Jupiter Revealed to Be Smaller and Flatter Than Previously Thought

New measurements from NASA's Juno spacecraft prompt updates to textbooks and models of the gas giant's interior.

Published on Feb. 4, 2026

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A new study published in Nature Astronomy has revealed that Jupiter, the largest planet in our solar system, is actually smaller and flatter than previously believed. Using data from NASA's Juno spacecraft, an international team of scientists found that Jupiter's equatorial diameter is around 5 miles slimmer than earlier estimates, and its polar diameter is about 15 miles smaller. These changes, while seemingly minor, mark a significant shift from prior measurements based on data from the Voyager and Pioneer spacecraft in the 1970s.

Why it matters

The new findings about Jupiter's size and shape will require updates to textbooks and models of the planet's interior structure and evolution. Understanding the precise dimensions of Jupiter is crucial for advancing our knowledge of how planets form and evolve in our solar system.

The details

The researchers were able to make these more accurate measurements of Jupiter by analyzing radio signals from the Juno spacecraft as it passed behind the planet from Earth's perspective. This allowed them to track the curvature of the radio signals as they passed through Jupiter's atmosphere, providing detailed maps of the planet's temperature and density. They also factored in the effects of Jupiter's powerful winds on the planet's shape.

  • The study was published in the journal Nature Astronomy on February 4, 2026.
  • NASA's Juno spacecraft has been orbiting Jupiter since 2016, but its mission was extended in 2021 to continue gathering data on the gas giant and its moons.

The players

Yohai Kaspi

A planetary scientist at the Weizmann Institute of Science in Israel and a co-author of the study.

Eli Galanti

A scientist who spearheaded the research in Kaspi's team.

Scott J. Bolton

The Principal Investigator of the Juno mission at Southwest Research Institute in San Antonio, Texas.

NASA's Juno spacecraft

The spacecraft that has been orbiting Jupiter since 2016 and provided the new measurements used in the study.

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What they’re saying

“Textbooks will need to be updated. The size of Jupiter hasn't changed, of course, but the way we measure it has.”

— Yohai Kaspi, Planetary scientist at the Weizmann Institute of Science

“When the spacecraft passes behind the planet, its radio communication signal is blocked and bent by Jupiter's atmosphere. This enables an accurate measurement of Jupiter's size.”

— Scott J. Bolton, Principal Investigator of the Juno mission

“It's difficult to see what's happening beneath the clouds of Jupiter, but the radio data give us a window into the depth of Jupiter's zonal winds and powerful hurricanes.”

— Yohai Kaspi, Planetary scientist at the Weizmann Institute of Science

What’s next

The researchers plan to continue analyzing the data from the Juno spacecraft to further refine their understanding of Jupiter's interior structure and atmospheric dynamics.

The takeaway

This study marks a significant shift in our understanding of the solar system's largest planet, with implications for how we model planetary formation and evolution. The new, more precise measurements of Jupiter's size and shape will require updates to textbooks and scientific models, advancing the field of astronomy.