arXiv subjects

Samantha Gilbert-Janizek

Publications and source records attributed to Samantha Gilbert-Janizek.

5 recordsLinked to original sources

arXiv2026

pyEDITH: the coronagraphic exposure time calculator for the Habitable Worlds Observatory

To support the development of next-generation missions for the search and characterization of habitable planets, high-fidelity tools for astrophysical and instrumental noise simulations are needed. In this paper, we introduce pyEDITH, the Python-based coronagraphic exposure time calculator built for the next recommended NASA flagship mission, the Habitable Worlds Observatory (HWO), tasked with searching for signs of habitability and life in dozens of nearby exoplanet systems. pyEDITH is designed to simulate wavelength-dependent exposure times and signal-to-noise ratios (S/N) for synthetic HWO direct imaging observations, considering realistic engineering specifications and user-defined target information. Its modular architecture ensures flexibility as mission requirements evolve. pyEDITH enables a streamlined integration with modern astronomical workflows and was designed to be used by the scientific community at all skill levels for understanding the capabilities and limitations of different HWO architectures for exoplanet analyses. The code has been validated against existing exposure time calculators and released open-source on GitHub and Zenodo, as well as made accessible through a Graphical User Interface. The pyEDITH package includes API documentation, tutorial notebooks, and has been used in forthcoming scientific publications.

astro-ph.IM↗

arXiv2026

A whole-planet model of the Earth without life for terrestrial exoplanet studies

As the only known habitable (and inhabited) planet in the universe, Earth informs our search for life elsewhere. Future telescopes like the Habitable Worlds Observatory (HWO) will soon look for life on rocky worlds around Sun-like stars, so it is critical that we understand how to distinguish habitable planets from inhabited planets. However, it remains unknown if life is necessary to maintain a habitable planet, or how all of the components of an evolving planet impact habitability over time. As a first step toward answering these questions, we present a coupled interior-atmosphere evolution model of the Earth without life from 50 Myr to 5 Gyr that reproduces 19 key observations of the pre-industrial Earth after 4.5 Gyr within estimated measurement uncertainties. We also produce a reflected light spectrum covering the possible wavelength range of HWO. Our findings suggest that life may not be required to maintain long-term habitable surface conditions. The model presented here is apt for predicting the long-term habitability of Earth-like exoplanets by coupling the interior and surface evolution. By generating realistic reflected light spectra from evolved atmospheric states, this model represents significant progress towards characterizing the observability of whole-planet evolution, which may ultimately provide a robust abiotic baseline for interpreting biosignature observations with HWO.

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arXiv2026

Wavelength Requirements for Life Detection via Reflected Light Spectroscopy of Rocky Exoplanets

Searching for signs of life is a primary goal of the Habitable Worlds Observatory (HWO). However, merely detecting oxygen, methane, or other widely discussed biosignatures is insufficient evidence for a biosphere. In parallel with biosignature detection, exoplanet life detection additionally requires characterization of the broader physicochemical context to evaluate planetary habitability and the plausibility that life could produce a particular biosignature in a given environment. Life detection further requires that we can confidently rule out photochemical or geological phenomena that can mimic life. Evaluating false-positive scenarios may require different observatory specifications than biosignature detection surveys. Here, we explore the coronagraph requirements for assessing habitability and for excluding known false-positive (and false-negative) scenarios for oxygen and methane. We find that broad wavelength coverage ranging from the near ultraviolet (0.26 $μ$m) and extending into the near infrared (1.7 $μ$m) is necessary to contextualize these potential biosignatures with HWO. The short-wavelength cutoff is driven by the need to identify Proterozoic-like biospheres via O$_3$, whereas the long-wavelength cutoff is driven by the need to contextualize O$_2$ and CH$_4$ biosignatures via constraints on carbon-bearing atmospheric species. The ability to obtain spectra with signal-to-noise ratios of 20-40 across this 0.26-1.7 $μ$m range (R=7 UV, R=140 VIS, and R=70 NIR) is also required. While not every Earth-analog biosignature and false positive can be unambiguously identified with these capabilities-and the plausibility and contextual clues of many biosignature false positives remain an area of active research-our minimal spectral recommendations would enable a broad search for Earth-like life assuming such observations are achievable for a meaningful number of HWO targets.

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arXiv2026

The effect of spectral resolution on biosignature detection via reflected light observations of the Earth through time

NASA's Habitable Worlds Observatory (HWO) will search for biosignatures on Earth-like exoplanets using reflected light spectroscopy. A critical instrument design parameter is resolving power, which must balance biosignature detectability against exposure time and detector noise constraints. We assess the resolving power needed to detect and characterize key biosignature gases and habitability indicators including O$_2$, O$_3$, H$_2$O, CH$_4$, CO$_2$ and CO across atmospheres representing the Archean, Proterozoic, and Phanerozoic Earth. We combine analytical detectability calculations spanning spectral resolutions ($λ/Δλ$) $R=20$-$5000$ with atmospheric retrievals using the rfast radiative transfer model and pyEDITH exposure time calculator for realistic wavelength-dependent noise modeling. In the visible ($0.4$-$1.0$ $μ$m), the nominal resolution $R_{Vis}=140$ is sufficient for detecting O$_2$ in Phanerozoic-like atmospheres. Higher resolutions could theoretically reduce exposure times for low-O$_2$ Proterozoic atmospheres, but require $>10\times$ reductions in dark current and could increase H$_2$O detection exposure times by $\sim 2\times$, penalizing the foundational habitability constraint that anchors downstream biosignature searches. The most efficient path for low-O$_2$ atmospheres may instead be indirect inference via O$_3$, whose Hartley-Huggins bands are detectable at $R_{UV}\sim 7$. In the near-IR ($1.0$-$1.7$ $μ$m), $R_{NIR}\geq40$ is necessary to avoid a degeneracy between CO$_2$ and CO that could produce false positive detections of abundant CO. The nominal $R_{NIR}=70$ is sufficient for characterizing all Earth-through-time cases. These results support HWO's current baseline resolution choices and provide actionable guidance for finalizing spectrometer requirements while maintaining technological feasibility for the search for life on exoplanets.

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arXiv2024

Retrieved Atmospheres and Inferred Surface Properties for Exoplanets Using Transmission and Reflected Light Spectroscopy

Future astrophysics missions will seek extraterrestrial life via transmission and direct imaging observations. To assess habitability and biosignatures, we need robust retrieval tools to analyze observed spectra, and infer surface and atmospheric properties with their uncertainties. We use a novel retrieval tool to assess accuracy in characterizing near-surface habitability and biosignatures via simulated transmission and direct imaging spectra, based on the Origins Space Telescope (Origins) and LUVOIR mission concepts. We assess our ability to discriminate between an Earth-like and a false-positive O$_3$ TRAPPIST-1 e with transmission spectroscopy. In reflected light, we assess the robustness of retrieval results to un-modeled cloud extinction. We find that assessing habitability using transmission spectra may be challenging due to relative insensitivity to surface temperature and near-surface H$_2$O abundances. Nonetheless, our order of magnitude H$_2$O constraints can discriminate extremely desiccated worlds. Direct imaging is insensitive to surface temperature and subject to the radius/albedo degeneracy, but this method proves highly sensitive to surface water abundance, achieving retrieval precision within 0.1% even with partial clouds. Concerning biosignatures, Origins-like transmission observations ($t=40$ hours) may detect the CO$_2$/CH$_4$ pair on M-dwarf planets and differentiate between biological and false positive O$_3$ using H$_2$O and abundant CO. In contrast, direct imaging observations with LUVOIR-A ($t=10$ hours) are better suited to constraining O$_2$ and O$_3$, and may be sensitive to wavelength-dependent water cloud features, but will struggle to detect modern Earth-like abundances of methane. For direct imaging, we weakly detect a stratospheric ozone bulge by fitting the near-UV wings of the Hartley band.

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