Astronomers using NASA’s Hubble Space Telescope have discovered an enormous 10-sided atmospheric wave pattern ringing Saturn’s southern mid-latitudes, according to research published in Science Advances. Spanning roughly 10,000 miles on each side, the newly revealed decagon represents the first time scientists have observed a large, regularly shaped jet pattern in Saturn’s southern hemisphere, sharing similarities with the planet’s famous north-pole hexagon while presenting distinct structural differences.
Hubble and Ground-Based Observations Reveal the Southern Decagon
The unusual structure remained hidden from Earth for more than a decade because Saturn’s southern pole stayed tipped away from our line of sight during its long seasonal cycle, according to NASA. When the planet’s axial tilt shifted the south pole back toward Earth between 2023 and 2025, NASA’s Hubble Space Telescope and large ground-based observatories finally gained a clear view. Study lead author Agustín Sánchez-Lavega, a researcher at the University of the Basque Country in Spain, noted that his team first noticed a faint, wavy band in 2024 images alongside amateur astronomers Trevor Barry and Jean-Paul Oger using data from the Planetary Virtual Observatory Laboratory. Subsequent observations collected in 2025 provided stronger evidence that the feature had developed into a full decagon.
Atmospheric Mechanics of Saturn’s Powerful Jet Streams
The decagon is not a ring of solid clouds, but rather a giant atmospheric wave running all the way around the planet within a powerful jet stream, according to NASA. In this southern jet, wind wiggles slightly toward the pole and equator as it flows at about 260 mph, causing clouds to pile up or thin out depending on the wave’s bend. Unlike Earth’s jet streams, which get broken up by continents and mountains, Saturn’s deep layers of gas provide a clean racetrack that lets waves fall into regular patterns. Co-author Amy Simon of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, pointed out that the structure appears to be strengthening rather than remaining static.
Comparing Saturn’s Northern Hexagon and Southern Decagon
Researchers immediately compared the new southern decagon to Saturn’s well-known northern hexagon, which has held its six-sided shape since Voyager flybys in the early 1980s, according to NASA. While the northern hexagon is nearly fixed relative to Saturn’s rotation and spans about 20,000 miles wide, the southern decagon looks far less stable and only showed up recently. Images from NASA’s Cassini spacecraft, which orbited Saturn between 2004 and 2017, showed no inkling of a long-lived formation in the south either, according to Agustín Sánchez-Lavega. Computer simulations conducted by the research team showed that strong, curved jets can create polygon-like waves when nudged by storms or small bumps, helping scientists understand how giant planets sculpt their winds.
Did you know?
Saturn is the second largest planet in our solar system and hosts a massive system of moons, with a whopping 128 of its 274 observed moons just discovered in March 2025.
Frequently Asked Questions
What is the decagon on Saturn?
The decagon is a giant 10-sided atmospheric wave pattern discovered by astronomers in Saturn’s southern hemisphere, with each side stretching more than 10,000 miles long, according to NASA and published studies in Science Advances.
How does the southern decagon compare to the northern hexagon?
While Saturn’s northern hexagon has persisted for over 40 years with stable sides, the southern decagon is a newly formed, less stable structure whose corners shift in strength and position, according to researchers.
Why wasn’t the decagon discovered earlier?
For more than a decade, Saturn’s south pole was tipped away from Earth, preventing telescopes from seeing those latitudes clearly until the planet’s seasonal tilt brought the region back into view between 2023 and 2025, according to NASA.
Keep reading