Jupiter is smaller and flatter than we thought, reveals juno probe

Jupiter imaged by the Juno spacecraft, with the shadow of the massive moon Ganymede to the left. Data from Juno suggests that Jupiter is flatter than previously thought, according to a new study. (Image credit: Image data: NASA/JPL-Caltech/SwRI/MSSS Image processing by Thomas Thomopoulos © CC BY)

doi.org/10.1038/s41550-026-02777-x
Credibility: 989
#Júpiter

A recent discovery is prompting textbook updates: the largest planet in the solar system, Jupiter, is slightly smaller and flatter at the poles than previously believed

These new, much more precise measurements come from data collected by NASA’s Juno probe, which has been orbiting the planet since 2016.

For a long time, Jupiter’s dimensions were based on observations made about 50 years ago by the Pioneer and Voyager probes.

At that time, they used radio beams to estimate its size, but the amount of data was limited.

Now, with Juno making numerous close passes and collecting a huge amount of information-especially in recent years-scientists have been able to refine everything with impressive precision, adjusting measurements by hundreds of meters.

New calculations show that Jupiter’s polar radius (from the center to one of the poles) is approximately 66,842 km, about 12 km less than the previous value.

The equatorial radius (from the center to the equator) is approximately 71,488 km, about 4 km smaller than previously estimated.

In terms of diameter, this means the planet is about 8 km narrower at the equator and approximately 24 km more “flattened” between the poles.

These small differences are very important.

Jupiter is not a perfect sphere: its very rapid rotation (a day lasts less than 10 hours) causes it to expand at the equator and flatten at the poles, an effect called oblateness.

Furthermore, strong atmospheric winds and the planet’s internal structure, with less dense outer layers, influence this shape.

The Juno probe measured how radio signals bent as they passed through the atmosphere and when they were blocked by the planet, allowing the inclusion of these wind effects and improving the models.

With these updates, models of Jupiter’s interior now better match gravity data with atmospheric observations.

This helps scientists better understand how this gas giant works internally.

Since Jupiter was likely the first planet to form in the solar system, studying its characteristics brings us closer to understanding how the entire system-including Earth-arose and evolved.

The findings also help interpret data from similar giant planets found in other star systems.

Ultimately, while Jupiter remains by far the largest planet in our solar system, it has been found to be somewhat more compact and flattened than previously thought in textbooks.

Science advances, and with it, our view of the universe becomes more precise and fascinating.

Published in 02/09/2026 01h03

Portuguese version

Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.

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