A small, dark body orbiting between Saturn and Uranus has surprised astronomers by changing its rings. In 2013, the object passed in front of a star and revealed two narrow rings, a discovery that showed rings were not the preserve of giant planets. Now a new look at the same body, known as Chariklo, shows one ring has grown denser while the other has nearly vanished.
The finding comes from a study led by Pablo Santos-Sanz, an astronomer at the Instituto de Astrofísica de Andalucía in Granada, Spain. The team used the James Webb Space Telescope to watch Chariklo pass in front of a background star again. The results, published in a recent paper, show the rings have changed in the space of a decade.
“It was a surprise,” Santos-Sanz said. “Ever since, the question has been what such rings are made of and how long they can last.”
The Blink That Changed Everything
The 2013 discovery came through a simple technique called occultation. Astronomers predicted when a Solar System object would pass in front of a star, then watched the starlight dim for a moment. The shape of that dip revealed the size, shape, and surroundings of the object that caused it.
This is particularly challenging for minor bodies, and more challenging for distant minor bodies. The target’s silhouette on the sky is minuscule, and knowing when it will cross a particular star requires very precise positioning data for both.
Still, in 2013, ground telescopes managed to discern Chariklo’s two rings, C1R and C2R. These sat 390 and 405 kilometers from its center and were only a few kilometers wide and about 7 kilometers apart.
What the New Data Shows
The recent study used the James Webb Space Telescope to repeat the measurement. The team watched Chariklo pass in front of a background star again, capturing the light curve once more.
They found one of the rings had grown denser. The other had almost vanished entirely. The exact cause remains unknown.
The Size of Chariklo
Chariklo is a small body, barely 250 kilometers across. That makes it a minor body by planetary standards. Its rings sit close to it.
| Feature | Chariklo |
|---|---|
| Diameter | ~250 kilometers |
| Ring distance | C1R: 390 km from center |
| Ring distance | C2R: 405 km from center |
| Rings visible in 2013 | Two |
| Rings visible now | One dense, one vanished |
The table shows the scale of the change. Chariklo is a tiny world with rings that exist in a narrow band around it. The 2013 rings were narrow and close, and the new data shows one has thickened while the other has disappeared.
The Occultation Method
The method relies on timing and precision. Astronomers must know the position of both the object and the star to within very high accuracy. Any error in the prediction can throw off the measurement.
The technique has a long history in astronomy. It has been used to measure the sizes of asteroids and comets. Chariklo’s rings were a notable detection on a minor body.
What the Rings Might Be Made Of
The composition of Chariklo’s rings remains unknown. The 2013 observations showed they existed, but they did not reveal what they were made of.
The recent study also did not resolve the composition question. It simply measured the light curves and noted the changes.
Why This Matters
The discovery of rings around Chariklo in 2013 changed what astronomers thought possible. Giant planets were not the only objects that could hold rings. Small, dark bodies could do it too.
The new data shows those rings are not permanent. They change over time. That tells us something about the forces acting on Chariklo and its environment.
What Comes Next
The study raises more questions than it answers. What caused one ring to grow denser? What caused the other to vanish? How long will the remaining ring last?
Santos-Sanz and his colleagues will likely continue observing Chariklo. Each future occultation will add another data point to the story of these rings.
The Surprise Factor
The 2013 discovery was unexpected. Astronomers did not think a small body could have rings. The finding changed that assumption overnight.
The new result continues that theme. It shows the rings are dynamic, not static. They change over time, and the telescope captured that change in a single decade.
What We Know So Far
The key facts are straightforward:
- Chariklo is a small body, barely 250 kilometers across.
- It orbits between Saturn and Uranus.
- In 2013, it passed in front of a star and revealed two narrow rings.
- The recent study used the James Webb Space Telescope to repeat the measurement.
- One ring grew denser.
- The other ring almost vanished.
- The cause remains unknown.
The finding is a reminder that the Solar System is full of surprises. A tiny world with rings was discovered in 2013, and now we see those rings changing before our eyes.
Source material: “Rings around a tiny body have changed over the past decade,” Ars Technica.
Get the Notebook.
The day's best stories and every fresh verdict, in plain English, in your inbox by seven. One email a day, no more.