JWST finds Chariklo's rings changing in opposite directions

Overview

Updated 1 hour ago

Chariklo is a small body orbiting between Saturn and Uranus, and it hosts two narrow rings discovered in 2013. New James Webb Space Telescope observations show those rings are not stable: the inner ring has grown denser while the outer ring has faded, all within a few years.

The finding, published in Science Advances on September 15, challenges a decade-old assumption that rings around small bodies persist for eons. Astronomers now face an open question: what is reshaping Chariklo's rings, and are other small-body ring systems equally short-lived?

Why it matters

Astronomers assumed rings around small bodies were stable for eons. JWST shows Chariklo's changed within years, forcing a rethink of ring formation.

Questions about this story

Free account needed to ask — your question is kept and asked for you right after sign-up. Answers are public.

No questions yet — be the first to ask.

Key Indicators

Rings showing opposite opacity changes

Inner ring grew more opaque while outer ring faded in JWST data

2.5 km/s

Chariklo's relative speed during JWST occultation

Unusually slow relative motion gave sharper spatial detail than ground observations

10+

Years of ground observations compared to JWST data

Decade of stellar occultation measurements showed the inner ring gained opacity, outer ring lost it

Voices

Curated perspectives — historical figures and your fellow readers.

Ever wondered what historical figures would say about today's headlines?

People Involved

Pablo Santos-Sanz

Research scientist at Institute of Astrophysics of Andalusia (IAA-CSIC), lead author of the Chariklo ring study

Leading follow-up occultation campaigns

Organizations Involved

Institute of Astrophysics of Andalusia (IAA-CSIC)

Research institute within Spain's CSIC national research council

Leads the Chariklo ring research program

Spanish research institute that planned and executed the JWST occultation observation and analysis.

James Webb Space Telescope

Space telescope operated by NASA, ESA, and CSA

Instrument used for the 2022 Chariklo occultation observation

Flagship infrared space observatory whose fine resolution enabled the Chariklo occultation measurements.

Science Advances

Peer-reviewed scientific journal (AAAS)

Published the Chariklo ring evolution study in September 2026

AAAS open-access journal covering all fields of research.

Timeline

June 2013 September 2026

3 events Latest: Yesterday

September 2026
Chariklo ring changes published
Latest Publication

Science Advances study: inner ring more opaque, outer fainter versus a decade of ground data.
Yesterday
October 2022
JWST observes Chariklo occultation
Observation

JWST observes Chariklo's occultation, first planned for the telescope; relative speed just 2.5 km/s.
October 18th, 2022
June 2013
Chariklo's rings discovered
Discovery

Astronomers find two narrow rings around Chariklo during a stellar occultation in South America.
June 3rd, 2013

Scenarios

Follow-up occultations show Chariklo's rings are still changing

Possible Resolves by End of 2027

Discussed by: Study team at IAA-CSIC; astronomers plan additional targeted occultation measurements from space and ground

New occultation observations from JWST and ground telescopes would show the inner ring continuing to gain opacity and the outer ring losing more. That would point to real mass redistribution, possibly from a collision, a resonance with one of Chariklo's small moons, or gravitational sculpting by the body's irregular shape. The study authors note the physical origin remains unconfirmed.

Wavelength effects explain the apparent changes

Possible Resolves by End of 2027

Discussed by: Study authors, who note JWST used near-infrared filters while ground data used visible light

The rings' grains might scatter near-infrared and visible light differently, especially if their composition and size vary. If so, the apparent opacity shift reflects the different filters, not a change in ring mass. Follow-up observations at matching wavelengths would show the rings consistent with older measurements, meaning Chariklo's rings are as stable as assumed.

Both real change and wavelength effects are at play

Uncertain Resolves by End of 2028

Discussed by: Study authors, who said the scenarios are not mutually exclusive

The JWST signal could combine genuine ring evolution with wavelength-dependent opacity. Separating the two would need coordinated observations at multiple wavelengths over several years, tracking whether the inner ring keeps densifying and the outer ring keeps fading while filter effects are controlled. This would leave the mystery half-solved until enough epochs accumulate.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

March 1977

Discovery of Uranus's rings (1977)

Astronomers watching a star pass behind Uranus from NASA's Kuiper Airborne Observatory saw it flicker five times before and after the planet covered it, evidence of narrow rings. No one had predicted rings around Uranus, the first found beyond Saturn.

Then

Ring systems became a known feature of multiple planets, and stellar occultation became a standard tool for detecting them.

Now

Occultation-based searches later found rings around small bodies like Chiron and Chariklo.

Why this matters now

The same technique that discovered Chariklo's rings in 2013 is now exposing their rapid evolution.

2004-2017

Cassini measures Saturn's ring rain (2004-2017)

NASA's Cassini orbiter spent 13 years at Saturn and measured 'ring rain', material streaming from the rings into the planet. The rings turned out to be far younger than Saturn, likely no more than a few hundred million years old.

Then

Established that even Saturn's grand rings are not eternal structures.

Now

Built the view that ring systems can be transient on cosmic timescales.

Why this matters now

If the largest ring system is short-lived, Chariklo's rapid changes suggest small rings may be even more fleeting.

November 2011

Rings found around Chiron (2011)

Astronomers using stellar occultation found Chiron, a Centaur about 200 km across, also has rings or a shell of debris. It was the first hint that small bodies beyond the planets could host ring systems.

Then

Raised the possibility that rings are common around small bodies.

Now

Set the stage for the 2013 discovery of Chariklo's well-defined double ring.

Why this matters now

Chiron showed small bodies can have rings; Chariklo now shows such rings can change on timescales of a few years.