Thermal evolution of trans-Neptunian objects through observations of Centaurs with JWST

Abstract

We explore the surface properties of Centaurs 52872 Okyrhoe, 3253226 Thereus, 136204, 250112, and 310071 through their reflectance spectrum in the 0.6-5.3 µm range obtained using the JWST/NIRSpec spectrograph in the framework of the JWST GO-1 large program “Discovering the Surface Composition of the trans-Neptunian Objects, Icy Embryos for Planet Formation” (DiSCo-TNOs; PID 2418). We observe considerable diversity in their surface composition. Our analysis reveals two main categories among Centaurs that mirror similar findings in the Trans-Neptunian Objects: those with surfaces composed of refractory materials plus some degree of water ice, and those with a higher content of carbon-based materials. Our sample also includes two objects with a surface largely composed of refractory materials and little or no volatile material. Our compositional analysis suggests these objects have a high concentration of amorphous silicates, indicating surfaces composed of primitive, comet-like dust. As Centaurs travel closer to the Sun their surfaces tend to become less icy and more dominated by non-volatile materials due to the sublimation of volatiles. These findings suggest that similar groups in the solar system (comets, Jupiter Trojans, D-type asteroids, etc.) which are initially thought to have had icy compositions, may undergo comparable surface changes due to thermal processing.