# External photoevaporation of circumstellar disks constrains the timescale for planet formation

## TL;DR

This study uses simulations to show external photoevaporation significantly shortens disk lifetimes in star clusters, implying planet formation must occur rapidly within the first million years.

## Contribution

It provides new insights into how external photoevaporation influences disk evolution and constrains the timescale for planet formation in various stellar environments.

## Key findings

- 80% of disks destroyed within 2 Myr in dense regions
- Photoevaporation significantly impacts disk survival
- Supports rapid planet formation within 0.1-1 Myr

## Abstract

Planet-forming circumstellar disks are a fundamental part of the star formation process. Since stars form in a hierarchical fashion in groups of up to hundreds or thousands, the UV radiation environment that these disks are exposed to can vary in strength by at least six orders of magnitude. This radiation can limit the masses and sizes of the disks. Diversity in star forming environments can have long lasting effects in disk evolution and in the resulting planetary populations. We perform simulations to explore the evolution of circumstellar disks in young star clusters. We include viscous evolution, as well as the impact of dynamical encounters and external photoevaporation. We find that photoevaporation is an important process in destroying circumstellar disks: in regions of stellar density $\rho \sim 100 \mathrm{\ M}_\odot \mathrm{\ pc}^{-3}\mathrm{\ }$ around 80% of disks are destroyed before 2 Myr of cluster evolution. Our findings are in agreement with observed disk fractions in young star forming regions and support previous estimations that planet formation must start in timescales < 0.1 - 1 Myr.