Astronomers utilizing the James Webb Space Telescope (JWST) have uncovered that the ring system surrounding Chariklo, a diminutive Centaur asteroid, exhibits unexpected variability. Orbiting the sun at approximately 17 times the Earth-sun distance, between Saturn and Uranus, this roughly 155-mile-wide body is part of a family of asteroids known for possessing ring systems, alongside its neighbor Chiron.
Although large planets such as Saturn, Uranus, Neptune, and Jupiter are famous for their ring structures, Chariklo’s existence proves that even small solar system bodies can sustain rings. Initial discoveries in 2013 identified two thick rings around the object, but new data indicates they are far more complex than originally understood.
Researchers from the Institute of Astrophysics of Andalusia (IAA-CSIC), led by Pablo Santos-Sanz, began observing Chariklo in October 2022. By employing stellar occultation—a method that tracks light dimming as an object passes before a star—they compared recent JWST data with occultation records from the previous decade.
“By comparing JWST observations with those obtained during other stellar occultations over the last decade, we discovered opposite changes in the two rings: while the inner ring shows significantly higher opacity, the outer ring shows lower opacity,” Santos-Sanz stated.
These findings suggest that the physics governing small bodies are more intricate than previously assumed. Scientists had long believed that rings around minor planets remained relatively stable. “Our results force us to rethink how they form, how they evolve, and what mechanisms maintain their stability,” Santos-Sanz noted. “The ability to detect these changes opens a new window for understanding the evolution of these systems and, possibly, that of other ring systems in the solar system.”
The cause of the opacity shifts remains unknown. However, the research also marks a significant technical achievement for the JWST and the European Space Agency’s Gaia mission.
“Achieving this required knowing with extraordinary precision the orbit of Chariklo, the position of the star, thanks to the European Space Agency’s Gaia mission, and the trajectory of JWST itself around the L2 Lagrange point,” explained Yücel Kilic of the IAA-CSIC. He added that station-keeping maneuvers are necessary to maintain the telescope’s orbit approximately 1 million miles beyond Earth.
During the studied occultation, Chariklo moved at roughly 5,600 miles per hour relative to the JWST. While swift by terrestrial standards, this speed is comparatively slow for solar system objects, allowing astronomers to resolve the rings in unprecedented detail. Direct imaging remains impossible due to the asteroid’s small size and distance, making occultation the primary tool for study.
The study was published on September 9 in the journal Science Advances.
Stellar occultation is amazing, but can we ever actually image these tiny rings directly? The precision required seems almost sci-fi.
Wait, the inner ring got denser while the outer one cleared out? That completely contradicts everything we thought about ring stability.
It’s fascinating how Chariklo’s rings are actively changing. I always assumed small bodies had static, dead systems like this.