A First Order Filter for the Detection of Potentially Habitable Exoplanets

TL;DR

This paper introduces a simple geometric filter based on the orbital semi-major axis to stellar diameter ratio, tailored to stellar spectral class, to efficiently identify potentially habitable exoplanets from large datasets.

Contribution

It proposes a novel tiered ratio framework for habitability screening, dependent on stellar spectral class, enhancing target prioritization in exoplanet searches.

Findings

Strong correlation between the ratio and high Earth Similarity Index scores

Empirical ratios form 'Habitability Main Sequences' analogous to the Hertzsprung-Russell diagram

Framework enables rapid screening of large exoplanet datasets

Abstract

The search for potentially habitable exoplanets is a primary objective in modern astrophysics, yet the vast number of candidates discovered by missions like Kepler and TESS presents a significant challenge for detailed follow-up characterization. An efficient and reliable method for prioritizing the most promising targets is therefore essential. In this paper, we propose a novel first-order filter for identifying potentially habitable worlds based on a simple geometric ratio: the orbital semi-major axis to the stellar diameter ($d/D_s$). Using data from the NASA Exoplanet Archive, we demonstrate that the ideal value for this ratio is not constant, but is dependent on the host star's spectral class. We establish a tiered framework of ideal ratios, beginning with $\approx 108$ for G-type stars (anchored by the Earth-Sun system), and decreasing by a factor of two for K-type ($\approx 54$) and M-type ($\approx 27$) stars, respectively. Our analysis reveals a strong correlation, showing that exoplanets whose $d/D_s$ ratios are close to these empirically derived values consistently exhibit high Earth Similarity Index (ESI) scores. We propose that these tiered ratios represent "Habitability Main Sequences," analogous to the Hertzsprung-Russell diagram for stars, providing a valuable and straightforward tool for the astronomical community to rapidly screen large datasets and efficiently shortlist high-priority candidates for further investigation with next-generation observatories.