The James Webb Space Telescope has unveiled peculiar characteristics of Chiron, a celestial body exhibiting both asteroid and comet traits. This discovery is expected to shed light on the formation processes of the Solar System.
Discovered in 1977, Chiron is recognized as the first known example of a centaur, which are small celestial objects that display features of both asteroids and comets. Its name is derived from mythological creatures that are half horse and half human.
Centaur bodies, numbering in the hundreds, are believed to originate from the cold regions beyond Neptune. As they migrate inward through the Solar System, sublimation of ice creates a gas halo or coma, reminiscent of comets.
According to Charles Schambeau from the University of Central Florida, Chiron stands out among these unusual bodies. He noted, “It has periods where it behaves like a comet, with material rings and possibly a debris field composed of small dust or rocks.”
Utilizing data from NASA’s James Webb Space Telescope, Schambeau and his team analyzed Chiron’s composition. Their findings, published in the peer-reviewed journal Astronomy & Astrophysics, reveal that the surface composition of Chiron’s ice differs significantly from other centaurs observed to date.
Chiron’s surface features carbon monoxide and carbon dioxide in solid form, while its coma contains carbon dioxide and methane gas. The presence of carbon monoxide in solid form on the surface, rather than in a gaseous state, is a surprising revelation.
Researchers believe that the gas is released through a complex process from various reservoirs within Chiron. Schambeau remarked, “These results are unlike anything we have seen before.”
For the first time, scientists have also detected water ice, ethane, and propane on a centaur. The team theorizes that the ethane and propane, which contain carbon, formed as a result of solar radiation interacting with surface methane and water.
More straightforward molecules like water and carbon dioxide are thought to have been incorporated into Chiron’s composition during the Solar System's formation 4.5 billion years ago.
Noemi Pinilla-Alonso, one of the authors of the study, stated that examining bodies like Chiron, which have remained relatively unchanged over time, can provide insights into the early periods of the Solar System.
Pinilla-Alonso also emphasized that current data do not support the existence of a standard centaur. “Every active centaur we observe with the James Webb Space Telescope has unique characteristics. There must be something explaining their different behaviors or a commonality we have yet to discover.”
As Chiron approaches the Sun over the next 20 years, it will become brighter, allowing for clearer observations. Scientists hope to answer questions regarding both centaurs and the history of the Solar System.