Reflected Light from Sand Grains in the Terrestrial Zone of a Protoplanetary Disk

TL;DR

This study reveals that millimeter-sized sand grains exist in the terrestrial zone of a young binary star's protoplanetary disk, with reflected light evidence indicating back scattering from the disk's far side.

Contribution

It provides new observational evidence of large dust grain growth and the scattering geometry in the inner regions of a protoplanetary disk around a young star.

Findings

Grains have grown to ~mm size in the terrestrial zone.

Reflected light is due to back scattering from the far side of the disk.

The disk's structure influences the observed scattering properties.

Abstract

We show that grains have grown to ~mm size (sand sized) or larger in the terrestrial zone (within ~3 AU) of the protoplanetary disk surrounding the 3 Myr old binary star KH 15D. We also argue that the reflected light in the system reaches us by back scattering off the far side of the same ring whose near side causes the obscuration.