Hubble Telescope Captures ‘Spokes’ in Saturn’s Rings; What Are These Mysterious Shadows?

Among the planets in the Solar System, Saturn is one of the iconic members due to its extensive ring system. These rings hold a secret that has mystified scientists for decades.

(Photo: Wikimedia Commons/ NASA)

Mysterious 'Ghostly' Shadows

On October 22, 2023, NASA/ESA Hubble Space Telescope captured a new image of Saturn from an astonishing 850 million miles (1.4 billion kilometers). The photo exposed an exciting detail of the gas giant with an analog-esque glow and a slightly grainy appearance. When the image of the thick white inner band on the rings is looked at carefully, shadowy objects appear like dirty fingerprints.

These spots were identified as the mysterious ring spokes around Saturn. They are nearly Earth-sized and appear to rotate along with the rings. Hubble captured this unusual feature under the Outer Planets Atmospheres Legacy (OPAL) program, which monitors the weather systems of Saturn and other gas giants.

This phenomenon is not new to the scientific community. It was first documented in 1981 by NASA's Voyager 2 and was observed again by the Cassini orbiter during its 13-year journey that ended in 2017.

The latest observations were particularly intriguing due to the clarity and detail provided by the ultra-sharp vision of the Hubble Telescope. This year's images show the elusive structures on both sides of the planet, which spin around the giant body.

Through the ongoing observations by the Hubble Telescope, astronomers hope to unlock the secrets of the mysterious spokes finally. As experts continue to gaze into the vastness of space, each discovery like this one deepens our understanding of the universe and reminds us of the infinite wonders it holds.

Weird Seasonal Spokes

The strange spokes remain visible only in two or three rotations around Saturn, after which they disappear. Because of this, capturing this phenomenon has been a difficult task historically.

This phenomenon was detected in OPAL data in 2021, where they were seen on the rings' morning (left) side. However, long-term monitoring shows variations in the number and contrast of the spokes. In the previous images captured by the Hubble telescope, the spokes appeared seasonally, with each season lasting for almost seven years on Saturn.

Simon said that as we head towards Saturn's equinox, we can expect maximum spoke activity with higher frequency and darker shadows that will appear over the next few years. This is because the tilt of the ringed planet at the equinox orients it and its rings in a way that solar winds are more able to collide forcefully with the planet's magnetic field, resulting in more pronounced spokes.

There are several theories regarding these mysterious shadows. According to OPAL program lead scientist Amy Simon, the leading theory suggests that the spokes are connected to the powerful magnetic field of Saturn, which also experiences solar interaction. Planetary scientists assume that such interactions could generate electrostatic forces that levitate dust or ice above the ring, resulting in the formation of spokes. However, no theory perfectly predicts their formation, even after decades of investigation.