Saturn's south pole grew a giant 10-sided pattern: meet the decagon, the famous hexagon's stranger cousin
Hubble has confirmed a giant, evolving 10-sided jet-stream pattern, a decagon, encircling Saturn's south pole, a southern counterpart to the planet's celebrated north-pole hexagon. Here is what the Saturn decagon is, how it compares to the hexagon, and why these regular shapes form at all.
Astronomers using the Hubble Space Telescope have confirmed a 10-sided jet-stream pattern, a decagon, encircling Saturn's south pole, reported in Science Advances on 2 September 2026 and featured as NASA's Astronomy Picture of the Day on 8 September. It is a southern counterpart to Saturn's famous north-pole hexagon, the six-sided feature first seen by the Voyager and Cassini missions. The decagon is an atmospheric wave pattern in a fast jet stream, not a solid object, and it is genuinely recent: NASA's Cassini mission saw no such pattern while orbiting Saturn from 2004 to 2017, with hints appearing in Hubble imaging only from 2023 onward. The leading explanation is that waves at the boundary between fast and slow-moving bands lock the jet into a regular polygon, though the exact mechanism is not settled.
Saturn is the solar system's great geometer, and it has just added a shape to its collection. Astronomers have confirmed that a 10-sided pattern, a decagon, wraps around the planet's south pole, a southern echo of the six-sided hexagon that has fascinated people since the Voyager era. The finding was published in Science Advances on 2 September 2026 and picked as NASA's Astronomy Picture of the Day on 8 September. Here is what the decagon is, how it stacks up against the hexagon everyone already knows, and why a planet grows straight-edged patterns at all.
What is the decagon at Saturn's south pole?
The decagon is a 10-sided pattern traced by a jet stream circling Saturn's south pole. It is not a solid structure or a single storm you could point at; it is the shape that a fast river of wind settles into, drawn out over time in Hubble imaging. Researchers describe it as a giant, evolving, regular-sided wave in the atmosphere. The team frames it as the first regular-sided polygon pattern confirmed in Saturn's southern hemisphere, a claim worth attributing to the study rather than stating flatly, since polar features on Saturn have a long history of surprising observers.
Importantly, it is genuinely new rather than long-overlooked: NASA's Cassini spacecraft, which studied Saturn up close from 2004 to 2017, saw no such pattern, and it appears in Hubble data only from 2023 onward. The team describes it as having formed recently, which is itself part of the puzzle, why a 10-sided pattern should appear now when none was there before.
Does Saturn's south pole have a hexagon too, like the north?
This is the natural question, and the answer is what makes the story interesting. Saturn's north pole hosts the celebrated hexagon, a six-sided jet-stream pattern first spotted by NASA's Voyager probes and studied in detail by the Cassini mission. The south pole, by contrast, has long been known for a giant hurricane-like vortex but not a clean polygon. The decagon is the news precisely because it gives the south its own regular-sided pattern, and a different number of sides, inviting direct comparison with the northern hexagon rather than being a copy of it.
| Feature | Saturn's north pole | Saturn's south pole |
|---|---|---|
| Shape | Hexagon (6 sides) | Decagon (10 sides), newly confirmed |
| First seen by | Voyager, then Cassini | Hubble + ground-based (2023-25) |
| Nature | Jet-stream wave pattern | Jet-stream wave pattern |
Why do these regular shapes form?
The leading explanation is about waves at a boundary. Where a fast jet stream runs alongside slower-moving air, the interface can become unstable and ripple; under the right conditions those ripples lock into a stable, repeating pattern that traces out a regular polygon. The number of sides is thought to depend on details like the jet's speed, the wind shear and the size of the disturbances, but exactly why the north settles into six and the south into ten is not understood. This is the leading account, not a closed case; the precise physics that fixes the number of sides is still an active question, and the decagon gives modellers a fresh second example to test their ideas against. For more space science, see our full science coverage, including the Roman Space Telescope.
Frequently asked questions
What is the decagon at Saturn's south pole?
It is a 10-sided pattern traced by a jet stream circling Saturn's south pole, confirmed by Hubble imaging and reported in Science Advances on 2 September 2026. It is an atmospheric wave pattern, not a solid feature, and is a southern counterpart to Saturn's north-pole hexagon.
Is the decagon like Saturn's famous hexagon?
Yes and no. Both are regular-sided jet-stream patterns at a pole, but the north pole's is a six-sided hexagon (seen by Voyager and Cassini) and the newly confirmed southern one is a 10-sided decagon. The different side count is part of what makes it scientifically interesting.
Did Saturn's south pole have a hexagon before?
The south pole was known for a large hurricane-like polar vortex rather than a clean polygon. The study reports the decagon as the first regular-sided polygon pattern confirmed there, which is why it is being compared to the long-known northern hexagon.
How did Hubble find the decagon?
By imaging Saturn repeatedly over several years, from 2023 onward, and tracking the jet stream's shape, with supporting ground-based observations. The pattern is persistent across those images, which is what let the team confirm it rather than dismiss it as a transient swirl.
What makes Saturn's polar shapes form?
The leading explanation is that instabilities and waves at the boundary between fast and slow-moving air lock the jet stream into a stable, repeating polygon. The number of sides is thought to depend on the winds and disturbances involved. The exact mechanism is still being studied.
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