Jupiter, the largest planet in the solar system, is slightly smaller and flatter than scientists have believed for decades, according to new research based on data from NASA’s Juno spacecraft.
Using highly detailed radio measurements collected by Juno, researchers refined estimates of the planet’s size and shape. Although the differences are subtle, scientists say they are scientifically meaningful. More precise measurements improve understanding of Jupiter’s interior and strengthen the models used to study gas giants beyond the solar system. The findings were published on February 2 in Nature Astronomy.
The study indicates that earlier calculations slightly overstated Jupiter’s dimensions. The planet itself has not changed; rather, advances in measurement techniques have made it possible to determine its size with greater accuracy.
Yohai Kaspi, a planetary scientist at the Weizmann Institute of Science and a co-author of the study, said the updated results will require revisions to scientific reference materials. He explained that modern spacecraft tracking and radio science now offer a level of precision that was simply not achievable several decades ago.
Juno delivers more precise data on Jupiter’s size and shape
For nearly 50 years, scientists relied on measurements gathered during six flybys by the Voyager 1, Voyager 2, Pioneer 10, and Pioneer 11 missions. Those observations, made using radio signals, became the standard reference for Jupiter’s size and shape. The long-standing picture is now being refined by far more precise data from NASA’s Juno spacecraft.
Since arriving at Jupiter in 2016, Juno has collected a much larger volume of radio measurements, particularly over the past two years. Using this expanded dataset, researchers were able to determine Jupiter’s dimensions with precision down to about 1,300 feet (400 meters) in each direction. Scientists say both the quantity and quality of Juno’s data greatly surpass what was available from earlier missions, allowing for a significantly more accurate assessment of the planet’s size and shape.
Radio signals reveal Jupiter’s subtle distortions, showing it’s smaller than believed
To calculate the updated figures, researchers analyzed how radio signals transmitted from Juno to Earth bent as they passed through Jupiter’s dense atmosphere before disappearing entirely when the planet blocked them. Subtle variations in the signals revealed how Jupiter’s powerful winds slightly distort its shape. Scientists accounted for these atmospheric effects before determining the planet’s size.
BREAKING 🚨: New data from NASA Juno shows Jupiter is smaller than previously believed!
Researchers say the planet is 8 km narrower and 24 km flatter than the measurements we've used for the past 50 years!!
"Textbooks will need to be updated." pic.twitter.com/o7fkGHYwKo
— Latest in space (@latestinspace) February 4, 2026
The revised measurements show that the distance from Jupiter’s pole to its center is 41,534 miles (66,842 km) about 7.5 miles (12 km) smaller than earlier estimates. Jupiter’s equatorial radius measures 44,421 miles (71,488 km) roughly 2.5 miles (4 km) less than previously thought.
Why a couple of miles make a difference
According to Eli Galanti, co-author of the study and a gas giant expert at the Weizmann Institute of Science, even small adjustments make a meaningful difference. He explained that slight changes in Jupiter’s radius allow models of the planet’s interior to better align with both gravity data and atmospheric measurements.
Researchers say the refined measurements provide a clearer picture of Jupiter’s internal structure. They also help scientists more accurately interpret observations of massive planets orbiting other stars, where direct measurements are limited.
Clues to how planets form
Kaspi noted that the findings also offer valuable insight into how planetary systems develop. Jupiter is thought to have been the first planet to form in the solar system, and studying its interior helps researchers understand the earliest stages of planetary formation.
Scientists add that lessons learned from Jupiter may shed light on how planets like Earth eventually emerged, providing a clearer picture of how solar systems form and evolve across the universe.
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