Possible Signs of Water and Differentiation in a Rocky Exoplanetary Body

TL;DR

This study presents evidence of water and differentiation in a rocky exoplanetary body orbiting a white dwarf, based on spectroscopic analysis of debris and stellar contamination.

Contribution

It provides the first indication of water and differentiation in a rocky exoplanetary body through combined infrared and spectroscopic observations.

Findings

Detection of water-related oxygen excess in debris

Evidence of differentiated planetary material

Presence of metal composition suggesting planetary layering

Abstract

Spitzer observations reveal the presence of warm debris from a tidally destroyed rocky and possibly icy planetary body orbiting the white dwarf GD 61. Ultraviolet and optical spectroscopy of the metal-contaminated stellar photosphere reveal traces of hydrogen, oxygen, magnesium, silicon, iron, and calcium. The nominal ratios of these elements indicate an excess of oxygen relative to that expected from rock-forming metal oxides, and thus it is possible that water was accreted together with the terrestrial-like debris. Iron is found to be deficient relative to magnesium and silicon, suggesting the material may have originated as the outer layers of a differentiated parent body, as is widely accepted for the Moon.