First Steps of Planet Formation Around Very Low Mass Stars and Brown Dwarfs

TL;DR

This paper discusses the early stages of planet formation around very low mass stars and brown dwarfs, highlighting recent observations of disk substructures and the challenges of forming giant planets in such environments.

Contribution

It reviews recent high-resolution ALMA observations of disks around brown dwarfs and VLMS, suggesting embedded giant planets as the cause of observed substructures and emphasizing the need for further deep observations.

Findings

Substructures observed in disks around BDs and VLMS suggest planet formation activity.

Giant planets are a likely cause of disk substructures, despite their rarity.

Forming giant planets around low-mass objects remains challenging for current models.

Abstract

Brown dwarfs and very low mass stars are a significant fraction of stars in our galaxy, and they are interesting laboratories to investigate planet formation in extreme conditions of low temperature and densities. In addition, the dust radial drift of particles is expected to be a more difficult barrier to overcome during the first steps of planet formation in these disks. ALMA high-angular resolution observations of few protoplanetary disks around BDs and VLMS have shown substructures as in the disks around Sun-like stars. Such observations suggest that giant planets embedded in the disks are the most likely origin of the observed substructures. However, this type of planets represent less than 2% of the confirmed exoplanets so far around all stars, and they are difficult to form by different core accretion models (either pebble or planetesimal accretion). Dedicated deep observations of disks around BDs and VLMS with ALMA and JWST will provide significant progress on understanding the main properties of these objects (e.g., disk size and mass), which is crucial for determining the physical mechanisms that rule the evolution of these disks and the effect on the potential planets that may form in these environments.