A First Order Filter for the Detection of Potentially Habitable Exoplanets
Raka Dabhade, Jebraan Mudholkar, Siddhesh Durgude, Arpit Kottur
TL;DR
The paper addresses the challenge of prioritizing potentially habitable exoplanets amid thousands of candidates. It introduces a first-order, geometry-based filter using the dimensionless ratio $d/D_s$, calibrated by host spectral class to yield distinct Habitability Main Sequences for G, K, and M stars, with ideal values around $108$, $54$, and $27$, respectively. Using NASA Exoplanet Archive data, the authors demonstrate strong correlations between planets near these lines and higher Earth Similarity Index (ESI) values, validating the approach as an efficient screening tool and presenting an HR-diagram–like visualization for exoplanet habitability. While not a substitute for detailed atmospheric analysis, the method significantly accelerates the identification and prioritization of high-potential targets for follow-up with next-generation observatories such as JWST. This framework provides a practical, physics-mounded means to filter large datasets and guide observational strategies toward finding an Earth-like world.
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.