Detection of the Water Reservoir in a Forming Planetary System

TL;DR

This study detects cold water vapor in a young star's disk, indicating a substantial water ice reservoir and providing insights into water delivery and composition during planetary formation.

Contribution

First detection of water vapor in a protoplanetary disk using Herschel, revealing a large ice reservoir and differences in water composition compared to Solar System comets.

Findings

Water vapor detected around TW Hydrae star

Water reservoir equivalent to thousands of Earth Oceans

Ortho-to-para ratio suggests heterogeneous ice composition

Abstract

Icy bodies may have delivered the oceans to the early Earth, yet little is known about water in the ice-dominated regions of extra-solar planet-forming disks. The Heterodyne Instrument for the Far-Infrared on-board the Herschel Space Observatory has detected emission from both spin isomers of cold water vapor from the disk around the young star TW Hydrae. This water vapor likely originates from ice-coated solids near the disk surface hinting at a water ice reservoir equivalent to several thousand Earth Oceans in mass. The water's ortho-to-para ratio falls well below that of Solar System comets, suggesting that comets contain heterogeneous ice mixtures collected across the entire solar nebula during the early stages of planetary birth.