Limits on Clouds and Hazes for the TRAPPIST-1 Planets

Moran, Sarah E.; Hörst, Sarah M.; Batalha, Natasha E.; Lewis, Nikole K.; Wakeford, Hannah R.

doi:10.3847/1538-3881/aae83a

Cited by 60 publications

(68 citation statements)

References 80 publications

(147 reference statements)

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“…No prominent absorption features at near-infrared wavelengths in the transmission spectra of the atmospheres of the TRAPPIST-1 planets rule out cloud-free, hydrogen-rich atmospheres (de Wit et al 2016(de Wit et al , 2018Zhang et al 2018;Burdanov et al 2019), whereas a clear hydrogen-rich atmosphere for TRAPPIST-1 f and 1 g is still in dispute (de Wit et al 2018;Moran et al 2018;Wakeford et al 2019). Our results show that all the TRAPPIST-1 planets used to have a hydrogen-rich atmosphere of 10 −2 − 1 wt% just after disk dispersal.…”

Section: Discussionmentioning

confidence: 59%

“…The combined spectrum of the planets rules out cloud-free, hydrogen-dominated atmospheres, except for TRAPPIST-1 f and 1 g (de Wit et al 2018;Moran et al 2018); Wakeford et al (2019) recently suggested that a clear hydrogen-dominated atmosphere may be ruled out for TRAPPIST-1 g. Since high-altitude clouds and haze are not expected to form in hydrogen-dominated atmospheres around temperate planets (e.g. Morley et al 2015), transit spectroscopy of the TRAPPIST-1 planets suggests no atmosphere or a high-metallicity atmosphere referred to as a secondary atmosphere.…”

Section: Introductionmentioning

confidence: 98%

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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: 59%

Section: Introductionmentioning

confidence: 98%

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

Hori

Ogihara

2020

ApJ

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“…We simulate the transmission spectra for R = 300 from 0.6−5.3 µm relevant for the NIRSpec/PRISM instrument on JWST, which has been shown to be the ideal instrument for JWST characterization of terrestrial exoplanets (Batalha et al 2018. We use the PSG imager noise model and do not include a noise floor in our simulated spectra.…”

Section: Simulated Observablesmentioning

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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“…Transits from seven small rocky planets on short period orbits were found, allowing detailed studies to be conducted on the possible atmospheres and their constituents of small planets orbiting a single star, and hence with similar initial conditions (e.g. Alberti et al 2017;Ducrot et al 2018;Moran et al 2018;Miles-Páez et al 2019;Burdanov et al 2019).…”

Section: Introductionmentioning

confidence: 99%

GJ 357: a low-mass planetary system uncovered by precision radial velocities and dynamical simulations

Jenkins

Pozuelos

Tuomi

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We report the detection of a new planetary system orbiting the nearby M2.5V star GJ 357, using precision radial-velocities from three separate echelle spectrographs, HARPS, HiRES, and UVES. Three small planets have been confirmed in the system, with periods of 9.125±0.001, 3.9306±0.0003, and 55.70±0.05 days, and minimum masses of 3.33±0.48, 2.09±0.32, and 6.72±0.94 M ⊕ , respectively. The second planet in our system, GJ 357c, was recently shown to transit by the Transiting Exoplanet Survey Satellite (TESS; Luque et al. 2019), but we could find no transit signatures for the other two planets. Dynamical analysis reveals the system is likely to be close to coplanar, is stable on Myrs timescales, and places strong upper limits on the masses of the two non-transiting planets b and d of 4.25 and 11.20 M ⊕ , respectively. Therefore, we confirm the system contains at least two super-Earths, and either a third super-Earth or mini-Neptune planet. GJ 357b & c are found to be close to a 7:3 mean motion resonance, however no libration of the orbital parameters was found in our simulations. Analysis of the photometric lightcurve of the star from the TESS, when combined with our radial-velocities, reveal GJ 357c has an absolute mass, radius, and density of 2.248 +0.117 −0.120 M ⊕ , 1.167 +0.037 −0.036 R ⊕ , and 7.757 +0.889 −0.789 gcm −3 , respectively. Comparison to super-Earth structure models reveals the planet is likely an iron dominated world. The GJ 357 system adds to the small sample of low-mass planetary systems with well constrained masses, and further observational and dynamical follow-up is warranted to better understand the overall population of small multi-planet systems in the solar neighbourhood.

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Limits on Clouds and Hazes for the TRAPPIST-1 Planets

Cited by 60 publications

References 80 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

GJ 357: a low-mass planetary system uncovered by precision radial velocities and dynamical simulations

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