The formation of planets by disc fragmentation

TL;DR

This paper explores how disc fragmentation influences the formation of planets, brown dwarfs, and stars, discussing conditions, outcomes, and observational evidence for different formation mechanisms.

Contribution

It provides a comprehensive discussion on the role of disc fragmentation in planet and star formation, highlighting potential observational signatures and formation pathways.

Findings

Most objects formed by fragmentation are brown dwarfs.

Planets may form via fragmentation if growth is halted or reversed.

Some observed exoplanets may have formed through disc fragmentation.

Abstract

I discuss the role that disc fragmentation plays in the formation of gas giant and terrestrial planets, and how this relates to the formation of brown dwarfs and low-mass stars, and ultimately to the process of star formation. Protostellar discs may fragment, if they are massive enough and can cool fast enough, but most of the objects that form by fragmentation are brown dwarfs. It may be possible that planets also form, if the mass growth of a proto-fragment is stopped (e.g. if this fragment is ejected from the disc), or suppressed and even reversed (e.g by tidal stripping). I will discuss if it is possible to distinguish whether a planet has formed by disc fragmentation or core accretion, and mention of a few examples of observed exoplanets that are suggestive of formation by disc fragmentation .