High-Resolution Spectral Models Of TRAPPIST-1e Seen As A Pale Blue Dot For ELT And JWST Observations

By Keith Cowing
Press Release
September 7, 2022
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High-Resolution Spectral Models Of TRAPPIST-1e Seen As A Pale Blue Dot For ELT And JWST Observations
Reflection spectra for 1 bar modern Earth TRAPPIST-1e models with four surface compositions shown at R = 300. The spectra are shown in two units: (top row) absolute flux and (bottom row) planet-to-star flux contrast ratio (𝐹p/𝐹∗). Modern Earth-like surface with 44 per cent cloud coverage is shown in black, cloud-free modern Earth-like surface in red, ocean planet with 44 per cent cloud coverage in blue, 100 per cent cloudy planet in yellow, and a planet with flat 0.31 albedo in sky blue. The spectra are shown in two wavelength ranges: 0.4–2.7 𝜇m (left) and 2.7–5.0 𝜇m (right). The two wavelength ranges are shown in different scales for clarity and major spectral features are labeled. Ranges of common photometric bands are shown below the spectra. Presence of clouds significantly increases the overall spectral flux. The flat 0.31 albedo is an acceptable approximation in visible, but overestimates the reflected flux in NIR

Rocky exoplanets orbiting in the habitable zone (HZ) of nearby M dwarfs provide unique opportunities for characterizing their atmospheres and searching for biosignature gases. TRAPPIST-1e, a temperate Earth-sized exoplanet in the HZ of a nearby M dwarf, is arguably the most favorable target for ground- and space-based atmospheric characterization by the extremely large telescopes (ELTs) and the James Webb Space Telescope (JWST).

To inform future observations in reflected and emitted lights using these upcoming telescopes, we simulate the high-resolution reflection and emission spectra for TRAPPIST-1e for both modern and prebiotic Earth-like atmospheric compositions. To demonstrate the effects of wavelength-dependent albedo on climate and spectra, we further simulate five albedo scenarios for each atmospheric composition: cloudy modern Earth-like, cloud-free modern Earth-like, cloudy ocean planet, 100 per cent cloudy planet, and wavelength-independent albedo of 0.31.

We use the recent Mega-MUSCLES spectral energy distribution (SED) of TRAPPIST-1 for our models. We show that the O2 + CH4 and O3 + CH4 biosignature pairs as well as climate indicators (CO2 and H2O) show features in both high-resolution reflection and emission spectra of TRAPPIST-1e that the ELTs can search for. Our high-resolution database for modern and prebiotic Earth TRAPPIST-1e models with various surface compositions and cloud distributions provides a tool for observers to train retrieval algorithms and plan observation strategies to characterize this potentially habitable world.

Zifan Lin, Lisa Kaltenegger

Comments: 8 pages, 5 figures, 1 table. Accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2209.02875 [astro-ph.EP] (or arXiv:2209.02875v1 [astro-ph.EP] for this version)
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Submission history
From: Zifan Lin
[v1] Wed, 7 Sep 2022 01:35:14 UTC (3,006 KB)
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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) 🖖🏻