Saturn's rings are among the most magnificent wonders of the solar system - with a diameter of about 280.000 kilometers - as they stretch around the gas giant. But smaller celestial bodies in the solar system also have their own rings, which, although more modest in size, are just as fascinating.
Scientists have now observed for the first time the formation and evolution of a ring system consisting of four rings and diffuse material around a small icy body called Chiron, which orbits the Sun in the space between Saturn and Uranus, Reuters reports.
Chiron belongs to a class of objects known as centaurs, which inhabit the outer reaches of the Solar System, between Jupiter and Neptune, exhibiting characteristics of both asteroids and comets. Officially designated (2060) Chiron, it is about 200 kilometers in diameter and takes approximately 50 years to orbit the Sun. Centaurs are composed primarily of rock, water ice, and complex organic compounds.
Astronomers have been observing Chiron intermittently since its discovery in 1977 and have long known that it is surrounded by material. In the new study, scientists used a telescope at the Pico dos Dias Observatory in Brazil in 2023 to obtain the best data yet, comparing it with observations from 2011, 2018 and 2022.
The results showed that Chiron is surrounded by well-defined rings - three denser rings are approximately 273, 325 and 438 kilometers from its center, while a fourth, newly discovered ring is located as much as 1.400 kilometers from the core. This outer layer is unusually distant and requires additional observations to confirm its stability. The three inner rings are located within a disk of dust that surrounds them, Reuters reports.
By comparing data from different years, the researchers found significant changes in the ring system - clear evidence that they are changing evolutionarily in real time, said Cristian Luciano Pereira, a postdoctoral researcher at the National Observatory in Brazil and lead author of the study published in the Astrophysical Journal Letters.
"This gives us a rare insight into how such structures form and change," Pereira said.
He added that Chiron's rings are likely composed mostly of water ice mixed with tiny rock particles, similar to Saturn's. Solid water may play a key role in the stability of ring systems by allowing particles to remain separated, rather than coalescing into a new moon.
Chiron occasionally exhibits comet-like behavior, ejecting gas and dust into space. In 1993, it even had a short tail of material, like a comet.
Scientists believe the rings may have been formed from the debris of a collision - possibly destroying Chiron's smaller moon - or from the impact of space debris, or perhaps from material ejected by Chiron itself, or a combination of all of these processes.
"It is a system in development that will help us understand the dynamic mechanisms of the formation of rings and satellites around smaller bodies, with potential implications for other disks in the universe," said astronomer Braga Ribas of the Federal University of Technology of Paraná and the Interinstitutional Laboratory of e-Astronomy in Brazil.
All four outer planets of the solar system - Jupiter, Saturn, Uranus and Neptune - have rings, with Saturn's being the largest and most striking. However, since 2014, astronomers have discovered that some smaller bodies also have ring systems. Chiron is now the fourth such body, joining the centaur Charicles and the two icy worlds beyond Neptune - Haumea and Quasar.
"This diversity reminds us that ring formation is not a privilege of large planets. It is a universal process that can occur wherever the right physical conditions exist," Pereira said.
A team of researchers from Brazil, France, and Spain used the star-obscuration method to observe Chiron's rings. They observed the moment when Chiron passed in front of a distant star, temporarily blocking its light. By measuring how the light dimmed from different locations on Earth, they were able to accurately reconstruct the environment around Chiron.
"We can reconstruct the shape and surroundings of the object with an accuracy of up to a few kilometers," Pereira concluded.
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