Uncovering a centaur’s tracks: Scientists examine unique asteroid-comet hybrid

Chiron belongs to the class of objects astronomers call the Centaurs. Centauri is a space object orbiting the Sun between Jupiter and Neptune. They resemble mythical creatures in that they are a hybrid, with characteristics of asteroids and comets.

Scientists at the University of Florida’s Florida Space Institute (FSI) recently led a team using the James Webb Space Telescope to discover for the first time that Chiron has a different surface chemistry than other centaurs. It has both carbon dioxide and carbon monoxide ice on its surface, as well as carbon dioxide and methane gases in the coma, which is surrounded by a cloud-like envelope of dust and gas.

The researchers’ findings were recently published in the journal Astronomy and Astrophysics.

UCF FSI Associate Scientist Noemí Pinilla-Alonso and Assistant Scientist Charles Schambeau, currently at the University of Oviedo, Spain, led the research. These new findings build on previous findings earlier this year by Pinilla-Alonso and colleagues that detected carbon monoxide and carbon dioxide ice for the first time on a trans-Neptunian object (TNO).

Pinilla-Alonso said these observations, combined with those of Chiron, are creating fundamental knowledge for understanding the formation of the solar system, because these objects have remained essentially unchanged since the formation of the solar system.

“Every small object in the solar system is telling us about how it traveled back in time, a period of time that we can no longer really observe,” she said. “But active centaurs tell us more. They are undergoing transformations driven by solar heating, and they provide unique opportunities to understand the surface and subsurface layers.”

Because Chiron has characteristics of both an asteroid and a comet, she said, it’s ideal for studying many of the processes that help understand them.

“What’s unique about Chiron is that we can observe both the surface, which is mostly icy, and also the coma, where we can see origins from the surface or from the surface,” Pinilla-Alonso said. The gas below. “TNOs don’t have this activity because they’re too far away and too cold. Asteroids don’t have this activity because they don’t have ice on them. Comets, on the other hand, show activity like centaurs, but they usually are observed close to the Sun, and their comas are very thick, complicating the interpretation of observations of surface ice. Understanding which gases are part of the coma and their different relationships with surface ice can aid discovery. Chemical properties, such as the thickness and porosity of the ice, its composition and how radiation affects it.

Finding these ices and gases on a distant object like Chiron, observed near its farthest point from the sun, is exciting because it could help understand the background of other centaurs and provide insights into the earliest days of the solar system, Chambeau said. Insights of the times.

“These results are something we’ve never seen before,” he said. “Detecting comas of gas around objects as far away from the sun as Chiron is very challenging, but JWST has achieved this goal. These detections enhance our understanding of Chiron’s internal composition and what happens when we observe Chiron understanding of how this material produces its unique behavior.

Chambeau specializes in centaurs, comets and other space objects. He analyzed the methane gas coma and determined that the detected outflowing gas was consistent with its origin in the surface areas most exposed to solar heat.

Chiron, first discovered in 1977, is much better characterized than most centaurs and is relatively unique, Schambeau said. He said the information from the new analysis will help scientists better understand the thermal physics of Chiron’s production of methane gas.

“It’s a weird thing compared to most other centaurs,” Chambeau said. “It behaved like a comet at certain times, with a ring of material around it, and possibly a debris field of small dust or rocky material orbiting it. So a lot has emerged about the properties of Chiron that allow for these unique behaviors. question.

The researchers concluded that the coexistence of molecules in different states adds another layer of interest to studying comets and centaurs. The study also highlights the presence of irradiation by-products of methane, carbon monoxide and carbon dioxide, which require further study and could help scientists shed further light on the unique processes that produced Chiron’s surface composition.

Pinilla-Alonso said Chiron originated in the outer core region of the Sea and Sky and has been orbiting the solar system since its birth. The orbits of Chiron and many other large non-planetary objects occasionally make close encounters with one of the giant planets, and the planet’s gravity changes the orbits of smaller objects, carrying them throughout the solar system and exposing them to many different environment, she said.

“We know that it has been expelled from the Neptuneian population and is only now passing through the giant planet region and will not stay there for long,” Pinilla-Alonso said. “About a million years from now, like Kai Centaurs like Dragon are often ejected from the giant planet region, where they may end their lives as Jupiter-family comets, or they may return to the TNO region.”

Pinilla-Alonso noted that JWST’s spectra show for the first time Chiron’s vast array of ices with varying volatilities and how they form, she said.

Some of these ices, such as methane, carbon dioxide, and water ice, may be original components that Chiron inherited from the pre-solar nebula. Other species, such as acetylene, propane, ethane and carbon oxides, may form on the surface as a result of reduction and oxidation processes, she said.

“Based on our latest JWST data, I’m not sure we have a standard Centaur,” Pinilla-Alonso said. “Every active centaur we observed with JWST showed some peculiarity. But they couldn’t all be outliers. There had to be something that explained why they seemed to behave differently, or there was something between them that we Common ground yet to be seen.

She said the analysis of Chiron’s gas and ice opens up new areas and opportunities for exciting research.

“We will follow up with the Chiron,” said Pinilla Alonso. “It will be much closer to us, and if we can study it at closer distances and better understand the amounts and properties of ice, silicates and organic matter, we will be able to better understand seasonal insolation changes and different lighting How the pattern affects will affect its behavior and ice storage.

The James Webb Space Telescope is the world’s premier space science observatory, unraveling the mysteries of the solar system, peering into distant worlds around other stars, and exploring the mysterious structure and origins of the universe. JWST is an international collaboration led by NASA and its partners the European Space Agency and the Canadian Space Agency.

Researchers’ qualifications

Pinilla-Alonso is a professor at FSI and joined UCF in 2015. Pinilla-Alonso also has a co-appointment as a research professor in the Department of Physics at the University of Central Florida and has led many international observing campaigns in support of NASA missions such as New Horizons, OSIRIS-Rex and Lucy. Pinilla-Alonso is Distinguished Professor at the Institute of Space Science and Technology of Asturias at the University of Oviedo. She received her PhD in astrophysics and planetary science from the University of La Laguna in Spain.

Schambeau, an assistant scientist, received his PhD in physics from UCF in 2018, with a concentration in planetary science. He subsequently joined FSI, where he expanded his work on comets and Centaurs as part of UCF’s Distinguished Postdoctoral Program.