NASA’s Hubble Space Telescope has discovered a massive, 10-sided atmospheric wave larger than Earth encircling Saturn’s south pole. Dubbed a decagon, the 104,250-mile-wide pattern marks the first time a large regular-sided jet pattern has been observed there.
For decades, astronomers have tracked the famous six-sided hexagonal jet stream swirling around Saturn’s north pole, a striking feature first spotted by the Voyager spacecraft in the 1980s. While scientists long suspected that a southern counterpart might exist, decades of observation—including imagery captured by the Cassini spacecraft during its 2004 to 2017 orbit—showed no sign of a comparable long-lived formation, according to lead author Agustín Sánchez-Lavega.
How the Planetary Virtual Observatory Laboratory and Hubble Spotted the Decagon
The breakthrough discovery came through crowdsourced astronomy via the OPAL program. Agustín Sánchez-Lavega of the University of the Basque Country teamed up with amateur astronomers Trevor Barry and Jean-Paul Oger to examine ground-based images submitted to the Planetary Virtual Observatory Laboratory website. In 2024, the group noticed a subtle undulating band near Saturn’s southern pole.
Subsequent observations by the Hubble Space Telescope confirmed that the colossal decagon was already present as early as 2023. According to NASA, the 10-sided atmospheric wave sits within one of Saturn’s powerful jet streams, centered around 63 degrees south latitude, and has grown increasingly defined over time.
Comparing the Northern Hexagon to the Southern Decagon
Saturn’s northern pole has remained famous for nearly five decades for its hexagon jet stream, which spans 20,000 miles (32,000 kilometers) across. By contrast, the newly discovered southern decagon spans an astonishing 104,250 miles (167,820 kilometers), easily making it a region far wider than Earth.
This massive scale makes it the first time a large regular-sided jet pattern has been observed there. Commenting on the significance of the findings, Sánchez-Lavega noted that the discovery suggests the northern hexagon is not as extraordinary as previously thought
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Investigating Why the Giant Atmospheric Ring Formed Now
Scientists currently view the 10-sided atmospheric wave as an entirely new type of phenomenon evolving on the gas giant. However, the sudden appearance of the structure has left researchers searching for answers regarding its timing.
The most intriguing part to me is that this seems to have just formed recently. The question is, why did it suddenly form now when we haven’t seen one before?
Amy Simon, study co-author and OPAL principal investigator, NASA’s Goddard Space Flight Center in Greenbelt, Maryland
To solve this mystery, the research team hopes to enlist more observatories, including the James Webb Space Telescope, to track how the decagon continues to evolve.
