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Astronomers detect a 10-sided decagon forming at Saturn's south pole
New CapabilitiesThe first large polygonal jet pattern in the planet's southern hemisphere, visible in archival images since 2023
3 days ago: Team announces decagon discovery in Science AdvancesNew here? Follow stories to track developments over time. Create a free account to get updates when stories you care about change.
Overview
Updated 1 hour agoSaturn's north pole has worn a six-sided hexagon for more than 40 years. Now Hubble Space Telescope images show a 10-sided decagon emerging at the planet's south pole — the first large polygonal jet pattern ever seen in that hemisphere.
The wave spans roughly 168,000 kilometers and sits near 60 degrees south latitude, riding an eastward jet stream that moves about 420 kilometers per hour. It rotates slowly, taking about 800 days for one full turn.
Amateur astronomers analyzing ground-based images first flagged the odd shape, and archival Hubble observations show the structure emerging as early as 2023. The decagon sharpened into a clear pattern by 2025. Scientists will track whether it stabilizes like the northern hexagon, breaks apart, or strengthens as Saturn's southern summer peaks in 2032.
Why it matters
The decagon is a live experiment in planetary atmosphere physics — watching a giant geometric wave either stabilize like Saturn's hexagon or break apart.
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Key Indicators
10
Number of sides in the wave
The decagon is the first large polygonal jet pattern seen in Saturn's southern hemisphere.
~168,000 km
Width of the decagon
Each side measures about 16,800 kilometers.
~800 days
Time for one full rotation
The wave crawls compared to the 420 km/h jet stream carrying it.
2023
Year the structure began forming
Archival Hubble images show subtle hints of the decagon starting in 2023.
Related Media
NASA's Hubble Tracks New Decagon Encircling Saturn's South Pole - NASA Science
Decagon on Saturn's South Pole (Color) - NASA Science
Images from Openverse under Creative Commons licenses.
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Astronomers detect a 10-sided decagon forming at Saturn's south pole
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People Involved
Agustin Sanchez-Lavega
Lead author of the decagon study, planetary scientist
Leading the team tracking the wave's evolution
Amy Simon
OPAL principal investigator, NASA Goddard Space Flight Center
Co-author of the decagon study
Michael Wong
Planetary scientist, UC Berkeley Space Sciences Laboratory
Co-author of the decagon study
Organizations Involved
Hubble Space Telescope
Space telescope
Primary instrument tracking the decagon
Space telescope operated by NASA and ESA that has photographed the outer planets annually since 2014 through the OPAL program.
NASA Goddard Space Flight Center
Federal research center
Leads the OPAL program, co-authored the decagon study
NASA center that leads Hubble's Outer Planet Atmospheres Legacy program and co-authored the decagon study.
University of the Basque Country
Public university
Lead institution for the decagon study
Public university in Bilbao, Spain, whose planetary scientists led the decagon study.
UC Berkeley Space Sciences Laboratory
University research lab
Co-authored the decagon study, analyzed the anticyclone
Research lab that co-authored the decagon study and analyzed the anticyclone vortex possibly driving the wave.
Timeline
November 1980 September 2026
5 events
Latest: 3 days ago
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-
Team announces decagon discovery in Science Advances
Latest PublicationResearchers from Spain, NASA, and UC Berkeley publish the decagon's characterization, dynamics, and formation hypothesis.
-
Anticyclone at 55 degrees south darkens, decagon sharpens
ObservationA compact anticyclone vortex darkens sharply, and the decagon pattern becomes clearly defined in Hubble images.
-
Archival Hubble images show first subtle hints of decagon
ObservationHubble's OPAL program images begin to show faint traces of a 10-sided pattern near 60 degrees south latitude.
-
Cassini observes partial southern hemisphere structure
ObservationThe Cassini spacecraft observed a partial polygonal structure in Saturn's southern hemisphere, but its dynamics were never characterized.
-
Voyager 1 flies past Saturn, reveals north polar hexagon
DiscoveryVoyager 1's flyby captured the six-sided jet pattern at Saturn's north pole, later confirmed by Voyager 2 in 1981 and identified in the data by 1988.
Historical Context
3 moments from history that rhyme with this story — and how they unfolded.
1831-present
Jupiter's Great Red Spot (1831-present)
Astronomers have continuously observed Jupiter's Great Red Spot, an anticyclone wider than Earth, since the 1830s. It has shrunk in recent decades but remains a distinct feature after nearly two centuries.
Then
The spot became the benchmark for long-lived planetary storms.
Now
It fed the assumption that giant-planet weather features persist for very long stretches, which the decagon now challenges.
Why this matters now
The study team notes features like the Great Red Spot create the impression that outer planets are timeless. Saturn's decagon, appearing and changing within a few years, shows how changeable these planets can be.
1980-1988
Saturn's north polar hexagon (1980-1988)
Voyager 1 and 2 flew past Saturn in 1980 and 1981 and photographed a striking six-sided cloud pattern circling the north pole. Researchers identified the hexagon in the Voyager data by 1988. The Cassini mission later confirmed it with decades of close observations.
Then
Scientists spent years trying to explain how a jet stream could carve a near-perfect hexagon.
Now
The hexagon became the benchmark for polygonal planetary weather and has persisted through every observation since.
Why this matters now
The newly discovered decagon is the first large polygonal wave found in Saturn's southern hemisphere. Its evolution will show whether such patterns are common on gas giants or a one-off.
1989-1994
Neptune's Great Dark Spot (1989-1994)
Voyager 2 photographed a large dark storm in Neptune's atmosphere in 1989. When the Hubble Space Telescope looked again in 1994, the spot had vanished.
Then
The spot was the first major planetary storm observed to disappear between campaigns.
Now
It proved giant-planet weather features can be transient, appearing and vanishing within a few years.
Why this matters now
The decagon may be similarly transient. Its fate will show which planetary weather patterns endure and which evaporate.
Sources
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