A Flexible Bayesian Framework for Assessing Habitability with Joint Observational and Model Constraints

Abstract

The catalog of stellar evolution tracks discussed in our previous work is meant to help characterize exoplanet host-stars of interest for follow-up observations with future missions like JWST. However, the utility of the catalog has been predicated on the assumption that we would precisely know the age of the particular host-star in question; in reality, it is unlikely that we will be able to accurately estimate the age of a given system. Stellar age is relatively straightforward to calculate for stellar clusters, but it is difficult to accurately measure the age of an individual star to high precision. Unfortunately, this is the kind of information we should consider as we attempt to constrain the long-term habitability potential of a given planetary system of interest. This is ultimately why we must rely on predictions of accurate stellar evolution models, as well a consideration of what we can observably measure (stellar mass, composition, orbital radius of an exoplanet) in order to create a statistical framework wherein we can identify the best candidate systems for follow-up characterization. In this paper we discuss a statistical approach to constrain long-term planetary habitability by evaluating the likelihood that at a given time of observation, a star would have a planet in the 2 Gy continuously habitable zone (CHZ 2 ). Additionally, we will discuss how we can use existing observational data (i.e. data assembled in the Hypatia catalog and the Kepler exoplanet host star database) for a robust comparison to the catalog of theoretical stellar models.

The Case for Technosignatures: Why They May Be Abundant, Long-lived, Highly Detectable, and Unambiguous

“…For instance, the biosignature search community is developing many mature frameworks for designing and interpreting the results of life detection experiments, including the development and selection of good biosignatures to search for, selection criteria and prioritization of target lists, and frameworks for determining the confidence of detection and dealing with ambiguity (Stark et al 2019;Truitt et al 2020;Tuchow & Wright 2020, 2021Neveu et al 2018;Green et al 2021, to give a few recent examples in addition to the references in Section 1).…”

Potential Habitability as a Stellar Property: Effects of Model Uncertainties and Measurement Precision

“…Values for the fixed age required for sustained habitability range in the literature from 2 Gyr to 4 Gyr (Truitt et al 2020). If one were to select 2 Gyr as the habitable duration required to host biosignatures, then H would have the functional form:…”

Defining the Really Habitable Zone

“…The coefficients encapsulate underlying assumptions of the atmospheric modeling and the weather on the planet, as well as of the properties of the surface of the planet and other unknown planet properties that are beyond the scope of this, and indeed most, papers. We found that there is a lack of general consensus in the literature as to what these parameters should be, and an overall disagreement in the models that should be applied (e.g., Kokaia et al 2020;Truitt et al 2020 Abe et al 2011). In choosing our model parameters for the Really Habitable Zone, we therefore followed what appears to be standard practice, and made-up new coefficients entirely as shown in Table 1 according to our whims.…”