Exploring the impact of Stellar Multiplicity on planet formation Across Disc Evolution

Project Information

Stellar-MADE

Grant agreement ID: 101042275

DOI

10.3030/101042275

EC signature date 19 April 2022

Start date 1 October 2022

End date 30 September 2027

Funded under

• European Research Council (ERC)

Total cost

€ 1 246 258,00

EU contribution

€ 1 246 258,00

Coordinated by

UNIVERSITE GRENOBLE ALPES
France

Periodic Reporting for period 1 - Stellar-MADE (Exploring the impact of Stellar Multiplicity on planet formation Across Disc Evolution)

Reporting period: 2022-10-01 to 2025-03-31

Summary of the context and overall objectives of the project

In regions of active star formation, the protoplanetary discs around young stars act as planetary factories. Recent observing campaigns have shown that the majority of protostars belong to multiple stellar systems: the younger the stars, the higher the degree of multiplicity. Young discs are then strongly affected by stellar multiplicity, unavoidably modifying the way in which planets form. The detailed evolution of multiple systems with discs and planets however remains to be explored. Since most current models have been designed for single stars, there is an urgent need to extend these models to multiple stars. This will pave the way for a better understanding of the process of planet formation, at a more general level.
The Stellar-MADE project aims to provide a comprehensive view of disc dynamics and planet formation within multiple stellar systems. My team and I will thoroughly study multiples to:
1. Establish the formation channels of protoplanetary discs around young stellar objects;
2. Follow disc dynamics and grain growth in order to identify the regions of planetesimal formation;
3. Characterise planetary architectures and the resulting exoplanet population.
To achieve our goals we will perform hydrodynamical and N-body simulations, developing and adapting state-of-the-art codes (PHANTOM, MCFOST, REBOUND). Our calculations will include a broad range of physical processes: disc thermodynamics, radiative transfer, gravitational perturbations, aerodynamic friction, dust growth, and Mean-Motion Resonances. This will allow us to identify and quantify stellar multiplicity effects across evolution. My previous work on binary stars constitutes proof-of-concept that it is possible to coherently connect protoplanetary disc evolution to planetary architectures. Unveiling the effects of stellar multiplicity on planet formation will be a major breakthrough, which will enable us to interpret the whole exoplanetary population under a new and more realistic prism.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The Stellar-MADE project significantly advanced the understanding of protoplanetary disc dynamics in multiple stellar systems in the last 24 months. Following the work plan, the team developed cutting-edge hydrodynamical simulations and N-body models (Phantom, mcfost, Rebound) incorporating disc thermodynamics, dust growth, radiative transfer, and gravitational perturbations. In particular, within WP1, we developed the branch for multiple stellar systems for the hybrid code Phantom-mcfost considering discs in binaries during stellar outbursts (Poblete et al., in prep.). In WP2, the work carried out by A. Alaguero successfully connected disc observations and hydrodynamical models of a circumbinary disc in a triple stellar system (Alaguero et al., 2024). The work on WP3 is more recent but has already led to relevant publications in the field regarding planet stability in binary stars (Gianuzzi, Giuppone & Cuello, 2023; Cuello & Sucerquia, 2024; Sucerquia & Cuello 2025).

1. Organisation of a special session at the European Astronomical Society (EAS) annual meeting in Padova (Italy) in July 2024, chaired by the PI, at the European Astronomical Society (EAS) annual meeting in Padova (Italy) in July 2024.
2. Publication in A&A of the article led by A. Alaguero (Stellar-MADE PhD student), on a circumbinary disc in a triple stellar system.
3. Simulation tools for Phantom-mcfost developed and tested by P. Poblete (Stellar-MADE Postdoc), then shared with the community through the Phantom code public repository.
4. Invited reviews in Australia (2023) and Chile (2024) by the PI, plus several invited seminars (France, Italy, China, Germany) done by the team members.
5. Stellar-MADE’s outreach programs: Pint of Science 2023 in Grenoble, participation to a radio brodacast by A. Alaguero, and organisation of school activities at local schools.

Numerous collaborations with Monash (D.J. Price, C. Pinte), Milano (S. Ceppi, G. Lodato, E. Ragusa), ESO (E. Macías, C. Toci, M. Vioque), and Cambridge (C. Clarke, Á. Ribas). Results have been disseminated in 24 peer-reviewed articles, 13 featured talks at international conferences, and 7 invited review talks and seminars.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Stellar-MADE demonstrated how stellar multiplicity induces disc misalignment and structure, challenging the traditional single-star paradigm. The team quantified the dynamical and chemical evolution of (circumstellar, circumbinary, circumtriple) discs within multiple stellar systems. This is expected to have a major impact on the emergence and evolution of young planetary architectures in systems with more than one star.

These findings fundamentally shift our understanding of planet formation and offer new frameworks for interpreting exoplanet populations. The observations of V892 Tau and the dedicated models published in Alaguero et al. (2024) constitute a significant step forward in the field – as we simultaneously measured the impact of the inner stellar binary and the outer stellar companion on the circumbinary disc. This aspect highlights the project’s alignment with cutting-edge science. The complexity of modelling protoplanetary disc dynamics in the presence of several stars posed significant numerical challenges. Current models are primarily designed for single stellar systems, requiring substantial adaptation to account for the gravitational and thermodynamic interactions inherent in multiple systems. To overcome this, we focused our efforts in coupling the Lagrangian code Phantom (based on SPH) to state-of-the-art radiative transfer code mcfost.

Simulating these environments across diverse scales — ranging from a few au up to several hundreds of au — necessitated the integration of novel methods, which were developed within the team in collaboration with D. Price and C. Pinte (both at Monash University, Australia). Running these models while ensuring alignment with observational constraints was scientifically demanding. Furthermore, interpreting results in the context of the broad variety of disc structures was challenging, but very rewarding from the scientific perspective. Last, we are currently working on novel frameworks to model planetary architectures in multiple stellar systems and the upcoming exoplanet search in astronomical surveys. This follows closely the “high risk high gain” approach of the proposed research plan, with impactful results to be published soon in WP3.

The computational demands of high-resolution multi-scale simulations exceeded our initial projections. Therefore, we decided focus on a reduced number of highly relevant systems (such as FU Ori, GG Tau, V892 Tau) to maximise the scientific output of the novel tool Phantom-mcfost. This work is accompanied by an intense participation to ongoing observational campaigns of young multiple stellar objects (FAUST and exoALMA collaborations). This revised strategy efficiently reduces the amount hydrodynamical calculations, while being specifically designed to reproduce prototypical multiple stellar systems. Remarkably, it also reduces the overall carbon footprint of the project, without limiting its scientific impact.

Gallery of ALMA and VLT observations of circumbinary discs (Cuello, Alaguero & Poblete, 2025)

Gallery of ALMA and VLT observations of circumstellar discs (Cuello, Alaguero & Poblete, 2025)