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

Abstract: Several ground- and space-based searches have increased the number of known exoplanets to nearly 6000. While most are highly unlike our planet, the first rocky worlds in the Habitable Zone (HZ) provide the most intriguing targets for the search for life in the cosmos. As the detections increase, it is critical to probe the HZ as well as its limits empirically using known exoplanets. However, there is not yet a list of rocky worlds that observers can use to probe the limits of surface habitability. We analyze all known exoplanets and identify 67 rocky worlds in the empirical HZ and 38 in a narrower 3D-model HZ. We compare their demographics with the full catalog of exoplanets, analyze their characteristics, give HZ limits for each system, and prioritize targets for observation. We address another critical dimension to this exploration and compile missing stellar age estimates for these candidates. To probe the limits of habitability, we identify several transiting and non-transiting rocky planets that can provide constraints on the inner and outer edge of the HZ, explore how eccentricity influences habitability, and identify the oldest HZ worlds as well as exoplanets with similar flux to modern Earth's. The resulting list of rocky exoplanet targets in the HZ will allow observers to shape and optimize their search strategies with space- and ground-based telescopes -- such as the James Webb Space Telescope, the Extremely Large Telescope, the Habitable Worlds Observatory, and LIFE -- and to design new observing strategies and instruments to explore these intriguing worlds, addressing the question of the limits of surface habitability on exoplanets.