Astronomers Observe Ring Formation Around Centaur Chiron – October 15, 2025 – Science
Astronomers have made significant observations detailing the dynamic ring system surrounding the centaur Chiron, a celestial body exhibiting characteristics of both asteroids and comets. The findings, published recently, provide a rare glimpse into the formation and evolution of planetary rings around smaller bodies.
Formally designated (2060) Chiron, the object is approximately 200 kilometers in diameter and completes an orbit around the Sun every 50 years. Composed primarily of rock, water ice, and complex organic compounds, Chiron has been the subject of astronomical study since its discovery in 1977. Observations have long indicated the presence of surrounding material, but recent data has revealed a more detailed picture.
Using data collected in 2011, 2018, 2022, and most recently in 2023 with a telescope at the Pico dos Dias Observatory in Brazópolis, Minas Gerais, Brazil, researchers identified four distinct rings around Chiron.Three dense rings are located at distances of 273 kilometers, 325 kilometers, and 438 kilometers from Chiron’s center. A fourth, more distant ring was detected at approximately 1,400 kilometers, though its long-term stability requires further observation. The three inner rings are embedded within swirling disks of dust.
Analysis of data from multiple observation periods revealed significant changes within the ring system, indicating that these structures are actively evolving. “This provides a rare glimpse into how these structures originate and change,” stated Chrystian Luciano pereira, a postdoctoral researcher at the National Observatory in Brazil and lead author of the study.
The rings are believed to be composed primarily of water ice, mixed with smaller amounts of rocky material, similar to the composition of Saturn’s rings. Water ice’s physical properties are thought to contribute to ring stability by preventing particles from coalescing into moons.
Chiron also exhibits occasional comet-like activity, ejecting gas and dust into space, and even displayed a small tail of material in 1993. The origin of the rings remains under examination, with potential sources including debris from a past collision with a small moon, impacts from space debris, or material ejected directly from Chiron itself – or a combination of these factors.
“It is indeed an evolving system that will help us understand the dynamic mechanisms that govern the creation of rings and satellites around small bodies, with possible implications for various types of disk dynamics in the Universe,” explained Braga Ribas, astronomer and study co-author from the Federal Technological Institute of Paraná (UTFPR) and the Interinstitutional e-Astronomy Laboratory (LIneA) in Brazil.
Chiron joins a growing list of smaller bodies observed to possess ring systems, including the centaur Chariklo, and the icy worlds Haumea and Quaoar. All four of the solar System’s large outer planets – Jupiter, Saturn, Uranus, and Neptune – also have rings, with Saturn’s being the most prominent. This discovery reinforces the idea that ring formation is not limited to large planets, but can occur under the right conditions throughout the universe.
