Astronomers using the Hubble Space Telescope have discovered a massive 10-sided atmospheric wave encircling Saturn’s south pole. Roughly 104,000 miles across, the newfound decagon is a geometric counterpart to the planet’s famous northern hexagon, marking the first time a regular-sided jet pattern has been observed in Saturn’s southern hemisphere.
Saturn is doubling down on geometry. More than four decades after NASA’s Voyager missions first discovered in 1988 a bizarre six-sided jet stream locked over the gas giant’s north pole, researchers have tracked an even larger multi-sided wave at the opposite end of the planet. Published in the journal Science Advances, the discovery reveals a 10-sided atmospheric structure spanning roughly 104,250 miles wide, with each straight-looking side stretching approximately 10,425 miles long.
The scale of the phenomenon is immense. Planetary scientists note that the entire decagon could easily swallow a dozen Earths laid end to end. Centered near 63 degrees south latitude, the wave rides a powerful eastward circumpolar jet stream, extending vertically through multiple layers of the atmosphere rather than remaining confined to a single cloud deck.
How Amateur Astronomers and Hubble Cracked the Southern Pole
Catching the decagon required patience, good seeing conditions, and a planetary alignment that finally brought Saturn’s southern hemisphere back into Earth-based view. Because of the planet’s long orbit and axial tilt, the southern pole was hidden from Earth between 2012 and 2023. Even NASA’s Cassini spacecraft, which orbited the ringed world from 2004 to 2017, recorded a warm polar vortex and a southern cyclone but detected no long-lived polygonal jet.
The trail began on the ground. Amateur observers Trevor Barry in Australia and Jean-Paul Oger, coordinating their work through the Planetary Virtual Observatory Laboratory managed by the University of the Basque Country, began capturing suggestive undulating bands at the south pole across 2024 and 2025.
Agustín Sánchez-Lavega, lead author of the study, later advised Trevor Barry to focus on the emerging wave pattern rather than a ripple, noting that Amy Simon’s 2023 Hubble data showed early signs of the structure’s formation.
When lead author Agustín Sánchez-Lavega and his colleagues went back through archival data from Hubble’s Outer Planet Atmospheres Legacy (OPAL) program, they found the pattern already faintly present in 2023 imagery. OPAL captures annual, consistently calibrated portraits of the outer planets using Wide Field Camera 3, allowing researchers to track slow evolutionary changes rather than isolated snapshots.
Contrasting the Decagon With Saturn’s Iconic Northern Hexagon
While the northern hexagon has maintained a stable, dark-edged appearance for over forty years, the southern decagon exhibits distinct behaviors that suggest it is still actively developing. Unlike its northern sibling, the decagon’s features vary in darkness across its structure, pointing to an ongoing evolutionary process in the atmosphere.
| Polar Feature | Hemisphere | Approximate Width | Number of Sides | Discovery / Confirmation |
|---|---|---|---|---|
| Hexagon | North | ~20,000 miles (32,000 km) | 6 | 1988 (Voyager data) |
| Decagon | South | ~104,250 miles (167,820 km) | 10 | 2023–2025 (Hubble & Ground Data) |
The number of lobes in a planetary wave directly relates to the width, speed, and shear of the jet stream carrying it. Discovering a 10-sided wave demonstrates that polygon-making is an inherent capability of Saturn’s global meteorology rather than a one-off northern anomaly. Laboratory experiments using spinning fluids have long produced various polygonal patterns, but researchers are still working out why this specific southern wave formed now.
Unresolved Questions and What Researchers Watch Next
The decagon moves slowly, taking about 800 days to complete a full rotation around Saturn. Because Hubble images taken through different wavelength filters probe varying depths in the hazes and clouds, researchers confirmed that the polygon leans with altitude, appearing to slide slightly as wavelengths change.
Scientists plan to utilize both Hubble and the James Webb Space Telescope, alongside advanced computer models, to monitor the structure’s three-dimensional profile and longevity. A key milestone to watch arrives in 2032, when solar radiation peaks at the decagon’s latitude of 60 degrees south—a juncture that will test whether the wave breaks apart or grows increasingly robust.
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