Saturn’s Southern Decagon: A Ten-Sided Jet Stream Unveiled

Astronomers have identified a massive, ten-sided atmospheric wave—dubbed the “decagon”—encircling Saturn’s south pole. The structure lies within a circumpolar jet at roughly 63° S latitude and spans about 104,000 mi (? 167,800 km) across, with each side about 10,000 mi long. Unlike the northern hexagon, the decagon is migrating eastward at roughly 6 mph (10 kph) and appears to be intensifying. The findings were published on September 2 2026 in *Science Advances*.

LA Times

Saturn’s atmosphere is the only known example of planetary jet streams forming polygonal shapes. The six-sided hexagon at the north pole was first imaged by Voyager in 1980-81 and remained stable for decades. Searches for a southern counterpart have spanned three decades, with Hubble observations yielding only faint hints until the recent detection. The planet’s axial tilt hides each pole from Earth for years; the south pole was largely out of view from roughly 2012 to 2023.

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north Hubble Finds 10-Sided Wave Around Saturn's South Pole Hubble Confirms Decagon Around Saturn's South Pole

• Agustín Sánchez-Lavega – Lead author, University of the Basque Country.

LA Times

• Amy Simon – NASA Goddard, principal investigator of the OPAL program.

ABC News Australia

• Mike Wong – Co-author, UC Berkeley.

ABC News Australia

• Leigh Fletcher – University of Leicester.

LA Times

• Trevor Barry – Amateur astronomer, whose backyard observations contributed to the discovery.

ABC News Australia

• NASA/ESA Hubble Space Telescope – Primary imaging platform.

Hubble Finds 10-Sided Wave Around Saturn's South Pole

• OPAL (Outer Planet Atmospheres Legacy) program – Provides yearly calibrated images of the outer planets.

Hubble Confirms Decagon Around Saturn's South Pole

• 2023 – Faint decagon signatures appear in Hubble’s OPAL archive.

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north

• Mid-2024 – Trevor Barry records ripple-like features in Saturn’s south polar collar and forwards data to Sánchez-Lavega.

ABC News Australia

• 2025-2026 – Ground-based observers and Hubble confirm a growing, ten-sided wave.

Hubble Finds 10-Sided Wave Around Saturn's South Pole

• September 2 2026 – Peer-reviewed paper announcing the decagon is published in *Science Advances*.

LA Times

• Diameter: ~104,000 mi (? 167,800 km).

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north

• Side length: ~10,000 mi (? 16,800 km).

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north

• Latitude band: centered near 63° S.

Hubble Space Telescope Uncovers Rare Decagon Cloud Formation on Saturn

• Drift speed: eastward at ~6 mph (10 kph).

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north

• Vertical extent: multi-layered; the wave shifts position in different spectral filters, indicating depth through several atmospheric layers.

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north

Amy Simon stressed that OPAL’s decade-long imaging was essential for turning “a hint” into a measurable wave.

ABC News Australia

Trevor Barry, a former mine worker turned amateur astronomer, captured the first clear ground-based images of the southern polar disturbance in mid-2024. His timing, location data, and high-resolution frames were incorporated into the peer-reviewed analysis, illustrating the role of citizen scientists when space-based assets cannot observe continuously.

ABC News Australia

Sources differ on the exact size of the decagon. Both measurements derive from Hubble imaging, reflecting uncertainties in defining the wave’s outermost edges. No consensus yet exists on how long the decagon will persist or whether its geometry might evolve.

Astronomers using Hubble found a new roughly 104,000-mile-wide ten-sided storm forming at Saturn’s south pole, a geometric twin to the famous hexagon that has long circled the north

• “From 2024, mid 2024, I started to capture what I described to my professor as a ripple impinging down, bright spots forming a ripple that impinged down into the south polar collar of Saturn,” — Trevor Barry

ABC News Australia