James Webb Space Telescope Discovers Chariklo’s Rings are Changing

An international team led by the Instituto de Astrofísica de Andalucía (IAA-CSIC), with participation from the University of Oviedo, has detected for the first time changes in the two rings of Chariklo, a minor body orbiting between Saturn and Uranus. Published in Science Advances, the study relies on a stellar occultation planned and executed successfully using the James Webb Space Telescope (JWST) on October 18, 2022.

Stellar Occultation and High-Precision Orbital Mechanics

Observing Chariklo’s rings requires extreme technical precision because the structures are too narrow and distant to be imaged directly by any telescope. Researchers used a stellar occultation technique, measuring the brief drop in starlight as the body passed in front of a reference star. According to the IAA-CSIC, pulling this off required precise knowledge of Chariklo’s orbit, the star’s position via the European Space Agency’s Gaia mission, and the trajectory of the JWST around Lagrange point L2.

“Conseguirlo requirió conocer con una precisión extraordinaria la órbita de Chariklo, la posición de la estrella —gracias a la misión Gaia de la ESA— y la trayectoria del propio JWST alrededor del punto de Lagrange L2,” explains Yücel Kilic, an IAA-CSIC postdoctoral researcher and co-author of the study.

During the event, Chariklo moved relative to the JWST at a relative velocity of just 2.5 kilometers per second. This low relative velocity enabled unprecedented spatial resolution during the observation run.

Opposing Evolutionary Paths in a Minor Body’s Rings

By comparing the JWST occultation data with observations gathered over the past decade, the research team discovered that Chariklo’s two dense rings are evolving in opposite directions.

“La comparación de las observaciones del JWST con las obtenidas durante otras ocultaciones estelares a lo largo de la última década nos ha permitido descubrir cambios opuestos en los dos anillos: mientras el anillo interior muestra una opacidad significativamente mayor, el exterior presenta una opacidad menor,” notes Pablo Santos-Sanz, the IAA-CSIC researcher leading the work.

The inner ring has become significantly more opaque, while the outer ring shows a drop in opacity, indicating it could be progressively losing material. These findings challenge the assumption that ring systems around small Solar System bodies are stable, static structures. Instead, they appear to be highly dynamic environments governed by complex physical processes.

Composition and Unanswered Questions

Discovered in 2013, Chariklo was the first minor body found to host a ring system. Subsequent research involving Noemí Pinilla-Alonso from the University of Oviedo revealed that while Chariklo’s surface lacks water ice evidence, its two dense rings consist of a mixture of water ice, silicates, and organic compounds.

Photo: infobae.com

The physical origin behind the newly detected changes remains an open question. Researchers note the shifts could stem from actual temporal evolution within the rings, differences tied to observational filter choices, or a combination of both factors. The study opens new avenues for understanding how ring systems form, evolve, and maintain stability across the Solar System.