Astronomers make fresh discovery about icy celestial body after nearly 50 years

While Saturn's magnificent rings, spanning 175,000 miles (280,000 kilometres), are a familiar celestial marvel, scientists have now reported a groundbreaking discovery: the first observation of a ring system actively forming around a smaller icy body.

This nascent system, comprising four rings and diffuse material, encircles Chiron, an object orbiting the sun between Saturn and Uranus.

Chiron is a centaur, a class of bodies found between Jupiter and Neptune, displaying characteristics of both asteroids and comets.

Formally designated (2060) Chiron, this intriguing body measures approximately 200 kilometres (125 miles) in diameter and completes its solar orbit in about 50 years.

Centaurs are primarily composed of rock, water ice, and complex organic compounds, making this evolving ring system a unique subject of study.

Since its discovery in 1977, astronomers have observed Chiron off and on, and for years had known it was surrounded by material of some sort.

In the new research, scientists obtained their best data on Chiron in 2023 using a telescope at the Pico dos Dias Observatory in Brazil to go along with data from 2011, 2018 and 2022.

The researchers said these observations clearly showed that it is surrounded by well-defined rings - three dense ones about 170 miles (273 km), 202 miles (325 km) and 272 miles (438 km) from Chiron's center, and a fourth one, approximately 870 miles (1,400 km) from its center.

This outer feature, detected for the first time, lies unusually far from Chiron and, they said, requires further observations to confirm its stability as a ring.

The three inner rings are embedded within dust swirling around in a disk-like shape.

Comparing data from the various observations of Chiron, the researchers detected significant changes in the ring system, clear evidence that its rings are evolving in real time, according to Chrystian Luciano Pereira, a postdoctoral researcher at the National Observatory in Brazil and lead author of the study published in the Astrophysical Journal Letters.

"This provides a rare glimpse into how such structures originate and change," Pereira said.

Chiron's rings, Pereira added, are likely composed mainly of water ice mixed with small amounts of rocky material, like those of Saturn.

Water ice may play a key role in the stability of ring systems because its physical properties allow particles to remain separated instead of coalescing into a moon.

Chiron exhibits occasional comet-like activity - ejecting gas and dust into space. In 1993, Chiron even displayed a small tail of material, as comets do.

The researchers said its rings may be made of leftover material from a possible collision that destroyed a small moon of Chiron or from some other crashes of space debris, or could be from the stuff ejected from Chiron itself - or perhaps some combination of these factors.

"It is an evolving system that will help us understand the dynamical mechanisms governing the creation of rings and satellites around small bodies, with potential implications for various types of disk dynamics in the universe," said astronomer and study co-author Braga Ribas of the Federal University of Technology-Parana and the Interinstitutional Laboratory of e-Astronomy in Brazil.

All four of the solar system's big outer planets - Jupiter, Saturn, Uranus and Neptune - have rings, with Saturn's the largest.

But astronomers since 2014 have discovered that some of its smaller bodies have them, too. Chiron brings that number to four, joining fellow centaur Chariklo and two icy worlds beyond Neptune - Haumea and Quaoar.

"This diversity reminds us that ring formation is not exclusive to large planets. It's a universal process that can occur wherever the right physical conditions exist," Pereira said.

A method called stellar occultation was used by a team including Brazilian, French and Spanish researchers to observe the rings.

The researchers watched as Chiron passed in front of a distant star, temporarily blocking its light. By measuring how the starlight dims from different locations on Earth, they were able to discern the environment around Chiron.

"We can reconstruct the shape and environment around the object with kilometer-scale precision," Pereira said.