Planet-Host Stars Across the Galaxy in the 2040s

TL;DR

This paper argues for a dedicated large-scale, high-resolution spectroscopic survey of planet-host stars across the Galaxy to determine how chemical composition, age, and Galactic birth environment influence planet formation and evolution. It outlines the necessary instrumentation, including a high-resolution ($R\sim40{,}000$) wide-field, high-multiplexing spectroscopic facility on a 10–12 m telescope, capable of surveying tens of thousands of hosts down to $G\sim21$–$22$ while providing homogeneous abundances and ages. By disentangling Galactic chemical evolution from planet formation signatures and exploring star-planet interactions and transmission spectroscopy, the approach aims to map planetary diversity across Galactic environments. The work emphasizes a strong need for NLTE modelling, comprehensive abundance diagnostics, and a robust non-host control sample to enable robust conclusions about planet formation processes.

Abstract

By the 2040s, the exoplanet field will have moved from the discovery of a few thousand planets to hundreds of thousands, thanks to Gaia DR5, TESS, PLATO, Roman, and their successors. At that stage, the key bottleneck will no longer be planet detection, but our ability to understand how planetary systems form, evolve, and diversify across different stellar and Galactic environments. To address this, we need a large-scale, high-resolution spectroscopic survey of planet-host stars, spanning a broad range of Galactic environments (thin and thick disks, bulge, halo, clusters, associations), and including a well-defined control sample of non-hosts. Such a survey must deliver homogeneous stellar parameters, detailed abundance determinations, ages, and kinematics for tens of thousands of hosts, extending to the faint magnitudes probed by future missions but are beyond the reach of existing and currently planned spectroscopic facilities.

Figures (1)

• Figure 1: Number of planets detected up to 2025 and a projection of the expected planets to be discovered in the future from J. Christiansen et al. (2025).