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Juno Data Show Jupiter Is Slightly Smaller and More Flattened Than Thought

Using Juno radio occultations that account for strong zonal winds, researchers produced tighter constraints on the gas giant's interior.

An enhanced-color image, using raw data from the JunoCam instrument aboard NASA's Juno spacecraft, shows the planet Jupiter, with a shadow of its moon Ganymede on the left, released by NASA on April 21, 2022. NASA/JPL-Caltech/SwRI/MSSS/Image processing by Thomas Thomopoulos/Handout via REUTERS
Jupiter is slightly smaller than previously estimated — about 8 kilometers (about 5 miles) less wide at the equator and 24 kilometers (about 15 miles) flatter at the poles. Weizmann Institute of Science

Overview

  • Peer-reviewed results in Nature Astronomy (Feb. 2) report an equatorial diameter of 88,841 miles (142,976 km) and a polar diameter of 83,067 miles (133,684 km), both smaller than long-standing estimates.
  • The analysis explicitly included wind effects and reduced measurement uncertainty by about tenfold compared with Voyager and Pioneer era values.
  • Dimensions were derived from multiple behind-planet passes during Juno’s extended mission, with radio signals bent through Jupiter’s atmosphere and tracked by NASA’s Deep Space Network.
  • The updated figure shows the equator is roughly 7% wider than the pole-to-pole diameter, indicating a more oblate planet than previously calculated.
  • The refined radii improve consistency among gravity data, atmospheric observations and interior models, and the team plans to apply the technique to ESA’s JUICE mission.