A distant comet is forming new rings while we watch in real time
Illustration of Chiron’s rings
Dan Durda
For the first time, astronomers are observing the formation of a ring system in real time. The rings in question encircle Chiron, a comet-like object that circles the sun between the orbits of Saturn and Uranus. Every time we look at Chiron, his rings look a little different.
Chiron is not the first small ring-shaped object we have observed: the asteroid Chariklo and the dwarf planets Haumea and Quaoar also have small ring systems. All of these rings were spotted using a method called stellar occultation, which involves waiting for the object to pass in front of a distant star and then creating a map of how the star’s light is blocked by orbiting material.
“There are maybe only around 20 objects that have been observed by stellar occultations, so observing four of them with rings is a high statistic,” says Bruno Sicardy of the Paris Observatory in France. “There are hundreds, if not thousands, of bodies, so there must be hundreds of ring systems.” He hopes we’ll find many more in the years to come.
Sicardy and his colleagues examined a stellar occultation that occurred in 2023 to determine the structure of the rings around Chiron. While previous observations revealed the likely presence of three rings, this new observation showed an additional disk of material enveloping those rings and extending farther from Chiron’s surface, as well as another ring even further away that has never been seen before.
“Nature shows us a ring in the forming phase, which is a great opportunity for us, because when we look at the rings of Saturn or Uranus, or even the rings of Chariklo, they basically always stay the same,” says Sicardy.
There are many different ways rings form, but observing their formation as it progresses could help us understand them much more deeply than we do today. “[This could] “This will provide a better understanding of the specific conditions that allow the formation, persistence or dissipation of rings and could ultimately explain why such systems are only found in cold and icy regions of the solar system,” explains Chrystian Pereira, a team member from the National Observatory of Brazil.
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