Image of Centaur 39P taken during the NIRSpec O observation. Harrington Pinto et al. /arXiv, 2023
The James Webb Infrared Space Telescope is the first telescope to record the release of carbon dioxide by a centaur. The target of the observations was the active centaur 39P/Oterma; it is assumed that it is the release of carbon dioxide or carbon dioxide that provokes the activity of such objects. A preprint of the work is available at arXiv.org. Centaurs are unique small bodies in the Solar System that are considered a transition state for trans-Neptunian objects evolving into Jupiter-family comets. Their orbits are gravitationally perturbed by Jupiter and, to a lesser extent, Saturn, with perihelia greater than that of Jupiter and semimajor axes of the orbits less than those of Neptune.
To date, 42 active centaurs are known to be capable of exhibiting dust or gas comas; Their research not only gives ideas about how it works but also about the properties of the matter left after the formation of the solar system. A team of astronomers led by Olga Harrington Pinto of the University of Central Florida has published spectroscopic observations of Centaur 39P/Oterma using the NIRSpec instrument on the James Webb Telescope. The observations were made in the wavelength range of 0.6 to 5.3 micrometers on July 27, 2022, when the centaur was at a distance of 5.82 astronomical units from the Sun.
The researchers also analyzed observations of Centaurus from the ground-based telescope LDT (Lowell Discovery Telescope) and Gemini North in July and September 2022. 39P/Oterma is an active centaur discovered in 1943. Over the past 90 years, its orbit became similar first to the orbits of comets of the Jupiter family, then to the orbits of the centaurs, which happened due to interactions with Jupiter.
James Webb’s observations made it possible to detect carbon dioxide production on Centaur for the first time, occurring at a rate of 5.96 × 1023 molecules per second for 39P/Oterma. This is the lowest possible CO2 detection level for any comet or centaur. Carbon monoxide and water molecules were not detected, but spectroscopy suggests the presence of micrometer-sized water ice particles in the diffuse coma (if indeed present) of the centaur or on the surface of the It.