Probing the Limits of Habitability: A Catalog of Rocky Exoplanets in the Habitable Zone

Abstract

While most of the 6000 discovered exoplanets are highly unlike the Earth, the first rocky worlds in the Habitable Zone (HZ) provide intriguing targets for the search for life in the cosmos. As detections increase, it is critical to test the empirical HZ as well as its limits using known exoplanets. However, there is not yet a list of rocky worlds that observers can use to test the limits of surface habitability. We analysed data from Gaia DR3 and the NASA Exoplanet Archive (NEA) of all known exoplanets, identifying future targets to test limits of habitability through i) orbits near the edges of the HZ, ii) similar irradiation environments to modern Earth, and iii) large eccentricities. We prioritize targets for transmission observations, light curve measurements, and direct imaging, identify the oldest HZ rocky worlds based on the NEA and complementary literature data, and provide theoretical limits for the empirical HZ and a 3D-HZ for each system. Our analysis shows 45 rocky worlds in the empirical HZ and 24 in a narrower 3D-HZ. For context, we compare their demographics to those of the full catalog of exoplanets in the NEA. The resulting list of rocky exoplanet targets in the HZ will allow observers to shape and optimize search strategies with space- and ground-based telescopes -- such as the James Webb Space Telescope (JWST), Extremely Large Telescope (ELT), Habitable Worlds Observatory (HWO), and LIFE -- and design new observing strategies and instruments to explore these worlds, addressing the question of the limits of exoplanet surface habitability.