Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST

Abstract

Nine transiting Earth-sized planets have recently been discovered around nearby late M dwarfs, including the TRAPPIST-1 planets and two planets discovered by the MEarth survey, GJ 1132b and LHS 1140b. These planets are the smallest known planets that may have atmospheres amenable to detection with JWST. We present model thermal emission and transmission spectra for each planet, varying composition and surface pressure of the atmosphere. We base elemental compositions on those of Earth, Titan, and Venus and calculate the molecular compositions assuming chemical equilibrium, which can strongly depend on temperature. Both thermal emission and transmission spectra are sensitive to the atmospheric composition; thermal emission spectra are sensitive to surface pressure and temperature. We predict the observability of each planet's atmosphere with JWST. GJ 1132b and TRAPPIST-1b are excellent targets for emission spectroscopy with JWST/MIRI, requiring fewer than 10 eclipse observations. Emission photometry for TRAPPIST-1c requires 5-15 eclipses; LHS 1140b and TRAPPIST-1d, TRAPPIST-1e, and TRAPPIST-1f, which could possibly have surface liquid water, may be accessible with photometry. Seven of the nine planets are strong candidates for transmission spectroscopy measurements with JWST, though the number of transits required depends strongly on the planets' actual masses. Using the measured masses, fewer than 20 transits are required for a 5 sigma detection of spectral features for GJ 1132b and six of the TRAPPIST-1 planets. Dedicated campaigns to measure the atmospheres of these nine planets will allow us, for the first time, to probe formation and evolution processes of terrestrial planetary atmospheres beyond our solar system.

20 pages, 19 figures. Published in ApJ

References in corpus (13)

• The K2 Mission: Characterization and Early results
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• Synthetic Spectra and Colors of Young Giant Planet Atmospheres: Effects of Initial Conditions and Atmospheric Metallicity
• Chemical enrichment of giant planets and discs due to pebble drift
• Abiotic oxygen-dominated atmospheres on terrestrial habitable zone planets
• Predictions of the atmospheric composition of GJ 1132b
• Could we identify hot Ocean-Planets with CoRoT, Kepler and Doppler velocimetry?
• Prospects for Characterizing the Atmosphere of Proxima Centauri b
• Habitability of waterworlds: runaway greenhouses, atmospheric expansion and multiple climate states of pure water atmospheres
• The Pale Green Dot: A Method to Characterize Proxima Centauri b using Exo-Aurorae
• Comparative Climates of TRAPPIST-1 planetary system: results from a simple climate-vegetation model

Cited by in corpus (11)

• The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST
• The L 98-59 System: Three Transiting, Terrestrial-Sized Planets Orbiting a Nearby M-dwarf
• Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
• Early 2017 observations of TRAPPIST-1 with $\text{Spitzer}$
• The atmospheric circulation and climate of terrestrial planets orbiting Sun-like and M-dwarf stars over a broad range of planetary parameters
• Planet-Planet Occultations in TRAPPIST-1 and Other Exoplanet Systems
• Observing Isotopologue Bands in Terrestrial Exoplanet Atmospheres with the James Webb Space Telescope---Implications for Identifying Past Atmospheric and Ocean Loss
• Lyman-alpha in the GJ 1132 System: Stellar Emission and Planetary Atmospheric Evolution
• Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared
• Simulating Radial Velocity Observations of Trappist-1 with SPIRou
• The Oxyometer: A Novel Instrument Concept for Characterizing Exoplanet Atmospheres