Chariklo, a small body only about 250 km across orbiting between Saturn and Uranus, has two rings that have changed over the past decade. First discovered in 2013 when it passed in front of a star, the rings were a surprise as astronomers thought only giant planets had such features. Recent observations using the James Webb Space Telescope (JWST) revealed that one ring, C1R, grew denser while the other, C2R, nearly vanished.

JWST observed the occultation on October 18, 2022, with its sightline skimming 7.4 km above Chariklo’s surface. The inner ring’s opacity increased from a historical average of 0.303 to 0.431, a change unlikely due to geometry alone after extensive simulations. The findings mark the first detection of a minor body’s rings in infrared bands beyond three micrometers, a range blocked by Earth’s atmosphere.

Pablo Santos-Sanz of the Instituto de Astrofísica de Andalucía led the study, noting the difficulty of predicting such events for distant minor bodies. Despite orbital challenges requiring JWST to be nudged at L2 and observations planned 14 days ahead, the team succeeded after weeks of recalibration. The results suggest real physical changes in Chariklo’s ring system, though the exact cause remains unknown.