A new class of Super-Earths formed from high-temperature condensates: HD219134 b, 55 Cnc e, WASP-47 e

Dorn, Caroline; Harrison, John; Bonsor, Amy; Hands, Thomas

doi:10.1093/mnras/sty3435

Cited by 99 publications

(90 citation statements)

References 97 publications

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“…This raises the question of whether mass-radius data can be explained by differences in the phase of silicate matter, rather than invoking bulk compositions that depart strongly from Earth (e.g. Dorn et al 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Dorn et al 2018). Additional data or modelling constraints can be used to limit the range of acceptable interior structures, such as a combination of stellar abundances (Dorn et al 2016) and disk evolution models (Dorn et al 2019). Ordinarily, static structure models assume an interior thermal structure, although this is adopted a priori rather than relating directly to evolutionary considerations.…”

Section: Introductionmentioning

confidence: 99%

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Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

Bower

Kitzmann

Wolf

et al. 2019

A&A

107

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Context. A terrestrial planet is molten during formation and may remain molten due to intense insolation or tidal forces. Observations favour the detection and characterisation of hot planets, potentially with large outgassed atmospheres. Aims. We aim to determine the radius of hot Earth-like planets with large outgassing atmospheres. Our goal is to explore the differences between molten and solid silicate planets on the mass–radius relationship and transmission and emission spectra. Methods. An interior–atmosphere model was combined with static structure calculations to track the evolving radius of a hot rocky planet that outgasses CO2 and H2O. We generated synthetic emission and transmission spectra for CO2 and H2O dominated atmospheres. Results. Atmospheres dominated by CO2 suppress the outgassing of H2O to a greater extent than previously realised since previous studies applied an erroneous relationship between volatile mass and partial pressure. We therefore predict that more H2O can be retained by the interior during the later stages of magma ocean crystallisation. Formation of a surface lid can tie the outgassing of H2O to the efficiency of heat transport through the lid, rather than the radiative timescale of the atmosphere. Contraction of the mantle, as it cools from molten to solid, reduces the radius by around 5%, which can partly be offset by the addition of a relatively light species (e.g. H2O versus CO2) to the atmosphere. Conclusions. A molten silicate mantle can increase the radius of a terrestrial planet by around 5% compared to its solid counterpart, or equivalently account for a 13% decrease in bulk density. An outgassing atmosphere can perturb the total radius, according to its composition, notably the abundance of light versus heavy volatile species. Atmospheres of terrestrial planets around M-stars that are dominated by CO2 or H2O can be distinguished by observing facilities with extended wavelength coverage (e.g. JWST).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

Bower

Kitzmann

Wolf

et al. 2019

A&A

107

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“…For planets with enough heat from stellar irradiation, inductive heating, or tidal forces, for example, an active mantle can prevail that causes active surface processing, such as volcanism or plate tectonics. Planetary structure modelling suggests that hot super-Earths, such as 55 Cnc e, have high atmospheric abundances of refractory elements, such as Ca and Al (Dorn et al 2019). These atmospheres are shown to allow the formation of mineral clouds (Mahapatra et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The atmospheres of rocky exoplanets

Herbort

Woitke

Helling

et al. 2020

A&A

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Context. Little is known about the interaction between atmospheres and crusts of exoplanets so far, but future space missions and ground-based instruments are expected to detect molecular features in the spectra of hot rocky exoplanets. Aims. We aim to understand the composition of the gas in an exoplanet atmosphere which is in equilibrium with a planetary crust. Methods. The molecular composition of the gas above a surface made of a mixture of solid and liquid materials was determined by assuming phase equilibrium for given pressure, temperature, and element abundances. We study total element abundances that represent different parts of the Earth’s crust (continental crust, bulk silicate Earth, mid oceanic ridge basalt), CI chondrites and abundances measured in polluted white dwarfs. Results. For temperatures between ~600 and ~3500 K, the near-crust atmospheres of all considered total element abundances are mainly composed of H2O, CO2, and SO2 and in some cases of O2 and H2. For temperatures ≲500 K, only N2-rich or CH4-rich atmospheres remain. For ≳3500 K, the atmospheric gas is mainly composed of atoms (O, Na, Mg, and Fe), metal oxides (SiO, NaO, MgO, CaO, AlO, and FeO), and some metal hydroxides (KOH and NaOH). The inclusion of phyllosilicates as potential condensed species is crucial for lower temperatures, as they can remove water from the gas phase below about 700 K and inhibit the presence of liquid water. Conclusions. Measurements of the atmospheric composition could, in principle, characterise the rock composition of exoplanet crusts. H2O, O2 and CH4 are natural products from the outgassing of different kinds of rocks that had time to equilibrate. These are discussed as biomarkers, but they do emerge naturally as a result of the thermodynamic interaction between the crust and atmosphere. Only the simultaneous detection of all three molecules might be a sufficient biosignature, as it is inconsistent with chemical equilibrium.

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“…Planets with radii 2 R ⊕ typically have densities which imply they have a composition similar to Earth (e.g. Dressing et al 2015;Dorn et al 2019). Whereas larger planets have lower densities, implying that they must contain a significant fraction of volatiles (e.g.…”

Section: Introductionmentioning

confidence: 99%

Testing exoplanet evaporation with multitransiting systems

Owen

Estrada

2019

Monthly Notices of the Royal Astronomical Society

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The photoevaporation model is one of the leading explanations for the evolution of small, close-in planets and the origin of the radius-valley. However, without planet mass measurements, it is challenging to test the photoevaporation scenario. Even if masses are available for individual planets, the host star's unknown EUV/X-ray history makes it difficult to assess the role of photoevaporation. We show that systems with multiple transiting planets are the best in which to rigorously test the photoevaporation model. By scaling one planet to another in a multi-transiting system, the host star's uncertain EUV/X-ray history can be negated. By focusing on systems that contain planets that straddle the radius-valley, one can estimate the minimum-masses of planets above the radius-valley (and thus are assumed to have retained a voluminous hydrogen/helium envelope). This minimum-mass is estimated by assuming that the planet below the radius-valley entirely lost its initial hydrogen/helium envelope, then calculating how massive any planet above the valley needs to be to retain its envelope. We apply this method to 104 planets above the radius gap in 73 systems for which precise enough radii measurements are available. We find excellent agreement with the photoevaporation model. Only two planets (Kepler -100c & 142c) appear to be inconsistent, suggesting they had a different formation history or followed a different evolutionary pathway to the bulk of the population. Our method can be used to identify TESS systems that warrant radial-velocity follow-up to further test the photoevaporation model.The software to estimate minimum planet masses is publicly available at: https://github.com/jo276/EvapMass

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A new class of Super-Earths formed from high-temperature condensates: HD219134 b, 55 Cnc e, WASP-47 e

Cited by 99 publications

References 97 publications

Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

The atmospheres of rocky exoplanets

Testing exoplanet evaporation with multitransiting systems

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