JWST Spectroscopy of a Blue Binary Cold Classical Kuiper Belt Object

TL;DR

This study uses JWST spectroscopy to analyze two binary Kuiper belt objects, revealing diverse surface compositions and suggesting a distinct formation environment for some water-ice-rich objects.

Contribution

First detailed JWST spectral analysis of binary Kuiper belt objects, identifying a subclass with unique surface features and implications for their formation history.

Findings

2001 XR254 shows features of carbon dioxide, carbon monoxide, and methanol ices.

2016 BP81 is a water-ice-rich, blue binary with identical spectral profiles.

A small subclass of water-ice-rich objects exhibits distinct spectral characteristics.

Abstract

We present observations of two binary systems within the cold classical region of the Kuiper belt$-$2001 XR254 and 2016 BP81$-$obtained with the JWST Near-Infrared Spectrograph. The measured reflectance spectrum of 2001 XR254 is characteristic of the red cold classicals, with strong features due to carbon dioxide, carbon monoxide, and methanol ices. In contrast, 2016 BP81 is a blue binary, with a water-ice-rich surface composition. The two components of the 2016 BP81 binary display identical spectral profiles, consistent with coeval formation from gravitational collapse. Through qualitative and quantitative comparisons of water-ice-rich Kuiper belt objects observed with JWST, we identify a small subclass, including 2016 BP81, that appears to differ in systematic ways from the rest of the population. The relatively deep carbon dioxide ice absorption bands and enhanced signatures of aliphatic organics suggest that objects within this subclass may have originated in a distinct formation environment from the other water-ice-rich Kuiper belt objects. The implications of our findings are discussed within the context of recent models of Kuiper belt formation and evolution.