Astronomers have found that Chariklo, a tiny body orbiting between Saturn and Uranus, has rings that have changed significantly over the past decade. Observations by the James Webb Space Telescope suggest its inner ring has become denser while the outer ring may have almost disappeared, raising fresh questions about how such rings form and survive.

Chariklo is about 250 kilometres wide, with rings first detected in 2013 through stellar occultations. JWST observed the rings on 18 October 2022, when its sightline passed 7.4 kilometres above the surface, and measured the inner ring’s opacity at 0.431 compared with an earlier average of 0.303. Simulations indicated that an unusually dense patch was unlikely to explain the result, while the observation also showed the outer ring barely registering.