From Dust to Planets: A Novel Approach to Constrain Dust Growth and the Planet Forming Zone in Disks

Introduction

Exoplanets are frequent around Solar-like stars, as shown by large surveys. They are formed by the growth of dust and accumulation of gas contained in protoplanetary disks surrounding young stars.

Core-Accretion Scenario

To form planets, the classic Core-Accretion scenario is the main framework today, but it appears to be too slow given the short lifetimes of disks. Theoretical additions to Core-Accretion exist to speed it up. They all hypothesize that disks contain a massive, dense, and flat layer of pebbles in the midplane.

Objective 1: Observational Constraints

The validation of these scenarios will be impossible as long as the disk properties remain uncertain. The first objective of this project is to provide the first direct observational constraints (mass, vertical extent, radius) for this midplane pebble layer.

Methodology

Specifically, an original imaging programme for Edge-On disks will be combined with dedicated hydrodynamical models of vertical dust settling, taking into account dust evolution and dust-gas dynamics. This is very demanding.

Objective 2: Dust Shape and Growth Mechanisms

The second objective is to identify the shape of dust in young disks and pin down their growth mechanisms. This major advance is also crucial because the structure of dust governs the dust-gas dynamics (via collision and drag cross-sections) as well as the scattering properties needed to compare data and models.

Approach

To meet this goal, we will extract the scattering properties (phase function, polarization) from high-resolution images and use a unique micro-wave analogy experiment. Complex analog particles will be fabricated, measured, and compared with data to ultimately reveal the structure of dust in disks.

Final Objective: Understanding Dust Growth and Planet Assembly

All these results, combined in the final objective, will lead to a major leap towards a deep understanding of dust growth and early planet assembly in protoplanetary disks.

Potential Impact

Dust2Planets has the potential to overcome two long-standing obstacles in early planetesimal assembly:

1. How dust overcomes the radial-drift barrier
2. How dust overcomes the fragmentation barrier to form planetesimals.