Astronomers utilizing the James Webb Space Telescope (JWST) have discovered that the ring system surrounding Chariklo, a tiny solar system body, is undergoing unexpected changes over timescales of just a few years. Orbiting the sun between Saturn and Uranus at roughly 17 times the distance between Earth and the sun, Chariklo is part of the Centaur family of asteroids and measures approximately 155 miles (250 kilometers) wide. Although ring systems were historically thought to be exclusive to giant planets like Jupiter, Saturn, Uranus, and Neptune, astronomers discovered in 2013 that Chariklo possesses two dense rings.
James Webb Space Telescope Reveals Dynamic Changes in Chariklo’s Rings
Now, observations led by researchers from the Institute of Astrophysics of Andalusia (IAA-CSIC) have revealed that these rings are stranger and more dynamic than initially believed. By comparing JWST data with observations gathered during stellar occultations over the past decade, the research team found opposite changes occurring simultaneously in the asteroid’s two rings.
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,
said team leader Pablo Santos-Sanz of the IAA-CSIC in a statement.
Challenging Assumptions About Small Body Ring Stability
The discovery suggests that tiny solar system bodies experience significantly more complex physics than previously understood. Prior to these findings, scientists believed that the ring systems surrounding small bodies remained relatively stable over time. The newly documented shifts challenge this long-held view and force researchers to reevaluate fundamental assumptions about how such rings form, evolve, and maintain their stability.
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.
While the exact cause of these ring opacity changes remains a mystery, the findings were published in the journal Science Advances.
A Technological Milestone for Space-Based Astronomy
In addition to providing astronomical insights, the research marked a major technical achievement. It was the first stellar occultation specifically predicted and planned for observation with the JWST, using a technique that measures the decrease in a star’s light when an object passes in front of it.
Successfully capturing the event required precise coordination across multiple astronomical initiatives. Team members had to account for the orbit of Chariklo, the exact position of the target star provided by the European Space Agency’s Gaia mission, and the trajectory of the JWST itself.
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, a region of space located about 1 million miles (1.5 million kilometers) beyond Earth, away from the sun,
explained team member Yücel Kilic of the IAA-CSIC. The telescope maintains its position around this point using periodic station-keeping maneuvers.
At the time of the observed occultation, Chariklo was traveling at roughly 5,600 miles per hour (2.5 kilometers per second) relative to the JWST. Because Chariklo is distant and its rings are extremely narrow, direct imaging via telescope is impossible. Instead, astronomers rely on stellar occultations to study the body indirectly, with the relatively low relative speed during this observation providing unprecedented spatial resolution of the ring structure.
