Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST

Greene, Thomas P.; Bell, Taylor; Ducrot, Elsa; Dyrek, Achrène; Lagage, Pierre-Olivier; Fortney, Jonathan J.

doi:10.1038/s41586-023-05951-7

Cited by 104 publications

(80 citation statements)

References 47 publications

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“…These studies complement previous efforts to use secondary eclipse measurements to probe atmospheric composition and thickness on hot rocky exoplanets (Kreidberg et al 2019;Crossfield et al 2022;Whittaker et al 2022). For TRAPPIST-1 b, JWST Program GTO 1177 obtained five secondary eclipse observations with a measured depth of 861 ± 99 ppm in the MIRI F1500W filter (Greene et al 2023). For TRAPPIST-1 c, which receives a similar insolation to Venus in our planetary system, JWST program GO 2304 obtained four secondary eclipse observations with a measured eclipse depth of 421 ± 94 ppm (Zieba et al 2023).…”

Section: Introductionsupporting

confidence: 62%

Potential Atmospheric Compositions of TRAPPIST-1 c Constrained by JWST/MIRI Observations at 15 μm

Lincowski,

Meadows,

Zieba

et al. 2023

ApJL

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The first James Webb Space Telescope observations of TRAPPIST-1 c showed a secondary eclipse depth of 421 ± 94 ppm at 15 μm, which is consistent with a bare rock surface or a thin, O2-dominated, low-CO2 atmosphere. Here we further explore potential atmospheres for TRAPPIST-1 c by comparing the observed secondary eclipse depth to synthetic spectra of a broader range of plausible environments. To self-consistently incorporate the impact of photochemistry and atmospheric composition on atmospheric thermal structure and predicted eclipse depth, we use a two-column climate model coupled to a photochemical model and simulate O2-dominated, Venus-like, and steam atmospheres. We find that a broader suite of plausible atmospheric compositions are also consistent with the data. For lower-pressure atmospheres (0.1 bar), our O2–CO2 atmospheres produce eclipse depths within 1σ of the data, consistent with the modeling results of Zieba et al. However, for higher-pressure atmospheres, our models produce different temperature–pressure profiles and are less pessimistic, with 1–10 bar O2, 100 ppm CO2 models within 2.0σ–2.2σ of the measured secondary eclipse depth and up to 0.5% CO2 within 2.9σ. Venus-like atmospheres are still unlikely. For thin O2 atmospheres of 0.1 bar with a low abundance of CO2 (∼100 ppm), up to 10% water vapor can be present and still provide an eclipse depth within 1σ of the data. We compared the TRAPPIST-1 c data to modeled steam atmospheres of ≤3 bars, which are 1.7σ–1.8σ from the data and not conclusively ruled out. More data will be required to discriminate between possible atmospheres or more definitively support the bare rock hypothesis.

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Section: Introductionsupporting

confidence: 62%

Potential Atmospheric Compositions of TRAPPIST-1 c Constrained by JWST/MIRI Observations at 15 μm

Lincowski,

Meadows,

Zieba

et al. 2023

ApJL

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Section: Introductionmentioning

confidence: 61%

“…Thermal emission observations of Trappist-1b were recently used to infer a dayside brightness temperature of 503 27 26 -+ K (Greene et al 2023). This is consistent with reradiation from an airless dayside as substantial atmospheres (>1 bar) would redistribute heat resulting in a lower dayside brightness temperature (Greene et al 2023). Follow-up work (Ih et al 2023) modeled the dayside thermal emission of Trappist-1b for a wide range of atmospheric compositions and confirmed that >1 bar atmospheres containing even trace amounts of CO 2 are strongly disfavored.…”

Section: Introductionmentioning

confidence: 99%

Implications of Atmospheric Nondetections for Trappist-1 Inner Planets on Atmospheric Retention Prospects for Outer Planets

Krissansen‐Totton

2023

ApJL

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JWST secondary eclipse observations of Trappist-1b seemingly disfavor atmospheres >∼1 bar since heat redistribution is expected to yield dayside emission temperature below the ∼500 K observed. Given the similar densities of Trappist-1 planets, and the theoretical potential for atmospheric erosion around late M dwarfs, this observation might be assumed to imply substantial atmospheres are also unlikely for the outer planets. However, the processes governing atmosphere erosion and replenishment are fundamentally different for inner and outer planets. Here, an atmosphere–interior evolution model is used to show that an airless Trappist-1b (and c) only weakly constrains stellar evolution, and that the odds of outer planets e and f retaining substantial atmospheres remain largely unchanged. This is true even if the initial volatile inventories of planets in the Trappist-1 system are highly correlated. The reason for this result is that b and c sit unambiguously interior to the runaway greenhouse limit, and so have potentially experienced ∼8 Gyr of X-ray and extreme ultraviolet–driven hydrodynamic escape; complete atmospheric erosion in this environment only weakly constrains stellar evolution and escape parameterizations. In contrast, e and f reside within the habitable zone, and likely experienced a comparatively short steam atmosphere during Trappist-1's pre-main sequence, and consequently complete atmospheric erosion remains unlikely across a broad swath of parameter space (e and f retain atmospheres in ∼98% of model runs). Naturally, it is still possible that all Trappist-1 planets formed volatile-poor and are all airless today. But the airlessness of b (and c) does not require this, and as such, JWST transit spectroscopy of e and f remains the best near-term opportunity to characterize the atmospheres of habitable zone terrestrial planets.

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“…M-dwarfs (T eff < 4000 K) are of particular interest in the search for habitable worlds and biosignatures (e.g., Scalo et al 2007;Childs et al 2022;Peterson et al 2023), as they outnumber solar-type stars by an order of magnitude, and the compactness of their habitable zones makes them prime targets for the characterization of exoplanets that transit and are eclipsed by their host star (e.g., TRAPPIST-1, Greene et al 2023). M-dwarfs constituted only a small fraction of the target stars for the Kepler Mission, yet due to the prevalence of small terrestrial planets around these stars, we now have robust estimates on the occurrence of these planets (Dressing & Charbonneau 2015;Hardegree-Ullman et al 2019;Hsu et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Forming Gas Giants around a Range of Protostellar M-dwarfs by Gas Disk Gravitational Instability

Boss,

Kanodia

2023

ApJ

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Recent discoveries of gas giant exoplanets around M-dwarfs from transiting and radial velocity surveys are difficult to explain with core-accretion models. We present here a homogeneous suite of 162 models of gravitationally unstable gaseous disks. These models represent an existence proof for gas giants more massive than 0.1 Jupiter masses to form by the gas disk gravitational instability (GDGI) mechanism around M-dwarfs for comparison with observed exoplanet demographics and protoplanetary disk mass estimates for M-dwarf stars. We use the Enzo 2.6 adaptive mesh refinement (AMR) 3D hydrodynamics code to follow the formation and initial orbital evolution of gas giant protoplanets in gravitationally unstable gaseous disks in orbit around M-dwarfs with stellar masses ranging from 0.1 M ⊙ to 0.5 M ⊙. The gas disk masses are varied over a range from disks that are too low in mass to form gas giants rapidly to those where numerous gas giants are formed, therefore revealing the critical disk mass necessary for gas giants to form by the GDGI mechanism around M-dwarfs. The disk masses vary from 0.01 M ⊙ to 0.05 M ⊙ while the disk to star mass ratios explored the range from 0.04 to 0.3. The models have varied initial outer disk temperatures (10–60 K) and varied levels of AMR grid spatial resolution, producing a sample of expected gas giant protoplanets for each star mass. Broadly speaking, disk masses of at least 0.02 M ⊙ are needed for the GDGI mechanism to form gas giant protoplanets around M-dwarfs.

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Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST

Cited by 104 publications

References 47 publications

Potential Atmospheric Compositions of TRAPPIST-1 c Constrained by JWST/MIRI Observations at 15 μm

Potential Atmospheric Compositions of TRAPPIST-1 c Constrained by JWST/MIRI Observations at 15 μm

Implications of Atmospheric Nondetections for Trappist-1 Inner Planets on Atmospheric Retention Prospects for Outer Planets

Forming Gas Giants around a Range of Protostellar M-dwarfs by Gas Disk Gravitational Instability

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