This is a photo of Saturn captured by the NASA/ESA Hubble Space Telescope on October 22, 2023. The planet was about 1365 million kilometers away from Earth at the time of the photo. The Hubble Telescope’s advanced imaging capabilities enable us to see something called “ring spokes” on Saturn.
Ring spokes are temporary features that rotate along with the rings. They only last for about two or three rotations around Saturn. When new spokes are formed, they add to the existing pattern. The spokes were first photographed by NASA’s Voyager 2 in 1981, and since then, the Hubble Telescope has been observing them annually.
The Outer Planets Atmospheres Legacy (OPAL) program aims to monitor weather changes on all four gas-giant outer planets, including Saturn.
Hubble’s images reveal that the frequency of spoke apparitions is seasonal, with the pattern first appearing in 2021 but only on the left side of the rings. The number and contrast of the spokes vary with Saturn’s seasons, which last approximately seven years.
This year, the ephemeral structures are visible on both sides of the planet at the same time. Although they might look small compared to Saturn, they can be longer and wider than the diameter of Earth. The OPAL team believes that the spokes are most likely caused by interactions between Saturn’s magnetic field and the sun, generating electrostatic forces that lift dust or ice above the ring to form the spokes. However, after several decades, no theory perfectly explains this phenomenon.
By continuing observations with the Hubble Telescope, we may be able to solve this mystery one day. This image was created using Hubble data from proposal 16995 (A. Simon).