Habitable Zones

Bioverse: Assessing the Ability of Direct Imaging Surveys to Empirically Constrain the Habitable Zone via Trends in Albedo

By Keith Cowing

Status Report

astro-ph.EP

September 10, 2025

Filed under astro-ph.EP, astronomy, Bioverse, coronagraphy, exoplanet, Habitable Worlds Observatory, Habitable Zone, imaging

Bioverse: Assessing the Ability of Direct Imaging Surveys to Empirically Constrain the Habitable Zone via Trends in Albedo — Example Bioverse simulation of a survey to characterize Earth-sized planets in the HZ. This simulation used an 8m diameter telescope observing at λ= 550nm. This figure shows all rocky planets detected with R_p < 1.4R_⊕. Left panel shows the measured quantity of β = A_gR^2Φ(α) as a function of instellation. Individual components of albedo, radius, and phase angle drawn from the Bioverse planet generation process including our injected trend are shown in the right subplots. This survey yields 44 exoEarth candidates, and the distribution of β shows a decrease at instellations corresponding to the HZ, reflecting the injected trend in albedo (see upper right panel). — astro-ph.EP

Will future direct imaging missions such as NASA’s upcoming Habitable Worlds Observatory (HWO) be able to understand Earth-sized planets as a population?

In this study, we simulate the ability of space-based coronagraphy missions to uncover trends in planetary albedo as a function of instellation, and potentially constrain the boundaries of the habitable zone.

We adapt the Bioverse statistical comparative planetology framework to simulate the scientific output of possible designs for HWO. With this tool, we generate a synthetic planetary population with injected population-level trends in albedo and simulate the observability of planets. We then determine the statistical power to which these trends can be recovered as a function of the strength of the injected trend and the sample size of Earth-sized planets in the habitable zone (exoEarths).

The strongest trends in albedo require a sample size of roughly 25-30 exoEarths to recover with high confidence. However, for weaker albedo trends, the required number of planets increases rapidly. If a mission is designed to meet the Decadal Survey’s requirement of 25 exoEarths, it would be able to recover very strong trends in albedo associated with the habitable zone, but would struggle to confidently detect weaker trends.

We explore multiple strategies to increase one’s ability to recover weak trends, such as reducing the uncertainties in observables, incorporating additional observables such as planet colors, and obtaining direct constraints on planetary albedo from full spectral retrievals.

Noah W. Tuchow, Christopher C. Stark, Daniel Apai, Martin Schlecker, Kevin K. Hardegree-Ullman

Comments: Accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2509.07297 [astro-ph.EP] (or arXiv:2509.07297v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2509.07297
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Submission history
From: Noah Tuchow
[v1] Tue, 9 Sep 2025 00:03:58 UTC (2,074 KB)
https://arxiv.org/abs/2509.07297
Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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