The external photoevaporation of planet-forming discs

TL;DR

This paper reviews how external photoevaporation by UV radiation from nearby massive stars influences the evolution of planet-forming discs, highlighting its significance in most star-forming regions and discussing future research directions.

Contribution

It provides a comprehensive review of the current theoretical and observational understanding of external photoevaporation and outlines key developments needed for future studies.

Findings

External photoevaporation is a dominant process in many star-forming regions.

Most discs are affected by UV radiation from massive stars, impacting planet formation.

Future research is needed to fully understand the role of external photoevaporation.

Abstract

Planet-forming disc evolution is not independent of the star formation and feedback process in giant molecular clouds. In particular, OB stars emit UV radiation that heats and disperses discs in a process called 'external photoevaporation'. This process is understood to be the dominant environmental influence acting on planet-forming discs in typical star forming regions. Our best studied discs are nearby, in sparse stellar groups where external photoevaporation is less effective. However the majority of discs are expected to reside in much stronger UV environments. Understanding external photoevaporation is therefore key to understanding how most discs evolve, and hence how most planets form. Here we review our theoretical and observational understanding of external photoevaporation. We also lay out key developments for the future to address existing unknowns and establish the full role of external photoevaporation in the disc evolution and planet formation process.