Illusion and Reality in the Atmospheres of Exoplanets
arXiv:1701.00493
Abstract
The atmospheres of exoplanets reveal all their properties beyond mass, radius, and orbit. Based on bulk densities, we know that exoplanets larger than 1.5 Earth radii must have gaseous envelopes, hence atmospheres. We discuss contemporary techniques for characterization of exoplanetary atmospheres. The measurements are difficult, because - even in current favorable cases - the signals can be as small as 0.001-percent of the host star's flux. Consequently, some early results have been illusory, and not confirmed by subsequent investigations. Prominent illusions to date include polarized scattered light, temperature inversions, and the existence of carbon planets. The field moves from the first tentative and often incorrect conclusions, converging to the reality of exoplanetary atmospheres. That reality is revealed using transits for close-in exoplanets, and direct imaging for young or massive exoplanets in distant orbits. Several atomic and molecular constituents have now been robustly detected in exoplanets as small as Neptune. In our current observations, the effects of clouds and haze appear ubiquitous. Topics at the current frontier include the measurement of heavy element abundances in giant planets, detection of carbon-based molecules, measurement of atmospheric temperature profiles, definition of heat circulation efficiencies for tidally locked planets, and the push to detect and characterize the atmospheres of super-Earths. Future observatories for this quest include the James Webb Space Telescope, and the new generation of Extremely Large Telescopes on the ground. On a more distant horizon, NASA's concepts for the HabEx and LUVOIR missions could extend the study of exoplanetary atmospheres to true twins of Earth.
arXiv commentInvited Review for the 25th Anniversary issue of JGR Planets, in press
References in corpus (81)
- Direct Imaging of Multiple Planets Orbiting the Star HR 8799
- Detection of an Extrasolar Planet Atmosphere
- A terrestrial planet candidate in a temperate orbit around Proxima Centauri
- A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
- The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b
- Mass-Radius Relationships for Solid Exoplanets
- Theoretical Transmission Spectra During Extrasolar Giant Planet Transits
- Infrared radiation from an extrasolar planet
- Infrared Transmission Spectroscopy of the Exoplanets HD209458b and XO-1b Using the Wide Field Camera-3 on the Hubble Space Telescope
- The 3.6-8.0 Micron Broadband Emission Spectrum of HD 209458b: Evidence for an Atmospheric Temperature Inversion
- Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
- Exoplanet Atmospheres
- The signature of orbital motion from the dayside of the planet tau Bootis b
- A Precise Water Abundance Measurement for the Hot Jupiter WASP-43b
- Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
- A ground-based transmission spectrum of the super-Earth exoplanet GJ1214b
- The Statistics of Albedo and Heat Recirculation on Hot Exoplanets
- Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
- High C/O Ratio and Weak Thermal Inversion in the Very Hot Atmosphere of Exoplanet WASP-12b
- 3.6 and 4.5 Micron Phase Curves and Evidence for Non-Equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b
- Photometric Light Curves and Polarization of Close-in Extrasolar Giant Planets
- Transitions in the cloud composition of hot Jupiters
- A Framework for Characterizing the Atmospheres of Low-Mass Low-Density Transiting Planets
- A map of the large day-night temperature gradient of a super-Earth exoplanet
- Inference of Inhomogeneous Clouds in an Exoplanet Atmosphere
- Finding extraterrestrial life using ground-based high-resolution spectroscopy
- Discovery and Characterization of Transiting SuperEarths Using an All-Sky Transit Survey and Follow-up by the James Webb Space Telescope
- Atmospheric Circulation of Hot Jupiters: Three-dimensional circulation models of HD 209458b and HD 189733b with Simplified Forcing
- Alien Maps of an Ocean-Bearing World
- Detection of H2O and evidence for TiO/VO in an ultra hot exoplanet atmosphere
- Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres
- A Systematic Retrieval Analysis of Secondary Eclipse Spectra II: A Uniform Analysis of Eight Planets and Their C to O Ratios
- Ranges of Atmospheric Mass and Composition of Super Earth Exoplanets
- A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c
- A global cloud map of the nearest known brown dwarf
- HST hot Jupiter Transmission Spectral Survey: A detection of Na and strong optical absorption in HAT-P-1b
- Inverting Phase Functions to Map Exoplanets
- Thermal Phase Variations of WASP-12b: Defying Predictions
- Very Low-Density Planets around Kepler-51 Revealed with Transit Timing Variations and an Anomaly Similar to a Planet-Planet Eclipse Event
- Temperature-Pressure Profile of the hot Jupiter HD 189733b from HST Sodium Observations: Detection of Upper Atmospheric Heating
- An Upper Limit on the Reflected Light from the Planet Orbiting the Star tau Bootis
- Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b
- The atmospheric circulation of a nine-hot Jupiter sample: Probing circulation and chemistry over a wide phase space
- Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets
- A Two-Dimensional Infrared Map of the Extrasolar Planet HD 189733b
- Atmospheric Dynamics of Hot Exoplanets
- A new look at NICMOS transmission spectroscopy of HD189733, GJ-436 and XO-1: no conclusive evidence for molecular features
- Characterizing Transiting Planet Atmospheres through 2025
- Biosignature Gases in H2-Dominated Atmospheres on Rocky Exoplanets
- New Analysis Indicates No Thermal Inversion in the Atmosphere of HD 209458b
- Observations of Exoplanet Atmospheres
- Balancing the Energy Budget of Short-Period Giant Planets: Evidence for Reflective Clouds and Optical Absorbers
- Probing the terminator region atmosphere of the Hot-Jupiter XO-1b with transmission spectroscopy
- Outgassing of Ordinary Chondritic Material and Some of its Implications for the Chemistry of Asteroids, Planets, and Satellites
- 3.6 and 4.5 m Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b
- Hubble Space Telescope hot Jupiter Transmission Spectral Survey: detection of water in HAT-P-1b from Wide Field Camera 3 near-infrared spatial scan observations
- Near-IR Direct Detection of Water Vapor in Tau Boo b
- Probable detection of starlight reflected from the giant exoplanet orbiting tau Bootis
- GTC OSIRIS transiting exoplanet atmospheric survey: detection of sodium in XO-2b from differential long-slit spectroscopy
- 3.6 and 4.5 m Phase Curves of the Highly-Irradiated Eccentric Hot Jupiter WASP-14b
- Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
- Spitzer Secondary Eclipses of WASP-18b
- Highlights in the Study of Exoplanet Atmospheres
- Gemini Planet Imager Spectroscopy of the HR 8799 planets c and d
- Features in the Broadband Eclipse Spectra of Exoplanets: Signal or Noise?
- A Cloudiness Index for Transiting Exoplanets Based on the Sodium and Potassium Lines: Tentative Evidence for Hotter Atmospheres Being Less Cloudy at Visible Wavelengths
- Spitzer/MIPS 24 micron Observations of HD 209458b: 3 eclipses, 2.5 transits, and a Phase Curve Corrupted by Instrumental Sensitivity Variations
- A Survey of Alkali Line Absorption in Exoplanetary Atmospheres
- The upper atmosphere of the exoplanet HD209458b revealed by the sodium D lines: Temperature-pressure profile, ionization layer, and thermosphere
- Detection of visible light from the darkest world
- The First H-band Spectrum of the Massive Gas Giant Planet beta Pictoris b with the Gemini Planet Imager
- A Sensitive Search for Methane in the Infrared Spectrum of Tau Bootis
- On the Stability of Super-Earth Atmospheres
- Atmospheric Lensing and Oblateness Effects During an Extrasolar Planetary Transit
- Blind extraction of an exoplanetary spectrum through Independent Component Analysis
- Atmospheric Circulation of Eccentric Hot Jupiter HAT-P-2b
- Non-Detection of Polarized, Scattered Light from the HD 189733b Hot Jupiter
- Extrasolar Carbon Planets
- GTC OSIRIS transiting exoplanet atmospheric survey: detection of potassium in HAT-P-1b from narrowband spectrophotometry
- The polarisation of HD 189733
- Characterizing the Atmospheres of the HR8799 Planets with HST/WFC3