter's physical shape and will serve as a calibration reference for modeling giant exoplanets. Undetermined at this time.