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. However, it appears to be too slow given the short lifetimes of disks. Theoretical additions to Core-Accretion exist to speed it up.

Hypotheses on Disk Properties

These theories all hypothesize that disks contain a massive, dense, and flat layer of pebbles in the midplane. The validation of these scenarios will be impossible as long as the disk properties remain uncertain.

Objectives of the Project

First Objective

The first objective of this project is to provide the first direct observational constraints (mass, vertical extent, radius) for this midplane pebble layer. Specifically, an original imaging program 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.

Second Objective

The second objective is to identify the shape of dust in young disks and pin down their growth mechanisms. This major advance is 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.

Methodology

To meet this goal, we will:

1. Extract the scattering properties (phase function, polarization) from high-resolution images.
2. Use a unique micro-wave analogy experiment.
3. Fabricate, measure, and compare complex analog particles with data to ultimately reveal the structure of dust in disks.

Conclusion

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. Dust2Planets has the potential to overcome two long-standing obstacles in early planetesimal assembly: how dust overcomes the radial-drift and fragmentation barriers to form planetesimals.