Continuous Habitable Zones: Using Bayesian Methods to Prioritize Characterization of Potentially Habitable Worlds

The number of potentially habitable planets continues to increase, but we lack the time and resources to characterize them. With dozens of potentially habitable worlds, over 2100 TESS candidate planets, and the first TESS habitable zone system recently confirmed (Rodriguez et al. 2020), a robust statistical framework for prioritizing characterization of these planets is desirable. Using the ~2 Gy it took life on Earth to make a detectable impact on the atmosphere as a benchmark, we use a Bayesian statistical method to determine the probability that a given radius around a star has been continuously habitable for 2 Gy. We perform this analysis on 9 potentially habitable exoplanets with planetary radii <1.8 R⊕ and/or masses <10 M⊕ around 9 low-mass (~0.5-1.1 M⊙) host stars with measured stellar mass and [Fe/H], as well as Venus, Earth, and Mars. Ages for the host stars are generated by the analysis. The technique is also used to provide age estimates for 2249 low-mass (0.5-1.3 M⊙) stars in the TESS Continuous Viewing Zones.