Confirmation and Keplerian motion of the gap-carving protoplanet HD 169142 b

TL;DR

This study re-detected a protoplanet candidate in the HD 169142 system, providing evidence of its Keplerian motion and associated spiral wake, supporting its classification as a forming planet within the protoplanetary disc.

Contribution

The paper presents the first multi-epoch detection and dynamical confirmation of a protoplanet in HD 169142, including its orbital motion and associated spiral wake, consistent with theoretical predictions.

Findings

Protoplanet detected at 37 au in the disc gap.

Object exhibits Keplerian motion across multiple epochs.

Spiral wake morphology matches hydrodynamical models.

Abstract

We present the re-detection of a compact source in the face-on protoplanetary disc surrounding HD 169142, using VLT/SPHERE data in YJH bands. The source is found at a separation of 0.''319 ($\sim$37 au) from the star. Three lines of evidence argue in favour of the signal tracing a protoplanet: (i) it is found in the annular gap separating the two bright rings of the disc, as predicted by theory; (ii) it is moving at the expected Keplerian velocity for an object at $\sim$37 au in the 2015, 2017 and 2019 datasets; (iii) we also detect a spiral-shaped signal whose morphology is consistent with the expected outer spiral wake triggered by a planet in the gap, based on dedicated hydrodynamical simulations of the system. The YJH colours we extracted for the object are consistent with tracing scattered starlight, suggesting that the protoplanet is enshrouded in a significant amount of dust, as expected for a circumplanetary disc or envelope surrounding a gap-clearing Jovian-mass protoplanet.