In 2013, astronomers discovered a tiny object in our solar system with a ring like Saturn. Now, James Webb Space Telescope finds they are changing

In our solar system, several planets have their ring systems. Though Jupiter, Uranus, and Neptune have ring systems, only Saturn is famous for its ring. In 2013, however, another object of our solar system found to have the same.

The object, called Chariklo, is a small body orbiting between Saturn and Uranus. It is barely 250 kilometers in diameter and is located at nearly 17 times the Earth-Sun distance. Astronomers discovered the two dense rings around it in 2013. Now, observations from the James Webb Space Telescope have revealed that Chariklo’s faint, invisible ring system may not be as stable as scientists once thought.

Chariklo's rings are extremely faint, astronomers cannot simply photograph them in the way they can observe Saturn’s spectacular rings. researchers used a technique known as a stellar occultation. The method involves watching a distant star as Chariklo passes in front of it. As the object and its rings block some of the star’s light, scientists can use those tiny changes in brightness to determine the structure and properties of the rings.


The latest observations, led by the Institute of Astrophysics of Andalusia (IAA-CSIC) using the James Webb Space Telescope, have produced an unexpected result. When researchers compared the JWST observations with data from other stellar occultations conducted over the past decade, they found that the two rings appear to have changed in opposite ways.

The inner ring now appears significantly more opaque, while the outer ring appears less opaque.

“By comparing JWST observations with those obtained during other stellar occultations over the last decade, we discovered opposite changes in the two rings,” said Pablo Santos-Sanz, an IAA-CSIC researcher who led the study.

The finding, published in Science Advances, suggests that Chariklo’s rings may be a far more dynamic environment than scientists previously assumed. Until now, rings surrounding small bodies in the solar system were generally considered relatively stable over such short periods.

That makes Chariklo particularly intriguing. If its rings really are changing on timescales of only a few years, scientists may need to reconsider how these structures form, evolve and remain stable around small celestial bodies.

“Our results force us to rethink how they form, how they evolve, and what mechanisms maintain their stability,” Santos-Sanz said. The ability to detect such changes, he added, could provide a new way to study the evolution of ring systems across the solar system.

There is, however, an important caveat. Scientists have not yet determined exactly what is causing the apparent changes. They could represent genuine evolution of Chariklo’s rings, differences caused by observations made using different filters, or a combination of both effects.

The study brought together researchers from Spain, Brazil, France, Hungary and the United States, with the IAA-CSIC team leading the scientific planning, prediction of the JWST occultation, observations, data analysis, ring modeling and statistical work.

For an object only a fraction of the size of a planet, Chariklo is turning out to be surprisingly complicated. Its faint rings cannot easily be seen with conventional observations, yet the James Webb Space Telescope has now given astronomers a glimpse into a system that may be changing right before our eyes.