Researchers discover decagon-shaped structure in Saturn’s clouds

A 10-sided atmospheric structure has appeared around Saturn’s south polar region, giving researchers an unexpected counterpart to the planet’s famous northern hexagon.

The discovery was led by Agustín Sánchez-Lavega, a professor at the University of the Basque Country in Spain. The study, published in Science Advances, used images from the Hubble Space Telescope and observations gathered through a broad network of amateur astronomers.

Voyager 1 and Voyager 2 first revealed Saturn’s northern hexagon during their flybys in 1980 and 1981. The structure surrounds the planet’s north pole and has persisted for more than one Saturn year, equivalent to about 30 Earth years. Researchers had not previously seen a comparable formation in the southern hemisphere, despite Saturn’s symmetrical wind distribution and atmospheric dynamics.

As Saturn’s southern hemisphere became more visible in 2023, Hubble images showed a decagon around the south polar region instead of another hexagon. Later Hubble observations from 2024 and 2025, along with ground-based telescope images, confirmed the feature.

Some corners of the decagon appear less distinct than others. That suggests the phenomenon may still be developing and may currently be less stable than the northern hexagon. “We are really surprised by this discovery, which was completely unexpected,” Sánchez-Lavega said. He added that it opens the way for detailed research and comparisons between the two atmospheric structures in coming years. Amateur astronomers will help researchers track the decagon’s evolution regularly.

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We are really surprised by this discovery, which was completely unexpected