Saturn's South Pole Unveils Decagonal Wave in Stunning Hubble Images
- Decagonal wave detected around Saturn's south pole on 2 Sept 2026
- Hubble, amateur astronomers and Leicester scientists collaborated
- Structure spans roughly 15,000 km, rotating slower than jet streams
- First regular‑sided pattern seen in the southern hemisphere
- Findings published in Science Advances
A ten‑sided atmospheric structure, dubbed a decagon, has been confirmed around Saturn's south pole, officials said on Thursday, 3 September 2026. The feature was first spotted in Hubble Space Telescope images taken on 28 August and was corroborated by high‑resolution photographs submitted by amateur astronomers across Europe and North America.
The discovery marks the first large, regular‑sided pattern observed in Saturn's southern hemisphere, mirroring the iconic hexagon at the north pole.
- The decagon spans roughly 15,000 km across, about half the diameter of the north‑pole hexagon (according to official data). • It rotates at an estimated 0.5 m s⁻¹, considerably slower than the surrounding jet streams that exceed 150 m s⁻¹. • Observations were collected between 2023 and 2025 as the southern hemisphere became better visible from Earth.
"The detection of a decagonal wave shows that Saturn's atmospheric dynamics are far richer than we imagined," Professor Tim Fletcher, planetary scientist at the University of Leicester, said.
The team's analysis was published in the journal Science Advances on 2 September 2026, providing the first peer‑reviewed description of the phenomenon.
How the Decagon Was Spotted: Hubble, Amateurs and Leicester Team
The Hubble Space Telescope captured the initial glimpse of the decagon during a scheduled observation of Saturn's polar regions on 28 August 2026, sources confirmed.
Using the Wide Field Camera 3, astronomers obtained a series of near‑infrared images that revealed a faint, polygonal outline against the planet's swirling clouds.
Meanwhile, a network of dedicated amateur observers, coordinated through the Planetary Virtual Observatory and Laboratory, uploaded over 200 raw frames taken with 12‑inch telescopes from sites in Spain, Australia and the United States.
Leicester researchers, led by Dr. Sarah Patel, senior researcher at the university's Space Science Centre, stitched the amateur frames with Hubble data to create a seamless mosaic that highlighted the decagon's geometry.
Advanced de‑projection algorithms corrected for Saturn's tilt and the varying illumination angles, allowing the team to measure the structure's edges with an accuracy of ±200 km.
"Combining professional and citizen‑science data gave us a clarity that would have been impossible with Hubble alone," Patel explained.
The Physics Behind a Ten‑Sided Atmospheric Pattern
The decagon is believed to be a massive Rossby wave, a type of planetary‑scale oscillation driven by the planet's rapid rotation and latitudinal temperature gradients.
In Saturn's upper atmosphere, variations in wind speed create shear zones that can trap such waves, allowing them to persist for months or even years.
Unlike the more familiar hexagonal wave, which aligns with a strong east‑ward jet at 78° N, the decagon sits at approximately 74° S, where the jet stream is weaker and more variable.
Numerical simulations run on the Met Office supercomputer suggest that a standing wave with a ten‑fold symmetry can emerge when the background flow satisfies a specific resonance condition: the phase speed of the Rossby wave matches the local mean wind speed (industry reports indicate).
"Our models show that the decagonal pattern is a natural outcome of a resonant interaction between the jet and the planet's deep‑seated convection," said Dr. Lorna Hughes, director of planetary sciences at the University of Leicester.
The wave's slower rotation implies it is anchored deeper in the atmosphere, where the density is higher and the Coriolis force exerts a stronger influence.
Comparing the South Decagon with the North Hexagon
The north‑pole hexagon, first imaged by Voyager in 1981, has remained remarkably stable for over three Saturnian years—equivalent to roughly 30 Earth years.
In contrast, the newly identified decagon appears to be more transient, with its shape changing subtly over the six‑month observation window.
Size‑wise, the hexagon stretches about 30,000 km in diameter, twice the span of the decagon, and its edges are sharper, suggesting a stronger, more coherent jet stream at the northern latitude.
Both structures share a common origin in standing Rossby waves, yet the differing jet‑stream speeds and temperature profiles on each hemisphere appear to dictate the polygonal symmetry that emerges.
Professor James Leighton, senior scientist at NASA's Jet Propulsion Laboratory, noted, "The coexistence of a hexagon and a decagon on the same planet offers a rare laboratory for testing fluid‑dynamics theories under extreme conditions."
While the hexagon has been observed in multiple wavelengths, the decagon's faint infrared signature hints at a different vertical placement within Saturn's cloud layers.
What the Discovery Means for Planetary Meteorology
The identification of a decagonal wave reshapes our understanding of how giant planets organise their atmospheric flows, experts said.
It demonstrates that Saturn can sustain multiple, distinct polygonal patterns simultaneously, a behaviour that may also occur on other gas giants such as Jupiter or even on exoplanets with rapid rotation.
Climate models of exoplanetary atmospheres, which often assume simple zonal jets, will now need to incorporate the possibility of standing wave resonances that produce regular‑sided structures.
The finding also provides a natural analogue for studying atmospheric super‑rotation, a phenomenon observed on Venus and Titan, where the atmosphere spins faster than the planet itself.
Educational outreach programmes in UK schools are already preparing lesson plans that use the decagon as a vivid example of fluid dynamics in action, linking textbook theory with real‑world space discoveries.
"Seeing a ten‑sided wave on a world so far away brings abstract mathematics to life for students," said Dr. Emily Carter, ESA education officer.
Looking Ahead: Next Steps for Saturn Research
Future observations will focus on tracking the decagon's evolution over the coming Saturnian year, a period that will see the southern hemisphere tilt further towards Earth.
The Hubble Space Telescope has been allocated additional time in its Cycle 34 programme, allowing astronomers to capture high‑resolution images every two months.
Ground‑based facilities such as the European Southern Observatory's Very Large Telescope will complement space‑based data with adaptive‑optic spectroscopy, probing the chemical composition of the wave's cloud tops.
Meanwhile, a consortium of UK universities, led by the University of Leicester, is developing a suite of three‑dimensional general‑circulation models that will simulate the interaction between deep‑seated convection and the observed polygonal waves.
"Our next goal is to predict whether the decagon will persist, morph into a different shape, or dissipate entirely," Hughes added.
If the wave proves long‑lived, it could become a prime target for a future Saturn orbiter, a mission concept currently under review by the European Space Agency and the UK Space Agency.