Characterizing Transiting Planet Atmospheres through 2025

Cowan, Nicolas B.; Greene, T. P.; Angerhausen, Daniel; Batalha, Natasha E.; Clampin, Mark; Colón, Knicole D.; Crossfield, Ian J. M.; Fortney, J. J.; Gaudi, B. Scott; Harrington, J.; Iro, Nicolas; Lillie, Chuck; Linsky, Jeffrey L.; López‐Morales, Mercedes; Mandell, Avi M.; Stevenson, Kevin B.

doi:10.1086/680855

Cited by 139 publications

(121 citation statements)

References 140 publications

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“…The planet's transmission and emission spectra are sensitive to the relative abundances of O 2 , H 2 O, and other species (Benneke & Seager 2012), and these spectra will be measurable with deep observations from the ground (Snellen et al 2013;Rodler & López-Morales 2014) or from space (Cowan et al 2015;Barstow et al 2016, and references therein). Complementary JWST observations of GJ 1132b's thermal phase curve could reveal its total atmospheric mass, and therefore determine whether the present-day atmosphere is thick or tenuous (Selsis et al 2011;Koll & Abbot 2015).…”

Section: Predictions For Gj 1132bmentioning

confidence: 99%

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

Schaefer

Wordsworth²,

Berta-Thompson

et al. 2016

ApJ

167

279

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GJ 1132b is a nearby Earth-sized exoplanet transiting an M dwarf, and is among the most highly characterizable small exoplanets currently known. In this paper,we study the interaction of a magma ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the amount of O 2 that can build up in the atmosphere as a result of hydrogen dissociation and loss. We find that the magma ocean absorbs at most ∼10% of the O 2 produced, whereas more than 90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132b from our simulations is a tenuous atmosphere dominated by O 2 , though, for very large initial water abundances,atmospheres with several thousands of bars of O 2 are possible. A substantial steam envelope would indicate either the existence of an earlier H 2 envelope or low XUV flux over the system's lifetime. A steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132b. Further modeling is needed to study the evolution of CO 2 or N 2 -rich atmospheres on GJ 1132b.

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Section: Predictions For Gj 1132bmentioning

confidence: 99%

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

Schaefer

Wordsworth²,

Berta-Thompson

et al. 2016

ApJ

167

279

View full text Add to dashboard Cite

show abstract

“…Given that sensitive atmospheric observations will likely require many transits to build sufficient signal (e.g., Cowan et al 2015), we have used a metric that optimizes the S/N over a period of time rather than a per-transit metric. Out of this sample of super-Earth exoplanets, all three planets in the GJ9827 system are in the top 20 in terms of the S/N for atmospheric characterization.…”

Section: Prospects For Atmospheric Characterizationmentioning

confidence: 99%

Three Super-Earths Transiting the Nearby Star GJ 9827

Niraula

Redfield

Dai

et al. 2017

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We report on the discovery of three transiting planets around GJ9827. The planets have radii of 1.75±0.18, 1.36±0.14, and 2.11 0.21 0.22 -+ R ⊕ , and periods of 1.20896, 3.6480, and 6.2014 days, respectively. The detection was made in Campaign 12 observations as part of our K2 survey of nearby stars. GJ9827 is a V=10.39 mag K6V star at a distance of 30.3±1.6 parsecs and the nearest star to be found hosting planets by Kepler and K2. The radial velocity follow-up, high-resolution imaging, and detection of multiple transiting objects near commensurability drastically reduce the false positive probability. The orbital periods of GJ9827b, c, and d planets are very close to the 1:3:5 mean motion resonance. Our preliminary analysis shows that GJ9827 planets are excellent candidates for atmospheric observations. Besides, the planetary radii span both sides of the rocky and gaseous divide, hence the system will be an asset in expanding our understanding of the threshold.

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“…The idea is to illustrate the connection between climate and observables rather than to prepare the characterization of Earth-like planets around Sunlike stars as no forthcoming instrument will be able to provide such data. The James Webb Space Telescope (JWST), on the other hand, may be able to obtain (at a large observing-time cost) some data for terrestrial HZ planets around cool host-dwarfs (Cowan et al 2015;Triaud et al 2013;Belu et al 2013). However, as before, without accounting for the actual spectral distribution of the host, which will be the object of a future study, the generated signatures of planets around M stars and brown dwarfs would not be realistic.…”

Section: Observablesmentioning

confidence: 99%

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

Bolmont

Libert

Leconte

et al. 2016

A&A

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Unlike the Earth, which has a small orbital eccentricity, some exoplanets discovered in the insolation habitable zone (HZ) have high orbital eccentricities (e.g., up to an eccentricity of ∼0.97 for HD 20782 b). This raises the question of whether these planets have surface conditions favorable to liquid water. In order to assess the habitability of an eccentric planet, the mean flux approximation is often used. It states that a planet on an eccentric orbit is called habitable if it receives on average a flux compatible with the presence of surface liquid water. However, because the planets experience important insolation variations over one orbit and even spend some time outside the HZ for high eccentricities, the question of their habitability might not be as straightforward. We performed a set of simulations using the global climate model LMDZ to explore the limits of the mean flux approximation when varying the luminosity of the host star and the eccentricity of the planet. We computed the climate of tidally locked ocean covered planets with orbital eccentricity from 0 to 0.9 receiving a mean flux equal to Earth's. These planets are found around stars of luminosity ranging from 1 L to 10 −4 L . We use a definition of habitability based on the presence of surface liquid water, and find that most of the planets considered can sustain surface liquid water on the dayside with an ice cap on the nightside. However, for high eccentricity and high luminosity, planets cannot sustain surface liquid water during the whole orbital period. They completely freeze at apoastron and when approaching periastron an ocean appears around the substellar point. We conclude that the higher the eccentricity and the higher the luminosity of the star, the less reliable the mean flux approximation.

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Characterizing Transiting Planet Atmospheres through 2025

Cited by 139 publications

References 140 publications

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

Three Super-Earths Transiting the Nearby Star GJ 9827

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

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