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

Abstract

The number of potentially habitable planets continues to increase, but we lack the time and resources to characterize all of them. With ∼30 known potentially habitable planets and an ever-growing number of candidate and confirmed planets, a robust statistical framework for prioritizing characterization of these planets is desirable. Using the ∼2 Gyr 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 Gyr. We perform this analysis on nine potentially habitable exoplanets with planetary radii <1.8 R ⊕ and/or planetary masses <10 M ⊕ around nine low-mass host stars (∼0.5–1.1 M ⊙) with measured stellar mass and metallicity, 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 2768 low-mass stars (0.5–1.3 M ⊙) in the TESS Continuous Viewing Zones.

Revising Properties of Planet–Host Binary Systems. II. Apparent Near-Earth-analog Planets in Binaries Are Often Sub-Neptunes*

“…1422.01 Small planets in or near the HZ are rare; in a search of the Berger et al (2020) catalog of revised Kepler planetary radii, there are 56 planets with R p < 1.8 R ⊕ that were classified as being in the HZ. Ware et al (2022) estimated that approximately 30 known Earth-analog planets fall in the HZ. There has been considerable effort exerted to calculate η ⊕ using the small sample of rocky HZ planets (Earth analogs hereafter), but measurements of η ⊕ have large errors (lack precision) and can substantially disagree between different works (lack accuracy).…”

“…There has been considerable effort exerted to calculate η ⊕ using the small sample of rocky HZ planets (Earth analogs hereafter), but measurements of η ⊕ have large errors (lack precision) and can substantially disagree between different works (lack accuracy). The cause of the lack of precision is the small sample of Earth analogs (e.g., Dressing & Charbonneau 2013;Gaidos 2013;Bryson et al 2021;Ware et al 2022), while the lack of agreement between different estimates is based in the various completeness corrections that different groups impose and the different samples and planet parameters they have used (e.g., Catanzarite & Shao 2011;Petigura et al 2013a;Foreman-Mackey et al 2014;Burke et al 2015;Dressing & Charbonneau 2015;Silburt et al 2015;Kunimoto & Matthews 2020;Bryson et al 2021).…”

The Maximal Distance of Detectable Isotropic Signals – Solving Fermis Paradox with Grimaldi’s Model

“…Kepler-442b is the only detected planet in the Kepler-442 system, which is 342 parasecs away from Earth, 1115.45 light years away. [29] [30] The stars closest to the Sun and thus most likely to be visited by space probes are Proxima Centauri, the binary star system Alpha Centauri A and B and Barnard's arrow star.…”