Artistic representation of an active centaur like Chiron. The different colors in the coma indicate varying compositions of gas, ice, and dust. (Image Credit: William Gonzalez Sierra)
ORLANDO — In Greek mythology, a centaur is a creature that’s half-human, half-horse. Now, scientists have used NASA’s most powerful space telescope to study a different kind of hybrid lurking in our cosmic backyard – an object that’s both asteroid and comet, potentially offering new clues about our solar system’s earliest days.
Using the James Webb Space Telescope (JWST), researchers at the University of Central Florida have uncovered amazing insights about an object called Chiron, which inhabits the space between Jupiter and Neptune. What makes Chiron special is its dual nature – like other “centaurs” (named after those mythological hybrids), it displays characteristics of both asteroids and comets.
“What is unique about Chiron is that we can observe both the surface, where most of the ices can be found, and the coma, where we see gases that are originating from the surface or just below it,” explains Dr. Noemí Pinilla-Alonso, who led the research, in a university release.
The coma she refers to is a cloud-like envelope of dust and gas surrounding the object – think of it as Chiron’s personal atmosphere. This new study, published in the journal Astronomy & Astrophysics, revealed something never seen before: Chiron’s surface contains both carbon dioxide and carbon monoxide ice, while its coma contains these same materials in gas form, along with methane. This unique chemical makeup sets it apart from other centaurs discovered so far.
Why does this matter? Chiron and other objects like it are essentially time capsules from our solar system’s birth. While most things in our cosmic neighborhood have changed dramatically over billions of years, these distant objects have remained relatively unchanged, preserving information about our Solar System’s earliest days.
“These results are like nothing we’ve seen before,” says Charles Schambeau, an assistant scientist at UCF’s Florida Space Institute.
The fact that they could detect these gases so far from the Sun – where Chiron currently resides – is particularly remarkable, made possible only by the incredible capabilities of the James Webb Space Telescope.
First discovered in 1977, Chiron has always been considered unusual among its centaur peers. It sometimes acts like a comet, spewing gas and dust. It even has its own ring system and possibly a field of orbiting debris – features that make it particularly intriguing to scientists.
Chiron’s journey through our solar system is equally fascinating. It originally came from even farther out, beyond Neptune, and is currently just passing through its current location.
“After about 1 million years, centaurs like Chiron typically are ejected from the giant planets region, where they may end their lives as Jupiter Family comets or they may return to the TNOs region,” Pinilla-Alonso explains.
The research team plans to continue studying Chiron as it moves closer to Earth, hoping to better understand how its unique features respond to changes in sunlight and temperature. These future observations could help unlock more secrets about how our solar system formed and evolved over billions of years.
Paper Summary
Methodology
The research team used the Webb telescope’s Near-Infrared Spectrograph (NIRSpec) instrument to observe Chiron in July 2023. The instrument split Chiron’s reflected sunlight into its component colors, creating a detailed spectrum that reveals the chemical composition of both its surface and surrounding gas. The observations were made using three different wavelength ranges to provide complete coverage from 0.97 to 5.27 micrometers in the infrared portion of the spectrum. The team took multiple exposures and carefully processed the data to remove background noise and create clear spectral signatures of the various chemical components.
Key Results
The observations revealed multiple new discoveries: the first-ever detection of methane gas emission from a centaur at such distances, the presence of frozen carbon dioxide and various hydrocarbons on the surface, and evidence of chemical processing by radiation. The team also observed that the methane gas forms a distinct fan-shaped pattern extending outward from Chiron’s surface, suggesting a localized source of the emission.
Study Limitations
The study was limited to a single set of observations at one point in time, making it impossible to track how these emissions might change as Chiron moves along its orbit. Additionally, the observing mode wasn’t optimized for studying extended gas emissions, potentially limiting the detail in which the coma could be analyzed.
Discussion & Takeaways
The findings suggest that bodies in the outer solar system can maintain significant activity through mechanisms previously unknown. The presence of various processed chemicals indicates that Chiron’s surface has undergone substantial modification since its formation. This helps astronomers understand how similar bodies evolve over time and provides clues about conditions in the early solar system.
Funding & Disclosures
The research involved scientists from multiple institutions across several countries, including Spain, the United States, France, and Italy. The work was supported by various organizations, including NASA, CNRS (France), and multiple universities. The observations were part of the James Webb Space Telescope’s Guaranteed Time Observations Program 1273, led by Cornell University.
