# Planets In Young Massive Clusters: On the survivability of planets in young massive clusters and its implication of planet orbital architectures in globular clusters

## TL;DR

This study uses N-body simulations to explore the survivability of planets in young massive clusters, finding that wide-orbit planets are typically ejected within 10 million years, impacting the expected planet populations in globular clusters.

## Contribution

First detailed dynamical analysis of planet survivability in young massive clusters, linking initial orbital parameters to long-term stability and implications for globular cluster planet populations.

## Key findings

- Most wide-orbit planets are ejected within 10 Myr.
- Over 70% of close-in planets ($<5$ au) survive 100 Myr.
- Approximately 28.8% of ejected planets can escape the cluster.

## Abstract

As of August 2019, among the more than 4000 confirmed exoplanets, only one has been detected in a globular cluster (GC) M4. The scarce of exoplanet detections motivates us to employ direct $N$-body simulations to investigate the dynamical stability of planets in young massive clusters (YMCs), which are potentially the progenitors of GCs. In an $N=128{\rm k}$ cluster of virial radius 1.7 pc (comparable to Westerlund-1), our simulations show that most wide-orbit planets ($a\geq 20$~au) will be ejected within a timescale of 10 Myr. Interestingly, more than $70\%$ of planets with $a<5$~au survive in the 100 Myr simulations. Ignoring planet-planet scattering and tidal damping, the survivability at $t$ Myr as a function of initial semi-major axis $a_0$ in au in such a YMC can be described as $f_{\rm surv}(a_0, t)=-0.33 \log_{10}(a_0) \left(1 - e^{-0.0482t} \right) + 1$. Upon ejection, about $28.8\%$ of free-floating planets (FFPs) have sufficient speeds to escape from the host cluster at a crossing timescale. The other FFPs will remain bound to the cluster potential, but the subsequent dynamical evolution of the stellar system can result in the delayed ejection of FFPs from the host cluster. Although a full investigation of planet population in GCs requires extending the simulations to multi-Gyr, our results suggest that wide-orbit planets and free-floating planets are unlikely to be found in GCs.