Jupiter, the largest planet in the solar system, is slightly smaller and more flattened than scientists once believed, according to new findings from NASA's Juno spacecraft.
By studying data from 13 close flybys of Jupiter, researchers found that the gas giant is around 8 kilometres narrower at the equator and 24 kilometres flatter at the poles than earlier estimates suggested. The updated measurements also account for the powerful winds that circle the planet, known as zonal winds.
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The discovery was made using a technique called radio occultation, which allows scientists to study Jupiter's interior despite its thick and cloudy atmosphere. During these experiments, Juno sends radio signals back to Earth. As the signals pass through Jupiter's ionosphere, they bend and slow down. By tracking these changes, scientists can calculate temperature, pressure and density at different depths of the planet's atmosphere.
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Photo Credit: science.nasa.gov
Until now, Jupiter's size had been based on limited data collected during six radio occultation experiments carried out by NASA's Pioneer and Voyager missions in the 1970s.
Scientists say the new measurements are important not just for understanding Jupiter, but also for studying planets beyond our solar system. Jupiter's size is often used as a reference point for modelling giant exoplanets orbiting distant stars. A more accurate measurement will help astronomers better interpret observations of these faraway worlds.
The findings were published on February 2, 2026, in the journal Nature Astronomy. The Juno mission is managed by NASA's Jet Propulsion Laboratory in California.
