Webb telescope detects unusual gas jets from Centaur 29P

Inspired by the half-human, half-horse creatures that are part of ancient Greek mythology, the field of astronomy has its own type of centaurs: distant objects orbiting the sun between Jupiter and Neptune. NASA’s James Webb Space Telescope has mapped the gases emitted by one of these objects, suggesting a varied composition and providing new insights into the formation and evolution of the solar system.

Centaurs are ancient trans-Neptunian objects that have been moved within Neptune’s orbit by subtle gravitational influences from the planets over the past several million years and could eventually become short-period comets. They are “hybrid” in the sense that they are in a transitional stage of their orbital evolution: many share characteristics both with trans-Neptunian objects (from the cold reservoir of the Kuiper belt) and with short-term comets. period, which are objects strongly altered by repeated close passages around the sun.

Since these small icy bodies are in an orbital transition phase, they have been the subject of various studies as scientists seek to understand their composition, the reasons for their outgassing activity (the loss of their ices located beneath the surface) and how they serve. as a link between the primordial icy bodies of the outer solar system and evolved comets.

A team of scientists recently used Webb’s Near-Infrared Spectrograph (NIRSpec) instrument to obtain data on Centaur 29P/Schwassmann-Wachmann 1 (29P for short), an object known for its very active, quasi-periodic explosions. Its intensity varies every six to eight weeks, making it one of the most active objects in the outer solar system. They discovered a new carbon monoxide (CO) jet and previously unseen carbon dioxide (CO) jets.₂) gaseous, which give new clues to the nature of the centaur core.

These results were published in Natural astronomy.

“Centaurs can be considered one of the remnants of the formation of our planetary system. Because they are stored at very cold temperatures, they preserve information about volatile substances in the early stages of the solar system,” he said. said Sara Faggi of NASA’s Goddard Space Flight Center. Greenbelt, Maryland and American University in Washington, DC, lead author of the study.

“Webb really opened the door to a resolution and sensitivity that impressed us: when we first saw the data, we were excited. We had never seen anything like it.”

Webb and the jets

The distant orbits of centaurs and resulting fading have prevented detailed observations in the past. Previous radio wavelength observation data from Centaur 29P showed a jet directed generally toward the sun (and Earth) composed of CO.

Webb detected this face-to-face jet and, using its large mirrors and infrared capabilities, also sensitively searched for many other chemicals, including water (H₂O) and CO₂. The latter is one of the main forms in which carbon is stored throughout the solar system. No clear indications of water vapor have been detected in 29P’s atmosphere, which may be related to the extremely cold temperatures present in this body.

The telescope’s unique imaging and spectral data revealed never-before-seen features: two CO jets₂ emanating in north and south directions, and another CO jet pointing north. This was the first definitive detection of CO₂ in Centaur 29P.

Based on the data collected by Webb, the team created a 3D model of the jets to understand their orientation and origin. They discovered through their modeling efforts that the jets were emitted from different regions of the centaur’s core, even though the core itself cannot be resolved by Webb. The angles of the jets suggest the possibility that the core may be an aggregate of distinct objects with different compositions; however, other scenarios cannot yet be ruled out.

“The fact that Centaur 29P exhibits such dramatic differences in CO and CO abundance₂ through its surface suggests that 29P could be made up of several pieces,” said Geronimo Villanueva, co-author of the study at NASA Goddard.

“Perhaps two pieces merged together and gave birth to this centaur, which is a mixture of very different bodies that followed distinct paths of formation. This challenges our ideas of how primordial objects are created and stored in the Kuiper belt.

Lingering unanswered questions (yet)

The reasons for the brightness bursts of Centaur 29P and the mechanisms behind its outgassing activity through CO and CO₂ jet aircraft, remain two major areas of interest that require further research.

In the case of comets, scientists know that their jets are often driven by the outgassing of water. However, due to their location, centaurs are too cold for water ice to sublimate, meaning that the nature of their outgassing activity differs from that of comets.

“We only had time to look at this object once, as a snapshot in time,” said study co-author Adam McKay at Appalachian State University in Boone, South Carolina. North.

“I would like to go back and observe Centaur 29P over a much longer period of time. Do the jets still have this orientation? Is there perhaps another carbon monoxide jet igniting at a different time in the rotation period? Looking at these jets, over time, would give us a much better idea of ​​what’s driving these explosions.”

The team hopes that as they deepen their understanding of Centaur 29P, they can apply the same techniques to other centaurs. By improving the astronomical community’s collective knowledge of centaurs, we can simultaneously improve our understanding of the formation and evolution of our solar system.