Free Astronomy Magazine January-February 2025

12 JANUARY-FEBRUARY 2025 ASTRO PUBLISHING N ASA’s James Webb Space Telescope observed Centaur 29P/Schwassmann- Wachmann 1, one of the most active objects in the outer solar system. Centaurs are “hybrid” objects in the sense that they share characteristics with trans-Neptunian objects from the Kuiper Belt reservoir and short-period comets. A team of scientists used Webb’s NIRSpec (Near-Infrared Spectrograph) instru- ment to study Centaur 29P. While data from previous radio-wavelength obser- vations of Centaur 29P showed a carbon monoxide (CO) gas jet pointed toward Earth, Webb parsed the jet’s composition in greater detail, and also detected multiple never-before-seen features of the centaur: two jets of carbon dioxide (CO 2 ) emanating in the north and south directions, and another jet of CO point- ing toward the north. Centaur 29P’s different CO and CO 2 abundances suggest that the body may be composed of different pieces that coalesced together dur- ing its formation. However, other scenarios to explain Centaur 29P’s outgassing activity are still being considered. [NASA, ESA, CSA, Leah Hustak (STScI), Sara Faggi (NASA-GSFC, American University)] in the outer solar system and evolved comets. A team of scientists recently used Webb’s NIRSpec (Near-Infrared Spectrograph) instrument to obtain data on Centaur 29P/Schwassmann- Wachmann 1 (29P for short), an ob- ject that is known for its highly active and quasi-periodic outbursts. It varies in intensity every six to eight weeks, making it one of the most active objects in the outer solar system. They discovered a new jet of carbon monoxide (CO) and previously unseen jets of carbon dioxide (CO 2 ) gas, which give new clues to the nature of the centaur’s nucleus. “Centaurs can be consid- ered as some of the leftovers of our planetary system’s formation. Be- cause they are stored at very cold temperatures, they preserve infor- mation about volatiles in the early stages of the solar system,” said Sara Faggi of NASA’s Goddard Space