The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST

Lustig‐Yaeger, Jacob; Meadows, Victoria; Lincowski, Andrew

doi:10.3847/1538-3881/ab21e0

Cited by 225 publications

(306 citation statements)

References 100 publications

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“…Thus, a Venus-like atmosphere as well water vapor might be a plausible solution to the atmospheric compositions of the TRAPPIST-1 planets, which is favored by their flat and featureless transmission spectra. If the TRAPPIST-1 planets possess terrestrial-like atmospheres containing CO 2 , CO 2 absorption will be detectable in transmission spectra acquired in less than 10 transits with James Webb Space Telescope/NIRSpec Prism, although the detection of O 2 and O 3 will be still be elusive (Lustig-Yaeger et al 2019).…”

Section: Discussionmentioning

confidence: 99%

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Hori

Ogihara

2020

ApJ

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Recently, transmission spectroscopy in the atmospheres of the TRAPPIST-1 planets revealed flat and featureless absorption spectra, which rule out cloud-free, hydrogen-dominated atmospheres. Earthsized planets orbiting TRAPPIST-1 likely have either a clear or a cloudy/hazy, hydrogen-poor atmosphere. In this paper, we investigate whether a proposed formation scenario is consistent with expected atmospheric compositions of the TRAPPIST-1 planets. We examine the amount of a hydrogen-rich gas that TRAPPIST-1-like planets accreted from the ambient disk until disk dispersal. Since TRAPPIST-1 planets are trapped into a resonant chain, we simulate disk gas accretion onto a migrating TRAPPIST-1-like planet. We find that the amount of an accreted hydrogen-rich gas is as small as 10 −2 wt% and 0.1 wt% for TRAPPIST-1 b and 1 c, 10 −2 wt% for 1 d, 1 wt% for 1 e, a few wt% for 1 f and 1 g and 1 wt% for 1 h, respectively. We also calculate the long-term thermal evolution of TRAPPIST-1-like planets after disk dissipation and estimate the mass loss of their hydrogen-rich atmospheres driven by a stellar X-ray and UV irradiation. We find that all the accreted hydrogen-rich atmospheres can be lost via hydrodynamic escape. Therefore, we conclude that TRAPPIST-1 planets should have no primordial hydrogen-rich gases but secondary atmospheres such as a Venus-like one and water vapor, if they currently retain atmospheres.

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Section: Discussionmentioning

confidence: 99%

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Hori

Ogihara

2020

ApJ

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“…Because TRAPPIST-1 is not continuously visible, Lustig-Yaeger et al (2019) find that JWST will have 123 opportunities in its nominal 5 year lifetime to observe the transit of TRAPPIST-1d, which has an orbital period of 4.05 days. Assuming the same visibility as TRAPPIST-1, the number of observable transits would decrease to 31 for a planet with an orbital period of 16 days.…”

Section: Detectability Of Molecular Featuresmentioning

confidence: 99%

“…Recent climate modeling has begun to explore how clouds affect the detection of transmission spectral features with JWST. Using the one-dimensional climate and photochemical models of Lincowski et al (2018), Lustig-Yaeger et al (2019) found that clouds inhibit the detection of water features on TRAPPIST-1e. However, three-dimensional simulations are necessary to accurately simulate cloud and water vapor mixing ratios.…”

Section: Introductionmentioning

confidence: 99%

Clouds will Likely Prevent the Detection of Water Vapor in JWST Transmission Spectra of Terrestrial Exoplanets

Komacek

Fauchez

Wolf

et al. 2020

ApJL

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We are on the verge of characterizing the atmospheres of terrestrial exoplanets in the habitable zones of M dwarf stars. Due to their large planet-to-star radius ratios and higher frequency of transits, terrestrial exoplanets orbiting M dwarf stars are favorable for transmission spectroscopy. In this work, we quantify the effect that water clouds have on the amplitude of water vapor transmission spectral features of terrestrial exoplanets orbiting M dwarf stars. To do so, we make synthetic transmission spectra from general circulation model (GCM) experiments of tidally locked planets. We improve upon previous work by considering how varying a broad range of planetary parameters affects transmission spectra. We find that clouds lead to a 10-100 times increase in the number of transits required to detect water features with the James Webb Space Telescope (JWST) with varying rotation period, incident stellar flux, surface pressure, planetary radius, and surface gravity. We also find that there is a strong increase in the dayside cloud coverage in our GCM simulations with rotation periods 12 days for planets with Earth's radius. This increase in cloud coverage leads to even stronger muting of spectral features for slowly rotating exoplanets orbiting M dwarf stars. We predict that it will be extremely challenging to detect water transmission features in the atmospheres of terrestrial exoplanets in the habitable zone of M dwarf stars with JWST. However, species that are well-mixed above the cloud deck (e.g., CO 2 and CH 4 ) may still be detectable on these planets with JWST.

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“…Moreover, results suggest that a few bars of surface CO 2 are needed to maintain ice-free surfaces on TRAPPIST-1f and g. Grimm et al (2018) has found that while TRAPPIST-1e may have a large rocky interior, TRAPPIST-1f and -1g are likely to be volatile rich. Note that 1-D climate model simulations have also been used for TRAPPIST-1 planets (Morley et al 2017;Lincowski et al 2018;Lustig-Yaeger et al 2019) with the limitations of this approach described earlier. For instance, in their simulated transmission spectra Morley et al (2017), considers clear sky atmospheres, while it is not realistic when H 2 O or CO 2 are in the atmosphere and could eventually form clouds, or CH 4 and H 2 SO 4 which could form organic and sulfuric hazes.…”

Section: Introductionmentioning

confidence: 99%

Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System

Fauchez

Turbet

Villanueva

et al. 2019

ApJ

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137

202

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The TRAPPIST-1 system, consisting of an ultra-cool host star having seven known Earth-size planets will be a prime target for atmospheric characterization with JWST. However, the detectability of atmospheric molecular species may be severely impacted by the presence of clouds and/or hazes. In this work, we perform 3-D General Circulation Model (GCM) simulations with the LMD Generic model supplemented by 1-D photochemistry simulations at the terminator with the Atmos model to simulate several possible atmospheres for TRAPPIST-1e, 1f and 1g: 1) modern 2 Fauchez et al.Earth, 2) Archean Earth, and 3) CO 2 -rich atmospheres. JWST synthetic transit spectra were computed using the GSFC Planetary Spectrum Generator (PSG). We find that TRAPPIST-1e, 1f and 1g atmospheres, with clouds and/or hazes, could be detected using JWST's NIRSpec prism from the CO 2 absorption line at 4.3 µm in less than 15 transits at 3 σ or less than 35 transits at 5 σ. However, our analysis suggests that other gases would require hundreds (or thousands) of transits to be detectable. We also find that H 2 O, mostly confined in the lower atmosphere, is very challenging to detect for these planets or similar systems if the planets' atmospheres are not in a moist greenhouse state. This result demonstrates that the use of GCMs, self-consistently taking into account the effect of clouds and sub-saturation, is crucial to evaluate the detectability of atmospheric molecules of interest as well as for interpreting future detections in a more global (and thus robust and relevant) approach.

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The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST

Cited by 225 publications

References 100 publications

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Clouds will Likely Prevent the Detection of Water Vapor in JWST Transmission Spectra of Terrestrial Exoplanets

Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System

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