Plate Nº 91 · recorded October 10, 2026
Space & AstronomyReported finding
Hubble Spots a Sudden 10-Sided Wave at Saturn's South Pole
Hubble detected a giant 10-sided wave encircling Saturn's south pole — the first pattern of its geometry in the southern hemisphere. Researchers confirmed its emergence only since 2023.
By Nathan Brooks3 min read683 words
In brief
- NASA's Hubble detected a 10-sided atmospheric wave at Saturn's south pole, the first such pattern ever seen in the planet's southern hemisphere.
- Published September 3, 2026 in Science Advances (Vol. 12, Issue 36); lead author Agustín Sánchez-Lavega, University of the Basque Country.
- The decagon appears in Hubble data going back to 2023 but was absent from Cassini observations collected between 2004 and 2017.
- Saturn's northern hexagon has remained stable for more than 40 years; the southern decagon is currently strengthening, scientists say.
- Two amateur astronomers, Trevor Barry and Jean-Paul Oger, first spotted the faint precursor in 2024 ground-based images.
Hubble has detected a giant 10-sided atmospheric pattern encircling Saturn's south pole — the first wave of this geometry ever recorded on the planet's southern hemisphere. Scientists at NASA's Goddard Space Flight Center say the structure has no precedent in 40 years of polar imaging.
What did the telescope reveal?
The finding, published September 3, 2026 in Science Advances, draws on Hubble's Outer Planet Atmospheres Legacy (OPAL) program, which has imaged the outer planets annually for more than a decade. Researchers reconstructed the feature's growth using Hubble frames going back to 2023. Earlier images contained faint precursors; recent views show the decagon as a sharp, repeating band.
The wave's apparent position shifts slightly with the wavelength Hubble uses. Different wavelengths probe different altitudes within Saturn's atmosphere, and that drift indicates the wave extends through several atmospheric layers rather than sitting at the cloud tops alone.
How did the discovery unfold?
Saturn's long seasonal cycle gradually tipped its south pole back toward Earth, exposing territory hidden from ground-based observers. In 2024 images, lead author Agustín Sánchez-Lavega of the University of the Basque Country, Spain, along with amateur astronomers Trevor Barry and Jean-Paul Oger, noticed a faint, wavy band near the pole. By 2025, ground-based images confirmed the structure had sharpened into a decagon.
Researchers then turned to Hubble. The space-based telescope escapes the blurring Earth's atmosphere imposes, so it can see Saturn cleanly through a full rotation.
"Given Saturn's symmetry in its north-south jet stream system, we have been searching for a counterpart to Saturn's northern hexagon on the south pole in Hubble images since 1990," Sánchez-Lavega said. "Images from NASA's Cassini spacecraft, which orbited Saturn between 2004 and 2017, showed no inkling of a long-lived formation, either. The Hubble data confirmed the feature's presence back to 2023."
What makes this wave different from Saturn's famous hexagon?
Saturn's northern hexagon, a six-sided jet stream pattern, has held its shape for at least four decades. The southern decagon shares that geometric regularity but breaks a long streak of expectations. No comparable signal shows up in Cassini data from 2004 to 2017, and three decades of Hubble work before 2023 turned up nothing similar.
"We've never seen anything quite like this in Saturn's southern hemisphere," said Amy Simon, study co-author and OPAL principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The northern hexagon has been there every time we've looked for more than 40 years. This feature is different — it appears to be strengthening, giving us the rare opportunity to watch a giant atmospheric pattern develop."
Why did the decagon appear now?
Scientists cannot yet say. The decagon lies within the same powerful jet stream that hosts the northern hexagon, but the trigger for its emergence remains unknown. Simon called that mystery the most intriguing part of the finding.
"The question is, why did it suddenly form now when we haven't seen one before?" she said.
What comes next?
Researchers will keep monitoring Saturn with Hubble and the James Webb Space Telescope, and they will run computer models of jet-stream behavior to test what conditions could spawn a stable decagon. The team also wants to know:
- Whether the decagon will settle into a stable, decades-long structure like the northern hexagon, or keep evolving
- How deeply it reaches into Saturn's lower atmosphere
- Whether it can shed light on weather systems operating on other worlds, including Earth
Co-author Mike Wong of the University of California, Berkeley emphasized the value of long-running surveys. "A lot of the discoveries we see coming from OPAL are not just based on one observation, but on years and years of data. Regular observations over time are enabling a lot of new findings."
The pattern's eventual fate — persistent landmark or temporary flare — will determine whether Saturn now hosts two long-lived geometric waves or one enduring hexagon and a short-lived curiosity in the south.
via science.nasa.gov (Original)
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