Surface Composition of Centaurs: insights into the thermal evolution of TNOs

Abstract This study examines the 0.6 - 5.3 μm reflectance spectra obtained with JWST/NIRSpec spectrograph of five24 Centaurs: 52872 Okyrhoe (1998 SG35), 32532 Thereus (2001 PT13), 136204 (2003 WL7), 250112 (20027825 KY14), and 310071 (2010 KR59). Our analysis uncovers two distinct compositional groups within the Centaur26 population: water-rich and carbon-rich objects, echoing findings in the trans-Neptunian object (TNO) population.27 Significant variations in spectral-class distribution suggest differing surface compositions, especially in their28 upper layers. Centaurs, when passing through the giant planet region and experiencing heightened temperatures,29 exhibit less icy and more refractory surfaces than TNOs due to volatile species sublimation. Spectral models30 indicate a high abundance of amorphous silicates, signifying a substantial presence of “primitive” (or cometary-31 like) dust rich in such silicates. Similar populations (comets, Jupiter Trojans, Main Belt Comets, and D-type32 Asteroids) with comparable initial compositions are expected to exhibit spectral traits evolving due to thermal33 effects.