- Chariklo is a Centaur, an asteroid-like body that orbits the sun between Saturn and Uranus.
- Astronomers discovered two rings around Chriklo in 2013. It was the first body other than Jupiter, Saturn, Uranus and Neptune found to have rings.
- Now, a new study of observations by the Webb space telescope in 2022 shows that the rings are surprisingly dynamic, and changed over a period of only a few years.
The changing rings of Chariklo
In 2013, scientists discovered that Chariklo, a small rocky asteroid-like body called a Centaur between Saturn and Uranus, had rings. This was the first time that a body other than the planets Saturn, Uranus and Neptune, was found to have a ring system.
Later, on October 18, 2022, the James Webb Space Telescope conducted new observations of the two rings. Now, a new study led by the Institute of Astrophysics of Andalusia in Spain, shows that the rings have undergone changes in opacity over the past few years. The researchers said on September 9, 2026, that the inner ring showed greater opacity, while the outer ring showed less opacity.
Chariklo is only 155 miles (250 kilometers) in diameter. The discovery of rings around such a small body was unexpected. How did Chariklo get its rings? And why are they changing?
The new peer-reviewed findings were published in Science Advances on September 9, 2026.
Ring system changes in only a few years
The new observations by the Webb space telescope showed something unexpected. The ring system had changed in opacity over only a few years. Pablo Santos-Sanz, an IAA-CSIC researcher, led the new study. He said:
Comparing the JWST observations with those obtained during other stellar occultations over the last decade has allowed us to discover opposite changes in the two rings: while the inner ring shows a significantly greater opacity, the outer one presents a lower opacity.
The researchers used the stellar occultation technique, which measures the decrease in a star’s light when an object, such as a planet, passes in front of it.
Why did the opacity change? The researchers don’t know for sure, but the study suggests that the rings are unstable. Until now, scientists had thought that rings around such small bodies would be more stable. As Santos-Sanz explained:
Our results force us to rethink how they form, how they evolve and what mechanisms maintain their stability. The ability to detect these changes opens a new window for understanding the evolution of these systems and, possibly, that of other ring systems in the solar system.
1st stellar occultation for Webb
The observations were also another first for Webb. This was the telescope’s first stellar occultation predicted and planned in advance. Yücel Kilic, a postdoctoral researcher at IAA-CSIC, said:
Achieving this required knowing with extraordinary precision the orbit of Chariklo, the position of the star – thanks to the ESA’s Gaia mission – and the trajectory of the JWST itself around the L2 Lagrange Point, a region of space located about 1.5 million kilometers (0.9 million miles) from Earth in the opposite direction from the sun. The JWST orbits around this region following a trajectory that must be periodically corrected through maintenance maneuvers.
Bottom line: New observations by the James Webb Space Telescope show that the rings of Chariklo, a Centaur in the outer solar system, changed over a period of a few years.
Source: JWST stellar occultation reveals unexpected changes in Chariklo’s ring system
Via Institute of Astrophysics of Andalusia
Read more: Are Chariklo’s rings shaped by a tiny unseen moon?
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