Revised estimates of the frequency of Earth-like planets in the Kepler field

TL;DR

This paper refines the estimated frequency of Earth-like planets in the Kepler field by leveraging Gaia's precise parallax data to improve stellar and planetary radius measurements, informing future exoplanet searches.

Contribution

It provides an updated occurrence rate of Earth-sized planets in habitable zones using Gaia data, enhancing previous estimates with improved stellar radius accuracy.

Findings

Revised occurrence rate of Earth-like planets in the Kepler field.

Gaia parallax data significantly improves stellar radius estimates.

Updated estimates aid future exoplanet detection missions.

Abstract

The search for Earth-like planets around Sun-like stars and the evaluation of their occurrence rate is a major topic of research for the exoplanetary community. Two key characteristics in defining a planet as 'Earth-like' are having a radius between 1 and 1.75 times the Earth's radius and orbiting inside the host star's habitable zone; the measurement of the planet's radius and related error is however possible only via transit observations and is highly dependent on the precision of the host star's radius. A major improvement in the determination of stellar radius is represented by the unprecedented precision on parallax measurements provided by the Gaia astrometry satellite. We present a new estimate of the frequency of Earth-sized planets orbiting inside the host stars's habitable zones, obtained using Gaia measurements of parallax for solar-type stars hosting validated planets in the Kepler field as input for reassessing the values of planetary radius and incident stellar flux. This updated occurrence rate can usefully inform future observational efforts searching for Earth-like system in the Sun backyard using a variety of techniques such as the spectrograph ESPRESSO, the space observatory PLATO and the proposed astrometric satellite Theia.