JWST finds Chariklo’s rings are changing

Astronomers using the James Webb Space Telescope (JWST) have found that the ring system around the tiny solar system body Chariklo is more dynamic and complex than previously thought.
Chariklo, a 250-kilometre-wide member of the Centaur family, orbits the Sun between Saturn and Uranus at about 17 times the Earth-Sun distance. Despite its small size, it has two prominent rings, discovered in 2013.
Using JWST observations made in October 2022, researchers led by the Institute of Astrophysics of Andalusia (IAA-CSIC) found significant changes in the two rings.
The team used a technique known as stellar occultation, which measures a drop in a star’s light when an object passes in front of it.
By comparing the JWST data with observations from other stellar occultations over the past decade, researchers found that the inner ring has become significantly more opaque, while the outer ring has become less opaque.
The findings suggest that Chariklo’s rings are governed by more complex processes than previously believed. Scientists had thought that ring systems around small bodies were relatively stable.
“Our results force us to rethink how they form, how they evolve, and what mechanisms maintain their stability,” said Pablo Santos-Sanz of IAA-CSIC, who led the research.
The cause of the changes remains unknown. However, the ability to detect such variations could provide new insights into the formation and evolution of ring systems across the solar system.
The study also marks an important technical achievement for JWST. To make the observations possible, researchers needed highly precise information on Chariklo’s orbit, the position of the background star and the telescope’s trajectory around the L2 Lagrange point, about 1.5 million kilometres from Earth.
Data from the European Space Agency’s Gaia mission helped determine the star’s position with the precision required for the observations.
Chariklo is not the only small solar system body known to have rings. The Centaur Chiron also has a ring system, while the much larger planets Saturn, Uranus, Neptune and Jupiter possess their own ring systems.
The new findings suggest that rings may be more dynamic and widespread among small bodies than previously understood.