# Astrometric exoplanet detection with Gaia

**Authors:** Michael Perryman, Joel Hartman, Gáspár Bakos, Lennart Lindegren  
**arXiv:** [1411.1173](https://arxiv.org/abs/1411.1173)  
**Date:** 2014-11-05  
**Summary page:** https://www.summarizepaper.com/en/paper/1411.1173v1/

## Key points

- Michael Perryman, Joel Hartman, Gáspár Bakos, and Lennart Lindegren provide a revised assessment of the number of exoplanets that could be discovered by the Gaia astrometry mission.
- The authors extend previous studies to include a broader range of spectral types, distances, and magnitudes.
- Their assessment is based on a large representative sample of host stars from the TRILEGAL Galaxy population synthesis model, recent estimates of the exoplanet frequency distributions as a function of stellar type, and detailed simulations of Gaia observations using updated instrument performance and scanning laws.
- Two approaches are used to estimate detectable planetary systems: one based on the signal-to-noise ratio (S/N) of the astrometric signature per field crossing which allows for easy reproducibility and comparison with previous estimates; and a new metric based on orbit fitting to simulated satellite data that is more robust.
- Based on plausible assumptions about planet occurrences they find that some 21000 (+/-6000) high-mass (1-15M_J) long-period planets should be discovered out to distances of approximately 500pc for the nominal 5-year mission. This includes at least 1000-1500 planets around M dwarfs out to 100pc. For a 10-year mission duration this number rises to approximately 70000 (+/-20000).
- The authors also indicate some expected features of this exoplanet population. Among them are approximately 25-50 intermediate-period (P~2-3yr) transiting systems.
- Overall this study provides valuable insights into the potential discoveries that could be made by Gaia astrometry in terms of exoplanet detection across various spectral types and distances.

## Summary

In their paper titled "Astrometric exoplanet detection with Gaia," Michael Perryman, Joel Hartman, Gáspár Bakos, and Lennart Lindegren provide a revised assessment of the number of exoplanets that could be discovered by the Gaia astrometry mission. The authors extend previous studies to include a broader range of spectral types, distances, and magnitudes. Their assessment is based on a large representative sample of host stars from the TRILEGAL Galaxy population synthesis model, recent estimates of the exoplanet frequency distributions as a function of stellar type, and detailed simulations of Gaia observations using updated instrument performance and scanning laws. The authors use two approaches to estimate detectable planetary systems: one based on the signal-to-noise ratio (S/N) of the astrometric signature per field crossing which allows for easy reproducibility and comparison with previous estimates; and a new metric based on orbit fitting to simulated satellite data that is more robust. Based on plausible assumptions about planet occurrences they find that some 21000 (+/-6000) high-mass (1-15M_J) long-period planets should be discovered out to distances of approximately 500pc for the nominal 5-year mission. This includes at least 1000-1500 planets around M dwarfs out to 100pc. For a 10-year mission duration this number rises to approximately 70000 (+/-20000). The authors also indicate some expected features of this exoplanet population. Among them are approximately 25-50 intermediate-period (P~2-3yr) transiting systems. Overall this study provides valuable insights into the potential discoveries that could be made by Gaia astrometry in terms of exoplanet detection across various spectral types and distances.