Astronomers using the James Webb Space Telescope have discovered that the ring system surrounding Chariklo, a tiny body belonging to the Centaur family of asteroids, is undergoing unexpected changes. Measuring roughly 155 miles or 250 kilometers wide, Chariklo orbits the sun between Saturn and Uranus at a distance of approximately 17 times the separation between Earth and the sun. Chariklo was initially discovered to possess two narrow rings during a 2013 stellar occultation event, overturning the previous assumption that ring systems were restricted exclusively to giant planets like Saturn, Uranus, Neptune, and Jupiter.
Webb Telescope Reveals Changing Rings on Distant Asteroid
Research published in Science Advances compares data collected by the space telescope with occultation records from previous years. A team led by researchers from the Institute of Astrophysics of Andalusia (IAA-CSIC) began observing the asteroid using the telescope in October 2022. By utilizing the stellar occultation technique—which measures the drop in light from a background star as an object passes in front of it—the team observed opposite shifts in Chariklo’s ring opacity over the past decade.
Shifting Opacity and Complex Ring Physics
According to team leader Pablo Santos-Sanz of the IAA-CSIC, comparisons with past occultations revealed that the inner ring shows significantly higher opacity, while the outer ring shows lower opacity. The Paris Observatory summarized the changes as an increase of about 50 percent in the inner ring’s opacity and a decrease of about 60 percent in the outer ring’s opacity compared to 2017 records.
These opposing shifts suggest that small solar system bodies experience much more complex physics than previously understood, challenging the long-held belief that small bodies maintain relatively stable ring systems. The exact cause of the changes remains a mystery, forcing scientists to rethink how these rings form, evolve, and maintain stability. Achieving these high-precision observations also relied on knowing the exact orbit of Chariklo, the position of the star using data from the European Space Agency’s Gaia mission, and the trajectory of the telescope itself around the L2 Lagrange point.
