Astronomers using NASA's Hubble Space Telescope have identified a giant 10-sided atmospheric wave encircling Saturn's south pole, the first time a large, regular-sided jet pattern has been observed in the planet's southern hemisphere. The findings were published in the journal Science Advances and announced by NASA's Goddard Space Flight Center on September 2. The agency last updated its release on September 4.

Unlike Saturn's long-studied northern hexagon, which has appeared in every observation for more than four decades, this feature looks new. Hubble data trace it back to 2023, and the research team reports that it appears to be strengthening rather than holding steady.

The result matters beyond planetary science circles for a specific reason. It gives researchers a rare chance to watch a large atmospheric pattern on a giant planet form and evolve, instead of studying one that was already fully developed when instruments first reached it.

A Pattern the Telescope Can Now Trace Back Three Years

The confirmation came from the Outer Planet Atmospheres Legacy program, known as OPAL, which has photographed the outer planets annually for more than a decade. By assembling several years of those observations, researchers found subtle hints of the structure emerging before it resolved into a clearly defined pattern.

We've never seen anything quite like this in Saturn's southern hemisphere, said Amy Simon, a study co-author and the OPAL principal investigator at Goddard, in the NASA release.

Simon noted that the northern hexagon has been present every time astronomers have looked across more than 40 years, and said the newer southern feature behaves differently. She described the chance to watch a giant atmospheric pattern develop as a rare opportunity.

The south pole came back into view from Earth because of Saturn's changing seasons, which gradually tilted the region toward observers.

Amateur Observers Caught the First Hint

The discovery did not begin at a space telescope. Agustín Sánchez-Lavega, the study's lead author and a researcher at the University of the Basque Country in Spain, first noticed a subtle undulating band along the southern pole in ground-based images submitted in 2024 to the Planetary Virtual Observatory Laboratory, a site the university maintains for observers worldwide.

Amateur astronomers Trevor Barry and Jean-Paul Oger noticed the band alongside him. Additional ground imagery the following year pointed more strongly toward a decagon structure.

Hubble then supplied what ground telescopes could not. Observing from above Earth's atmosphere, it delivered sharper images across full rotations of the planet without the smearing that limits ground-based work.

Sánchez-Lavega said the team had been searching Hubble images for a southern counterpart to the northern hexagon since 1990, given the symmetry of Saturn's north-south jet stream system, and that images from NASA's Cassini spacecraft, which orbited Saturn between 2004 and 2017, showed no sign of a long-lived formation either.

Depth Below the Cloud Tops Sets It Apart

One detail separates this from a passing cloud arrangement. The wave sits inside one of Saturn's powerful jet streams and extends through multiple layers of the atmosphere, which indicates a vertically extended structure rather than a cloud-level pattern.

Part of the evidence is an unusual clue. The decagon's apparent position shifts slightly between Hubble images taken at different wavelengths, and different wavelengths probe different altitudes in Saturn's atmosphere.

That depth is what makes the comparison to the northern hexagon meaningful and what makes the formation question interesting. Simon framed the central puzzle as timing rather than mechanism: why a structure of this kind would appear now, when nothing comparable has been recorded in the south before.

Comparisons with the Hexagon in the North

Saturn's northern hexagon is one of the most recognizable features in the solar system, a six-sided jet pattern that has persisted through decades of observation by ground telescopes, Voyager, and Cassini. Its stability is the point of comparison here.

The southern feature has 10 sides rather than six, has a documented history of only about three years, and is reported as changing rather than fixed. Those differences are why the team describes it as a new phenomenon developing on a familiar planet rather than a mirror image of the hexagon.

Mike Wong, a study co-author at the University of California, Berkeley, said the value of OPAL comes from repetition. Many of the program's findings, he noted, rest on years of accumulated data rather than any single observation.

Follow-Up Observations and the Open Questions

The authors are clear that this is a description, not an explanation. What drives the wave, how long it will last, and how it compares mechanically to the hexagon are all unresolved. The team says further study is needed from Hubble and the James Webb Space Telescope, along with analysis of computer models.

Two possibilities remain open. The decagon could settle into a long-lived, stable configuration resembling the northern hexagon, or it could continue to change and eventually break down. The team plans continued observation to find out which.

NASA has also raised a longer-term question about whether patterns like these on giant planets relate to atmospheric dynamics closer to home. That remains an open research question, not a finding. Nothing in this study establishes a link to weather on Earth.

For readers who want to follow the story, the practical steps are modest. Saturn is well placed for backyard telescopes through the autumn, and NASA publishes a monthly skywatching guide with current viewing conditions. The polar detail described here is not visible in amateur equipment, but the ground-based image archive that started this discovery accepts contributions from experienced observers.

Nature World News will report on further Hubble and Webb observations as the research team releases them.

What Readers Want to Know

What did astronomers actually find?

A 10-sided atmospheric wave, called a decagon, encircling Saturn's south pole. It is the first large, regular-sided jet pattern observed in the planet's southern hemisphere, and Hubble data trace its presence back to 2023.

Is this the same as Saturn's famous hexagon?

No. The hexagon sits at the north pole, has six sides, and has appeared in every observation for more than 40 years. The southern decagon has 10 sides, a documented history of about three years, and appears to be strengthening rather than holding steady.

Does this tell us anything about weather on Earth?

Not at this stage. NASA has said future work could explore whether giant planet atmospheric patterns relate to dynamics seen on Earth, but that is an open question. This study does not establish any such connection.

How confident are scientists in the finding?

The result is peer-reviewed and published in Science Advances, and it draws on multiple years of Hubble imaging plus independent ground-based observations. What remains uncertain is the cause of the wave, its lifespan, and how it compares mechanically to the hexagon.

Can this be seen with a backyard telescope?

No. The polar detail requires the resolution of a space telescope. Saturn itself is visible in amateur equipment, and NASA publishes monthly skywatching guidance for current viewing conditions.

What happens next?

The research team plans continued Hubble observations, with additional data expected from the James Webb Space Telescope and from computer modeling, to determine whether the decagon stabilizes or continues to evolve.