Webb Telescope Reveals Chariklo’s Rings Are Evolving, Not Static

Key points

• JWST observed Chariklo's rings in October 2022 using stellar occultation, a technique that measures the dimming of a background star as an object passes in front of it.
• Comparing JWST data with a decade of ground-based observations, researchers found that the inner ring (C1R) has increased in opacity, while the outer ring (C2R) has decreased in opacity.
• Chariklo, a centaur about 250 kilometers wide, orbits between Saturn and Uranus. Its rings were first discovered in 2013 and were previously thought to be stable.
• The cause of these changes is currently unknown, with possibilities including mass transfer, observational wavelength differences, or genuine temporal evolution.
• The findings suggest that rings around small bodies may evolve on shorter timescales than previously believed, prompting calls for further observations to determine if the changes are real or observational artifacts.

Background

Chariklo's rings were first discovered in 2013 through ground-based stellar occultations, marking the first time rings were found around a body smaller than a giant planet. Prior to this, rings were only known around large planets like Saturn, Uranus, Neptune, and Jupiter. The discovery of rings around Chariklo and other small bodies like Chiron and Quaoar challenged existing models of ring formation and stability. The recent JWST observations build on this by suggesting that these rings may not be static, but rather dynamic systems that can change over time.

How outlets are covering it

Space.com and Sky & Telescope both emphasize the surprise factor of the findings, noting that rings around small bodies were previously thought to be stable. Sky & Telescope highlights the role of amateur astronomers in providing the historical baseline data necessary for comparison. Martin Cid Magazine provides a more detailed analysis of the potential causes, including wavelength differences and mass transfer, and notes the importance of future observations to resolve these questions. UA.NEWS focuses on the technical aspects of the observation, such as the precision required and the speed of Chariklo's movement relative to the telescope. All sources agree that the cause of the changes is currently unknown and that further research is needed.

Why it matters

This discovery challenges existing models of ring formation and stability in the solar system. If rings around small bodies are indeed evolving on shorter timescales, it could imply that many more small bodies may host rings that are currently undetected. It also highlights the importance of JWST in studying small solar system objects and the value of long-term observational campaigns. The findings could lead to a better understanding of how rings form, evolve, and dissipate, which has implications for our understanding of the solar system's history and the dynamics of small bodies.

What to watch

The research team has identified future stellar occultations by Chariklo for which JWST pointings can be planned, with at least one candidate event in 2027. Observations at multiple near-infrared wavelengths will help determine if the opacity difference is due to grain-size dependence or actual changes in ring mass. A multi-epoch campaign could also determine if the inner ring's density continues to increase or has stabilized. These observations will help resolve whether the changes are real or observational artifacts and provide insights into the dynamics of small-body ring systems.