Exoplanetology: Exoplanets & Exomoons

Setting The Stage For The Search For Life With The Habitable Worlds Observatory: Properties Of 164 Promising Planet-survey Targets

By Keith Cowing
Status Report
The Astrophysical Journal
July 18, 2024
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Setting The Stage For The Search For Life With The Habitable Worlds Observatory: Properties Of 164 Promising Planet-survey Targets
Setting The Stage For The Search For Life With The Habitable Worlds Observatory: Properties Of 164 Promising Planet-survey Targets

The Decadal Survey on Astronomy and Astrophysics 2020 has recommended that NASA realize a large IR/optical/UV space telescope optimized for high-contrast imaging and spectroscopy of ∼25 exo-Earths and transformative general astrophysics.

The NASA Exoplanet Exploration Program (ExEP) has subsequently released a list of 164 nearby (d < 25 pc) targets deemed the most accessible to survey for potentially habitable exoplanets with the Habitable Worlds Observatory (HWO).

We present a catalog of system properties for the 164 ExEP targets, including 1744 abundance measurements for 14 elements from the Hypatia Catalog and 924 photometry measurements spanning from 151.6 nm to 22 μm in the GALEX, Strömgren, Tycho, Gaia, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer bandpasses.

We independently derive stellar properties for these systems by modeling their spectral energy distributions with Bayesian model averaging. Additionally, by consulting the literature, we identify TESS flare rates for 46 stars, optical variability for 78 stars, and X-ray emission for 46 stars in our sample.

We discuss our catalog in the context of planet habitability and draw attention to key gaps in our knowledge where precursor science can help to inform HWO mission design trade studies in the near future. Notably, only 33 of the 164 stars in our sample have reliable space-based UV measurements, and only 40 have a mid-IR measurement.

We also find that phosphorus, a bioessential element, has only been measured in 11 of these stars, motivating future abundance surveys. Our catalog is publicly available and we advocate for its use in future studies of promising HWO targets.

Our updated catalog of properties of 164 promising targets for HWO includes 924 photometry measurements in 18 different bandpasses spanning from 151.6 nm to 22 μm, 1744 abundance measurements for 14 different elements, variability metrics for 78 stars, X-ray detections for 46 stars, and flare rates for 46 stars. A more granular summary of the catalog properties is presented in Figure 11, and key physical and observable properties of the stars in our catalog are plotted in Figure 12. This catalog of stellar properties is intended to provide a starting point for future precursor and preparatory science leading up to HWO’s final mission design and eventual launch in the 2040s.

Bar graph showing a summary of the information in our catalog, demonstrating the (in)completeness of our knowledge about these systems. Each attribute is subdivided into the three tier levels defined by Mamajek & Stapelfeldt (2023).– The Astrophysical Journal

Setting the Stage for the Search for Life with the Habitable Worlds Observatory: Properties of 164 Promising Planet-survey Targets, The Astrophysical Journal (open access)

Astrobiology

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) 🖖🏻