# Expected Planets in Globular Clusters

## TL;DR

This paper discusses the low probability of detecting planets in globular clusters due to metallicity effects, suggesting planets may still exist but are difficult to observe, impacting stellar evolution understanding.

## Contribution

It introduces a metallicity-dependent parameter Ie to analyze planetary system properties and discusses implications for planetary presence and stellar evolution in globular clusters.

## Key findings

- Low detection probability of planets in globular clusters.
- Planetary systems in low metallicity stars tend to have higher Ie values.
- Implications for stellar evolution and white dwarf formation.

## Abstract

We argue that all transient searches for planets in globular clusters have a very low detection probability. Planets of low metallicity stars typically do not reside at small orbital separations. The dependance of planetary system properties on metallicity is clearly seen when the quantity Ie=Mp[a(1-e)]^2 is considered; Mp, a, e, are the planet mass, semi-major axis, and eccentricity, respectively. In high metallicity systems there is a concentration of systems at high and low values of Ie, with a low-populated gap near Ie~0.3 M_J AU^2, where M_J is Jupiter's mass. In low metallicity systems the concentration is only at the higher range of I_e, with a tail to low values of Ie. Therefore, it is still possible that planets exist around main sequence stars in globular clusters, although at small numbers because of the low metallicity, and at orbital periods of >~10 days. We discuss the implications of our conclusions on the role that companions can play in the evolution of their parent stars in globular clusters, e.g., influencing the distribution of horizontal branch stars on the Hertzsprung-Russell diagram of some globular clusters, and in forming low mass white dwarfs.