NASA's Juno spacecraft has found that Jupiter is slightly smaller and more flattened than scientists previously believed. New data shows the gas giant is about 5 miles (8 kilometers) narrower at its equator and 15 miles (24 kilometers) flatter at its poles compared to earlier measurements. These precise findings, published on February 2, 2026, in Nature Astronomy, update decades-old estimates and offer new insights into the solar system's largest planet.[channelnewsasia+3]
Unveiling Jupiter's True Shape
The Juno mission achieved these updated measurements using advanced radio science data. Scientists analyzed radio occultation data from 13 flybys of Jupiter. During these flybys, Juno beamed radio signals back to NASA's Deep Space Network on Earth.As these signals passed through Jupiter's charged upper atmosphere, called the ionosphere, gases bent and delayed them.By carefully measuring the changes in frequency caused by this bending, researchers could calculate the temperature, pressure, and electron density of Jupiter's atmosphere at various depths.This method allowed the team to account for the effects of Jupiter's powerful zonal winds, which slightly alter the planet's gaseous shape.[science+7]
Previous understandings of Jupiter's size and shape relied on data gathered by NASA's Voyager and Pioneer robotic spacecraft in the late 1970s.Those missions used six radio occultation experiments.Juno's superior precision has now refined these long-standing figures.The spacecraft launched in 2011 and has been orbiting Jupiter since 2016, continuously sending back raw data to Earth.NASA extended the Juno mission in 2021, which allowed scientists to collect the detailed observations needed for these fine-tuned measurements.[channelnewsasia+9]
Why New Measurements Matter
These small adjustments to Jupiter's dimensions are important for understanding the gas giant's internal structure. "Textbooks will need to be updated," said Yohai Kaspi, a planetary scientist at the Weizmann Institute of Science in Israel and a study co-author.He added that Jupiter's actual size has not changed, but the way scientists measure it has.The new data shows Jupiter has an equatorial diameter of 88,841 miles (142,976 kilometers), which is about 5 miles (8 kilometers) smaller than previous measurements.Its polar diameter is 83,067 miles (133,684 kilometers), about 15 miles (24 kilometers) smaller than earlier estimates.[livescience+5]
Jupiter, like Earth, is not a perfect sphere. Its rapid rotation, completing a spin every 9.9 hours, causes it to bulge at the equator and flatten at the poles.This shape is known as an oblate spheroid. The new data indicates Jupiter is even more flattened than previously known, with its equator being about 7% larger than its poles.For comparison, Earth's equator is only about 0.33% larger than its diameter at the poles."These few kilometers matter," said Eli Galanti, another study co-author and a gas giants expert at the Weizmann Institute of Science.He explained that "shifting the radius by just a little lets our models of Jupiter's interior fit both the gravity data and atmospheric measurements much better."[sci+7]
More accurate dimensions help astronomers create better models of Jupiter's deep interior. Scientists use Jupiter's exact radius as a crucial standard for modeling giant exoplanets, which are planets outside our solar system.Having a more precise shape helps astronomers better interpret data from these distant planets when they pass in front of their host stars.This improved understanding of Jupiter's structure could also refine theories about how giant planets form and evolve, not just in our solar system but across the cosmos.[science+3]
Juno's Broader Discoveries
Beyond its shape and size, the Juno mission has revealed other surprising details about Jupiter. One significant finding is that Jupiter's core is "fuzzy" or "dilute," not a dense, solid ball as some scientists had theorized.Instead, the core appears to be much larger than expected and gradually blends with the hydrogen-rich layers above it, without sharp boundaries.This discovery challenges previous theories about how Jupiter and other gas giants formed.[missionjuno+6]
Juno has also peered beneath Jupiter's dense clouds, providing the first 3D look at its atmosphere.It found that Jupiter's powerful jet streams, the strong winds that create its distinctive belts and zones, extend much deeper than expected, reaching depths of about 2,000 miles (3,200 kilometers) or even 3,000 kilometers (2,000 miles).The spacecraft also discovered previously unseen networks of vast, resilient storms swirling around both of Jupiter's poles.These and other findings from Juno continue to transform our understanding of Jupiter and its role in the solar system's history.[youtube+6]
The ongoing Juno mission, scheduled to continue investigating Jupiter through September 2025, provides unprecedented precision in mapping the planet's gravitational and magnetic fields.This work is critical for understanding the distribution of mass in Jupiter's interior and the dynamics that drive its powerful magnetic field.[science+6]
