Ringed Substructure and a Gap at 1 AU in the Nearest Protoplanetary Disk

TL;DR

High-resolution ALMA observations of the TW Hya disk reveal concentric ring-shaped substructures, including a narrow dark annulus at 1 AU, indicating possible planet formation sites and pressure maxima that influence disk evolution.

Contribution

This study provides the first high-resolution millimeter imaging of the nearest protoplanetary disk, revealing detailed substructures on AU scales and their potential links to planet formation processes.

Findings

Detection of concentric rings and gaps at 1-6 AU in TW Hya disk

Identification of a narrow dark annulus at 1 AU possibly related to planet interactions

Evidence of pressure maxima influencing dust concentration and disk evolution

Abstract

We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 870 micron continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli (1-6 AU) with modest contrasts (5-30%). We associate these features with concentrations of solids that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima. No significant non-axisymmetric structures are detected. Some of the observed features occur near temperatures that may be associated with the condensation fronts of major volatile species, but the relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the so-called zonal flows). Other features, particularly a narrow dark annulus located only 1 AU from the star, could indicate interactions between the disk and young planets. These data signal that ordered substructures on ~AU scales can be common, fundamental factors in disk evolution, and that high resolution microwave imaging can help characterize them during the epoch of planet formation.