Water ice in the debris disk around HD 181327

TL;DR

This study reports the first detection of water ice in a debris disk around HD 181327 using JWST, revealing a reservoir of large water-ice particles and dynamic processes affecting ice distribution.

Contribution

First direct detection of water ice in a debris disk around HD 181327, demonstrating the presence of large water-ice particles and their distribution via JWST spectroscopy.

Findings

Water ice detected at 3 μm with characteristic spectral features.

Water-ice mass fractions range from 0.1% to 14% at different distances.

Evidence of dynamic processes destroying and replenishing water ice.

Abstract

Debris disks are exoplanetary systems that contain planets, minor bodies (i.e., asteroids, Kuiper belt objects, comets, etc.), and micron-sized debris dust. Since water ice is the most common frozen volatile, it plays an essential role in the formation of planets and minor bodies. Although water ice has been commonly found in Kuiper belt objects and comets in the Solar System, no definitive evidence for water ice in debris disks has been obtained to date. Here, we report the discovery of water ice in the HD 181327 disk using the James Webb Space Telescope Near-Infrared Spectrograph. We detect the solid-state broad absorption feature of water ice at 3 $\mu$m and a distinct Fresnel peak feature at 3.1 $\mu$m, a characteristic of large water-ice particles. This implies the presence of a water-ice reservoir in the HD 181327 exoKuiper belt. Gradients of water-ice features at different stellocentric distances reveal a dynamic process of destroying and replenishing water ice in the disk, with estimated water-ice mass fractions ranging from 0.1% at ~85 au to 14% at ~113 au. It is highly plausible that the icy bodies that release water ice in HD 181327 could be the extra-solar counterparts of some of the Kuiper belt objects in our Solar System, supported by their spectral similarity.