Scientists studying Saturn's newly identified 10-sided wave have a lead on what may have set it off. According to the UC Berkeley Space Sciences Laboratory, the decagon sits just south of a compact anticyclone vortex near 55 degrees south latitude. That vortex was first observed in 2023 and darkened sharply in 2025, just before the decagon emerged.

Study co-author Michael Wong of the laboratory suggested the vortex may have caused the initial disturbance, with the planet's balance of forces then sustaining the wave. "We really need more detailed simulations of its 3-D structure to know for sure," he said.

The timing gives readers a reason to look up. Saturn reaches opposition on Oct. 4, when it is closest to Earth for the year, at its brightest and visible all night. This year the planet's rings are tilted to show their southern face, and seasonal changes have brought Saturn's south pole, where the decagon formed, back into view from Earth.

A Storm Next Door and a Wave at 63 Degrees South

The new details sharpen the picture. When Hubble images from 2024 and 2025 were projected into a view looking down on the pole, the decagon appeared clearly at about 63 degrees south. The winds shaping it move at some 400 kilometers per hour (about 250 mph), according to the Berkeley release.

Observations through different filters show the wave has a three-dimensional structure extending through multiple layers of Saturn's atmosphere. The part visible in images sits in the upper troposphere. What aerosols give the wave its blue color, and how the structure continues deeper into the atmosphere, remain unknown.

"A few years ago, this feature wasn't there," Wong said, adding that the discovery shows why regular observation of the outer planets matters.

Lead author Agustín Sánchez-Lavega of the University of the Basque Country built a shallow-water model showing how a decagon could emerge in a turbulent fluid. That modeling demonstrates plausibility, not proof. Saturn's northern hexagon, discovered in 1980, has been reproduced in laboratory tanks of spinning liquid, yet scientists still debate why it forms on the planet itself.

Nature World News previously reported that researchers cannot yet explain why the decagon appeared now. The vortex does not settle that question, but it gives researchers a specific candidate to test.

A Brief Polygon Seen by Cassini in 2004

The decagon has a possible precursor in the record. In 2004, NASA's Cassini spacecraft imaged Saturn's entire southern hemisphere and found polygon-like perturbations in the band of jet currents near 60.5 degrees south. That feature lasted no more than a few days and was never seen again before Cassini's mission ended in 2017.

In 2024, images submitted to the Planetary Virtual Observatory Laboratory showed a subtle undulating band near the south pole, noticed by Sánchez-Lavega and amateur astronomers Trevor Barry and Jean-Paul Oger. Sánchez-Lavega then contacted the team behind Hubble's Outer Planet Atmospheres Legacy (OPAL) program to examine sharper images, which confirmed the feature's presence back to 2023. The peer-reviewed results appeared in Science Advances.

The OPAL program exists partly because of observation gaps. Principal investigator Amy Simon of NASA's Goddard Space Flight Center made the case for yearly Hubble surveys of Jupiter, Saturn, Uranus and Neptune after long gaps in outer-planet coverage, and Saturn observations under the program began in 2018, after Cassini's mission ended. NASA says the team will keep watching to see whether the decagon settles into a long-lived configuration like the northern hexagon or continues to evolve.

Saturn's Oct. 4 Opposition Offers the Year's Best View

At opposition, Earth passes between the Sun and Saturn. The planet rises around sunset and stays up all night, which makes this the middle of the best observing stretch of 2026. EarthSky reports that Saturn will be about 784 million miles (1.26 billion kilometers) from Earth at opposition, shining at magnitude 0.3 in front of the constellation Cetus. Its rings will be tilted about 7.5 degrees south relative to Earth, following the ring-plane crossing in March 2025, so they will look fairly narrow.

EarthSky adds that after opposition, Saturn will remain easy to see in the evening sky for the rest of 2026 before disappearing into the sunset glare in March 2027. Any small backyard telescope will show the rings, and nights from late August through mid-October offer excellent views.

Expectations matter here. Spotting the decagon at the eyepiece is not a realistic goal for most backyard observers. It was first noticed in images submitted by experienced amateur planetary imagers, and even Hubble's data needed polar projections to show the shape clearly. Casual observers can still enjoy the rings and the planet's banded disk on a clear, steady night, and nights a few days either side of Oct. 4 offer nearly the same view.

Ways Amateur Observers Can Contribute

Experienced planetary imagers can play a real role. The Planetary Virtual Observatory Laboratory accepts ground-based images of solar system planets from observers worldwide, and that archive is where the decagon was first noticed. Regular, well-documented images of Saturn's southern hemisphere could help researchers track whether the wave strengthens, drifts, or fades between Hubble visits.

For beginners, local astronomy clubs and public star parties are the easiest way to get a telescope view without buying equipment, and many clubs list public events through NASA's Night Sky Network.

Key unknowns remain. Researchers have not confirmed that the vortex caused the decagon, identified what makes it blue, or determined how deep it extends. They also cannot yet say how long it will last, which is why continued monitoring with Hubble, NASA's James Webb Space Telescope, computer models and ground-based observers matters.

The decagon now has a plausible trigger worth testing, and Saturn's best viewing nights of the year arrive in early October. Nature World News will report new Hubble, Webb or modeling results as the team releases them.

What Readers Want to Know

What new clue do scientists have about Saturn's decagon? A compact vortex near 55 degrees south darkened sharply in 2025, just before the decagon emerged, and researchers suspect it may have triggered the wave.

Has the cause been confirmed? No. Researchers say more detailed simulations of the wave's 3-D structure are needed before they can say whether the vortex set it off.

When is the best time to see Saturn this year? Around Oct. 4, when Saturn reaches opposition and is visible all night, though nearby nights offer nearly the same view.

Can I see the decagon through a backyard telescope? Most likely not by eye. It was first noticed in images from experienced amateur imagers, and Hubble data needed special projections to reveal it clearly.

How can amateur astronomers help? Experienced imagers can submit Saturn images to the Planetary Virtual Observatory Laboratory, which researchers use to track changes between Hubble observations.