On the Temperature Profiles and Emission Spectra of Mini-Neptune Atmospheres
arXiv:2009.11290 · doi:10.3847/1538-4357/abbfb1
Abstract
Atmospheric observations of mini-Neptunes orbiting M-dwarfs are beginning to provide constraints on their chemical and thermal properties, while also providing clues about their interiors and potential surfaces. With their relatively large scale heights and large planet-star contrasts, mini-Neptunes are currently ideal targets towards the goal of characterising temperate low-mass exoplanets. Understanding the thermal structures and spectral appearances of mini-Neptunes is important to understand various aspects of their atmospheres, including radiative/convective energy transport, boundary conditions for the interior, and their potential habitability. In the present study, we explore these aspects of mini-Neptunes using self-consistent models of their atmospheres. We begin by exploring the effects of irradiation, internal flux, metallicity, clouds and hazes on the atmospheric temperature profiles and thermal emission spectra of temperate mini-Neptunes. In particular, we investigate the impact of these properties on the radiative-convective boundary and the thermodynamic conditions in the lower atmosphere, which serves as the interface with the interior and/or a potential surface. Building on recent suggestions of habitability of the mini-Neptune K2-18 b, we find a range of physically-motivated atmospheric conditions that allow for liquid water under the H_2-rich atmospheres of such planets. We find that observations of thermal emission with JWST/MIRI spectrophotometry can place useful constraints on the habitability of temperate mini-Neptunes such as K2-18 b, and provide more detailed constraints on the chemical and thermal properties of warmer planets such as GJ 3470 b. Our results underpin the potential of temperate mini-Neptunes such as K2-18 b as promising candidates in the search for habitable exoplanets.
arXiv commentAccepted for publication in ApJ, 25 pages, 11 figures
References in corpus (79)
- A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
- The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
- The false positive rate of Kepler and the occurrence of planets
- Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
- Precipitating Condensation Clouds in Substellar Atmospheres
- Mass-Radius Relationships for Solid Exoplanets
- A super-Earth transiting a nearby low-mass star
- Most 1.6 Earth-Radius Planets are not Rocky
- Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
- Atmospheric circulation of hot Jupiters: Coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b
- Disequilibrium Carbon, Oxygen, and Nitrogen Chemistry in the Atmospheres of HD 189733b and HD 209458b
- The Mid-Infrared Instrument for the James Webb Space Telescope I: Introduction
- C/O ratio as a Dimension for Characterizing Exoplanetary Atmospheres
- Neglected Clouds in T and Y Dwarf Atmospheres
- ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K
- Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets
- 3D mixing in hot Jupiter atmospheres. I. application to the day/night cold trap in HD 209458b
- A variationally computed line list for hot NH3
- A New Family of Planets ? "Ocean Planets"
- PandExo: A Community Tool for Transiting Exoplanet Science with JWST & HST
- ExoMol line lists III: An improved hot rotation-vibration line list for HCN and HNC
- Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b
- Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
- Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b
- Chemical consequences of the C/O ratio on hot Jupiters: Examples from WASP-12b,CoRoT-2b, XO-1b, and HD 189733b
- Hydrogen Greenhouse Planets Beyond the Habitable Zone
- Water Vapour Absorption in the Clear Atmosphere of an exo-Neptune
- Water vapour in the atmosphere of the habitable-zone eight Earth-mass planet K2-18 b
- Formation and Structure of Low Density Exo-Neptunes
- Equilibrium chemistry down to 100 K - Impact of silicates and phyllosilicates on carbon/oxygen ratio
- Thermal Emission and Albedo Spectra of Super Earths with Flat Transmission Spectra
- Three Possible Origins for the Gas Layer on GJ 1214b
- A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
- A Sub-Neptune Exoplanet with a Low-Metallicity Methane-Depleted Atmosphere and Mie-Scattering Clouds
- Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1
- Improved HCN/HNC linelist, model atmospheres and synthetic spectra for WZ Cas
- The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST
- Quantitatively Assessing the Role of Clouds in the Transmission Spectrum of GJ 1214b
- HAT-P-26b: A Neptune-Mass Exoplanet with a Well Constrained Heavy Element Abundance
- Bulk Composition of GJ 1214b and other sub-Neptune exoplanets
- Habitable Moist Atmospheres On Terrestrial Planets Near the Inner Edge Of the Habitable Zone Around M-dwarfs
- Thermal evolution and structure models of the transiting super-Earth GJ 1214b
- Water Clouds in Y Dwarfs and Exoplanets
- Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation
- Habitable worlds with JWST: transit spectroscopy of the TRAPPIST-1 system?
- Evolved Climates and Observational Discriminants for the TRAPPIST-1 Planetary System
- Biosignature Gases in H2-Dominated Atmospheres on Rocky Exoplanets
- Scientific Discovery with the James Webb Space Telescope
- Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds
- The Habitability of Proxima Centauri b: II: Environmental States and Observational Discriminants
- A hot Uranus transiting the nearby M dwarf GJ3470. Detected with HARPS velocimetry. Captured in transit with TRAPPIST photometry
- Condensation-inhibited convection in hydrogen-rich atmospheres: Stability against double-diffusive processes and thermal profiles for Jupiter, Saturn, Uranus, and Neptune
- GENESIS: New Self-Consistent Models of Exoplanetary Spectra
- The Mid-Infrared Instrument for the James Webb Space Telescope, III: MIRIM, The MIRI Imager
- The interior and atmosphere of the habitable-zone exoplanet K2-18b
- The Intrinsic Temperature and Radiative-Convective Boundary Depth in the Atmospheres of Hot Jupiters
- A super-Earth and two sub-Neptunes transiting the nearby and quiet M dwarf TOI-270
- Vibrational transition moments of CH from first principles
- The Mid-Infrared Instrument for the James Webb Space Telescope, IX: Predicted Sensitivity
- Theoretical Transit Spectra for GJ 1214b and Other "Super-Earths"
- On Signatures of Clouds in Exoplanetary Transit Spectra
- Constraints on Climate and Habitability for Earth-like Exoplanets Determined from a General Circulation Model
- Exploring atmospheres of hot mini-Neptunes and extrasolar giant planets orbiting different stars with application to HD 97658b, WASP-12b, CoRoT-2b, XO-1b and HD 189733b
- Temperature Structure and Atmospheric Circulation of Dry, Tidally Locked Rocky Exoplanets
- Equatorial anti-rotating day side wind flow in WASP-43b elicited by deep wind jets?
- The Transiting System GJ1214: High-Precision Defocused Transit Observations and a Search for Evidence of Transit Timing Variation
- Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES
- Analyzing Atmospheric Temperature Profiles and Spectra of M dwarf Rocky Planets
- Analytical Models of Exoplanetary Atmospheres. III. Gaseous C-H-O-N Chemistry with 9 Molecules
- Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets
- Transit timing variation and transmission spectroscopy analyses of the hot Neptune GJ3470b
- The GTC exoplanet transit spectroscopy survey. VI. A spectrally-resolved Rayleigh scattering slope in GJ 3470b
- In hot water: effects of temperature-dependent interiors on the radii of water-rich super-Earths
- Models of Neptune-Mass Exoplanets: Emergent Fluxes and Albedos
- Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module
- Hot Hydrogen Climates near the inner edge of the Habitable Zone
- Model atmospheres of sub-stellar mass objects
- Assessing Spectra and Thermal Inversions due to TiO in Hot Jupiter Atmospheres
- Liquid Water Oceans in Ice Giants
Cited by in corpus (23)
- A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve
- Habitability and Biosignatures of Hycean Worlds
- The Hazy and Metal-Rich Atmosphere of GJ 1214 b Constrained by Near and Mid-Infrared Transmission Spectroscopy
- How to identify exoplanet surfaces using atmospheric trace species in hydrogen-dominated atmospheres
- How Deep Is the Ocean? Exploring the phase structure of water-rich sub-Neptunes
- TOI-5205 b: A Short-period Jovian Planet Transiting a Mid-M Dwarf
- Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres
- Where are the Water Worlds?: Self-Consistent Models of Water-Rich Exoplanet Atmospheres
- Characterising Atmospheres of Cloudy Temperate Mini-Neptunes with JWST
- Revisiting Radial Velocity Measurements of the K2-18 System with the Line-by-Line Framework
- Atmospheric dynamics of temperate sub-Neptunes. Part I: dry dynamics
- A sub-Neptune planet around TOI-1695 discovered and characterized with SPIRou and TESS
- Not All Sub-Neptune Exoplanets Have Magma Oceans
- K2, Spitzer, and TESS Transits of Four Sub-Neptune Exoplanets
- Evidence for an Atmosphere on the Ultra-Short Period super-Earth HD 3167 b
- Is the high-energy environment of K2-18b special?
- Three-dimensional Transport-induced Chemistry on Temperate sub-Neptune K2-18b, Part I: the Effects of Atmospheric Dynamics
- Inferring Shallow Surfaces on sub-Neptune Exoplanets with JWST
- A First Look at CRIRES+: Performance Assessment and Exoplanet Spectroscopy
- HyDRo: Atmospheric Retrieval of Rocky Exoplanets in Thermal Emission
- Three-dimensional transport-induced chemistry on temperate sub-Neptune K2-18b, Part II: the combined effects of atmospheric dynamics and chemical reactions
- Impact of Clouds on the Atmosphere-Mantle Interface of Sub-Neptunes
- Photochemistry and Spectral Characterization of Temperate and Gas-Rich Exoplanets