Recent research utilizing data from NASA’s Juno spacecraft has resulted in the most precise measurements of Jupiter’s size in 50 years, revealing that the largest planet in our solar system is thinner and flatter than previously thought.
Hubble’s observations of Jupiter highlight an ever-changing landscape resulting from its turbulent atmosphere. Image credits: NASA / ESA / Hubble / Amy Simon, NASA Goddard Space Flight Center / Michael H. Wong, University of California, Berkeley / Joseph DePasquale, STScI.
“The previous understanding of Jupiter’s shape was based on just six measurements made by NASA’s Voyager and Pioneer missions nearly 50 years ago, utilizing radio waves sent to Earth,” explained Dr. Eli Galanti from the Weizmann Institute of Science.
“While those missions laid the groundwork, we now have the unique chance to analyze 26 new measurements obtained from NASA’s Juno spacecraft.”
“By determining Jupiter’s distance and observing its rotation, we can accurately derive its size and shape,” stated Professor Yohai Kaspi of the Weizmann Institute of Science.
“However, to achieve highly precise measurements, we require more advanced techniques.”
“Juno’s passage behind Jupiter opens up new scientific opportunities,” commented Dr. Scott Bolton, Juno’s principal investigator and a researcher at the Southwest Research Institute.
“As the spacecraft navigates behind the planet, its radio communication signals become obstructed and bent by Jupiter’s atmosphere, enabling precise size measurements.”
“By tracking the curvature of these radio signals as they pass through Jupiter’s atmosphere, we were able to generate a detailed map of the planet’s temperature and density, providing the clearest insight yet into Jupiter’s dimensions,” explained Dr. Maria Smirnova, a student at the Weizmann Institute of Science.
The study revealed that Jupiter has a polar radius of 66,842 km, an equatorial radius of 71,488 km, and an average radius of 69,886 km—12, 4, and 8 km lower than prior estimates respectively.
“It’s time to update textbooks. While Jupiter’s size remains unchanged, our measurement techniques have significantly evolved,” noted Professor Kaspi.
“Those few kilometers matter. A slight shift in radius greatly improves how well our internal model aligns with both gravity data and atmospheric metrics,” commented Dr. Galanti.
“Our advanced models of Jupiter’s internal density structure illustrate how sophisticated geometries can help reconcile models with measurements,” said Dr. Marjan Ziv, also a student at the Weizmann Institute of Science.
Previous estimates overlooked Jupiter’s powerful winds. By considering these winds in their calculations, scientists resolved a long-standing contradiction.
“It’s challenging to decipher details beneath Jupiter’s clouds, but radio data provides insights into the depths of Jupiter’s zonal winds and intense hurricanes,” stated Professor Kaspi.
The findings are documented in a study published in Nature Astronomy.
_____
E. Galanti et al. 2026. Jupiter’s Size and Shape. Nat Astron 10, 493-501; doi: 10.1038/s41550-026-02777-x
Source: www.sci.news
