# Abundant refractory sulfur in protoplanetary disks

## TL;DR

This study reveals that approximately 89% of sulfur in protoplanetary disks exists in refractory mineral form, mainly as sulfide minerals like FeS, which has implications for understanding planetary composition.

## Contribution

The paper introduces a novel method to determine refractory sulfur content in disks by analyzing stellar photospheres, revealing sulfur's dominant refractory form.

## Key findings

- 89% of sulfur is refractory in disks
- Sulfur mainly exists as sulfide minerals like FeS
- Refractory sulfur exceeds water ice contribution

## Abstract

Sulfur is one of the most abundant elements in the Universe, with important roles in astro-, geo-, and biochemistry. Its main reservoirs in planet-forming disks have previously eluded detection: gaseous molecules only account for $<1\,$\% of total elemental sulfur, with the rest likely in either ices or refractory minerals. Mechanisms such as giant planets can filter out dust from gas accreting onto disk-hosting stars. For stars above 1.4 solar masses, this leaves a chemical signature on the stellar photosphere that can be used to determine the fraction of each element that is locked in dust. Here, we present an application of this method to sulfur, zinc, and sodium. We analyse the accretion-contaminated photospheres of a sample of young stars and find $(89\pm8)\,$\% of elemental sulfur is in refractory form in their disks. The main carrier is much more refractory than water ice, consistent with sulfide minerals such as FeS.