JWST sees Chariklo's rings change over the past decade
Astronomers using the James Webb Space Telescope have found that one of Chariklo's two rings has grown denser while the other has almost vanished, a decade after the rings were discovered.
The finding follows the 2013 discovery of the rings. That year, Chariklo passed in front of a star and blinked twice on either side of the main event. The pattern revealed two narrow rings around an object barely 250 kilometers across. Pablo Santos-Sanz, an astronomer at the Instituto de Astrofísica de Andalucía in Granada, Spain, said the result was a surprise. Before that observation, astronomers had thought rings were something only giant planets had.
Since 2013, the question has been what such rings are made of and how long they can last. In a recent study, Santos-Sanz and his colleagues used the James Webb Space Telescope to watch Chariklo pass in front of a background star again. They found that one of its rings had grown denser and the other had almost vanished. The cause of the changes is not known exactly.
The observation relies on a stellar occultation. Santos-Sanz said researchers predict when a Solar System object passes in front of a star. The starlight dims for a moment, and the shape of that dip reveals the size, shape, and surroundings of the object that caused it. He said this is particularly challenging for minor bodies, and more challenging for distant minor bodies.
Editor's Summary The James Webb Space Telescope has observed Chariklo, a small body between Saturn and Uranus, and found that its two rings have changed since their 2013 discovery. One ring has become denser while the other has nearly disappeared. The reason for the change remains unknown, and the observation relied on watching Chariklo pass in front of a background star.