Haiyang Wang

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Wang

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Haiyang

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0000-0001-8618-3343

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Publications1 - 10 of 20

Large Interferometer For Exoplanets (LIFE)
Cesario, Lorenzo; Lichtenberg, Tim; Alei, Eleonora; et al. (2024)
Astronomy & Astrophysics
Context: The increased brightness temperature of young rocky protoplanets during their magma ocean epoch makes them potentially amenable to atmospheric characterization at distances from the Solar System far greater than thermally equilibrated terrestrial exoplanets, offering observational opportunities for unique insights into the origin of secondary atmospheres and the near surface conditions of prebiotic environments. Aims: The Large Interferometer For Exoplanets (LIFE) mission will employ a space-based midinfrared nulling interferometer to directly measure the thermal emission of terrestrial exoplanets. In this work, we seek to assess the capabilities of various instrumental design choices of the LIFE mission concept for the detection of cooling protoplanets with transient high-temperature magma ocean atmospheres at the tail end of planetary accretion. In particular, we investigate the minimum integration times necessary to detect transient magma ocean exoplanets in young stellar associations in the Solar neighborhood. Methods: Using the LIFE mission instrument simulator (LIFEsim), we assessed how specific instrumental parameters and design choices, such as wavelength coverage, aperture diameter, and photon throughput, facilitate or disadvantage the detection of protoplan-ets. We focused on the observational sensitivities of distance to the observed planetary system, protoplanet brightness temperature (using a blackbody assumption), and orbital distance of the potential protoplanets around both G- and M-dwarf stars. Results: Our simulations suggest that LIFE will be able to detect (S/N ≥ 7) hot protoplanets in young stellar associations up to distances of 100 pc from the Solar System for reasonable integration times (up to a few hours). Detection of an Earth-sized protoplanet orbiting a Solar-sized host star at 1 AU requires less than 30 minutes of integration time. M-dwarfs generally need shorter integration times. The contribution from wavelength regions smaller than 6 µm is important for decreasing the detection threshold and discriminating emission temperatures. Conclusions: The LIFE mission is capable of detecting cooling terrestrial protoplanets within minutes to hours in several local young stellar associations hosting potential targets. The anticipated compositional range of magma ocean atmospheres motivates further architectural design studies to characterize the crucial transition from primary to secondary atmospheres.
The PLATO mission
Rauer, Heike; Aerts, Conny; Cabrera, Juan; et al. (2025)
Experimental Astronomy
PLATO (PLAnetary Transits and Oscillations of stars) is ESA’s M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2REarth) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO‘s target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.
A model Earth-sized planet in the habitable zone of α Centauri A/B
Wang, Haiyang; Linweaver, Charles; Quanz, Sascha Patrick; et al. (2022)
The Astrophysical Journal
The bulk chemical composition and interior structure of rocky exoplanets are of fundamental importance to understanding their long-term evolution and potential habitability. Observations of the chemical compositions of the solar system rocky bodies and of other planetary systems have increasingly shown a concordant picture that the chemical composition of rocky planets reflects that of their host stars for refractory elements, whereas this expression breaks down for volatiles. This behavior is explained by devolatilization during planetary formation and early evolution. Here, we apply a devolatilization model calibrated with the solar system bodies to the chemical composition of our nearest Sun-like stars -- α Centauri A and B -- to estimate the bulk composition of any habitable-zone rocky planet in this binary system ("α-Cen-Earth"). Through further modeling of likely planetary interiors and early atmospheres, we find that compared to Earth, such a planet is expected to have (i) a reduced (primitive) mantle that is similarly dominated by silicates albeit enriched in carbon-bearing species (graphite/diamond); (ii) a slightly larger iron core, with a core mass fraction of 38.4+4.7−5.1 wt% (cf. Earth's 32.5 ± 0.3 wt%); (iii) an equivalent water-storage capacity; and (iv) a CO2-CH4-H2O-dominated early atmosphere that resembles that of Archean Earth. Further taking into account its ∼ 25% lower intrinsic radiogenic heating from long-lived radionuclides, an ancient α-Cen-Earth (∼ 1.5-2.5 Gyr older than Earth) is expected to have less efficient mantle convection and planetary resurfacing, with a potentially prolonged history of stagnant-lid regimes.
Plausible Constraints on the Range of Bulk Terrestrial Exoplanet Compositions in the Solar Neighborhood
Spaargaren, Rob J.; Wang, Haiyang; Mojzsis, Stephen; et al. (2023)
The Astrophysical Journal
Rocky planet compositions regulate planetary evolution by affecting core sizes, mantle properties, and melting behaviors. Yet, quantitative treatments of this aspect of exoplanet studies remain generally underexplored. We attempt to constrain the range of potential bulk terrestrial exoplanet compositions in the solar neighborhood (<200 pc). We circumscribe probable rocky exoplanet compositions based on a population analysis of stellar chemical abundances from the Hypatia and GALAH catalogs. We apply a devolatilization model to simulate compositions of hypothetical, terrestrial-type exoplanets in the habitable zones around Sun-like stars, considering elements O, S, Na, Si, Mg, Fe, Ni, Ca, and Al. We further apply core-mantle differentiation by assuming constant oxygen fugacity, and model the consequent mantle mineralogy with a Gibbs energy minimization algorithm. We report statistics on several compositional parameters and propose a reference set of (21) representative planet compositions for use as end-member compositions in imminent modeling and experimental studies. We find a strong correlation between stellar Fe/Mg and metallic-core sizes, which can vary from 18 to 35 wt%. Furthermore, stellar Mg/Si gives a first-order indication of mantle mineralogy, with high-Mg/Si stars leading to weaker, ferropericlase-rich mantles, and low-Mg/Si stars leading to mechanically stronger mantles. The element Na, which modulates crustal buoyancy and mantle clinopyroxene fraction, is affected by devolatilization the most. While we find that planetary mantles mostly consist of Fe/Mg silicates, the core sizes and relative abundances of common minerals can nevertheless vary significantly among exoplanets. These differences likely lead to different evolutionary pathways among rocky exoplanets in the solar neighborhood.
Large Interferometer for Exoplanets: VIII. Where Is the Phosphine? Observing Exoplanetary PH3 with a Space Based Mid-Infrared Nulling Interferometer
Angerhausen, Daniel; Ottiger, Maurice; Dannert, Felix; et al. (2023)
Astrobiology
Phosphine could be a key molecule in the understanding of exotic chemistry that occurs in (exo)planetary atmospheres. While phosphine has been detected in the Solar System's giant planets, it has not been observed in exoplanets to date. In the exoplanetary context, however, it has been theorized to be a potential biosignature molecule. The goal of our study was to identify which illustrative science cases for PH3 chemistry are observable with a space-based mid-infrared nulling interferometric observatory like the Large Interferometer for Exoplanets (LIFE) concept. We identified a representative set of scenarios for PH3 detections in exoplanetary atmospheres that vary over the whole dynamic range of the LIFE mission. We used chemical kinetics and radiative transfer calculations to produce forward models of these informative, prototypical observational cases for LIFEsim, our observation simulator software for LIFE. In a detailed, yet first order approximation, it takes a mission like LIFE: (i) about 1 h to find phosphine in a warm giant around a G star at 10 pc, (ii) about 10 h in H-2 or CO2 dominated temperate super-Earths around M star hosts at 5 pc, (iii) and even in 100 h it seems very unlikely that phosphine would be detectable in a Venus-Twin with extreme PH3 concentrations at 5 pc. Phosphine in concentrations previously discussed in the literature is detectable in 2 out of the 3 cases, and it is detected about an order of magnitude faster than in comparable cases with James Webb Space Telescope. We show that there is a significant number of objects accessible for these classes of observations. These results will be used to prioritize the parameter range for the next steps with more detailed retrieval simulations. They will also inform timely questions in the early design phase of a mission like LIFE and guide the community by providing easy-to-scale first estimates for a large part of detection space of such a mission.
Reasoning the chemical composition and geological evolution of terrestrial planets to be found in the Alpha Centauri A and B System: A top-down approach
Wang, Haiyang; Lineweaver, Charles; Mojzsis, Stephen; et al. (2021)
Europium as a lodestar: diagnosis of radiogenic heat production in terrestrial exoplanets
Wang, Haiyang; Morel, Thierry; Quanz, Sascha Patrick; et al. (2020)
Astronomy & Astrophysics
Context. Long-lived radioactive nuclides, such as 40K, 232Th, 235U, and 238U, contribute to persistent heat production in the mantle of terrestrial-type planets. As refractory elements, the concentrations of Th and U in a terrestrial exoplanet are implicitly reflected in the photospheric abundances of the stellar host. However, a robust determination of these stellar abundances is difficult in practice owing to the general paucity and weakness of the relevant spectral features. Aims. We draw attention to the refractory, r-process element europium, which may be used as a convenient and practical proxy for the population analysis of radiogenic heating in exoplanetary systems. Methods. As a case study, we present a determination of Eu abundances in the photospheres of α Cen A and B with high-resolution HARPS spectra and a strict line-by-line differential analysis. To first order, the measured Eu abundances can be converted into the abundances of 232Th, 235U, and 238U with observational constraints, while the abundance of 40K is approximated independently with a Galactic chemical evolution model. Results. Our determination shows that europium is depleted with respect to iron by ~0.1 dex and to silicon by ~0.15 dex compared to solar in the two binary components. The loci of α Cen AB at the low-ends of both [Eu/Fe] and [Eu/Si] distributions of a large sample of FGK stars further suggest significantly lower potential of radiogenic heat production in any putative terrestrial-like planet (i.e. α-Cen-Earth) in this system compared to that in rocky planets (including our own Earth) that formed around the majority of these Sun-like stars. Based on our calculations of the radionuclide concentrations in the mantle and assuming the mantle mass to be the same as that of our Earth, we find that the radiogenic heat budget in an α-Cen-Earth is 73.4−6.9+8.3 TW upon its formation and 8.8−1.3+1.7 TW at the present day, which is 23 ± 5% and 54 ± 5% lower than that in the Hadean Earth (94.9 ± 5.5 TW) and in the modern Earth (19.0 ± 1.1 TW), respectively. Conclusions. As a consequence, mantle convection in an α-Cen-Earth is expected to be overall weaker than that of Earth (assuming other conditions are the same), and thus such a planet would be less geologically active, suppressing its long-term potential to recycle its crust and volatiles. With Eu abundances being available for a large sample of Sun-like stars, the proposed approach can extend our ability to predict the nature of other rocky worlds that can be tested by future observations. © ESO 2020.
No universal devolatilization trend has been found for the solar system rocky bodies
Lin, Wen-Jou; Wang, Haiyang; Hunt, Alison; et al. (2022)
EPSC Abstracts
Rocky planets formed at different heliocentric distances from the Sun are thought to experience different and systematic devolatilization (i.e. depletion of volatile elements) with respect to the solar composition. The canonical empirical model of devolatilization is calibrated based on the bulk compositional difference between the Sun and Earth as a function of 50% condensation temperature of elements (TC). The quantification of the volatility trends for other solar system rocky bodies, with a goal of formulating a general devolatilization model, has been expected to be useful for estimating the bulk compositions of rocky exoplanets orbiting at different distances to the central star in a planetary system. To do so, we compiled an enormous set of literature data for the bulk compositions of a wide range of rocky bodies in our Solar System, including the terrestrial planets, asteroids, and chondritic bodies. Following the previous studies on quantifying Earth’s volatility trends, we adopted two relationship forms: one is in the log-log space (log (f) = α log (TC) + β, where f is the bulk compositional ratio of a rocky body relative to the Sun; α and β are the model coefficients); and the other is in the linear space (f = 1/(1+e-k(T-T0)), where T is the mid-plane temperature assuming the in-situ formation of these planetary bodies; and k and T0 are the model coefficients). Based on the best literature data that have been compiled, we did not find any statistically robust trend of devolatilization for these rocky bodies, except for Earth and Mars. If we arbitrarily increase the uncertainties of the coefficients of the poorly quantified volatility trends for Venus and Mercury by a factor of 3, the best possible general trend that we can quantify as a function of heliocentric distance (d) is α = (3.773 ± 0.202)/d3/4 and β = (-11.832 ± 0.613)/d3/4. However, Mercury is still statistically deviated (towards a larger slope and thus severer devolatilization) from the general trend. We find the similar behaviour if we adopt the alternative sigmoid function. This may imply a more violent thermal history that Mercury experienced during its formation, beyond what can be constrained with the assumptions of the in-situ formation and stellar-irradiation-relevant-only devolatilization. Furthermore, Vesta and ordinary and carbonaceous chondrites do not follow this nominal general trend, either. We therefore report here that no universal devolatilization trend has been found (empirically) for the solar system rocky bodies. This null result warrants the future efforts in advancing this field on two fundamental aspects. One is to further improve the measurements of the compositions of the solar system objects through various missions. The other is to launch a comprehensive investigation of nebular condensation, disc evolution, hydrodynamic escape, accretionary dynamics, and impacts towards establishing a sophisticated planet formation model of both dynamics and chemistry.
Extrasolar Geochemistry: Predicting Rocky Exoplanet Mantle Mineralogy Using Stellar Abundance Data
Spaargaren, Rob; Wang, Haiyang; Mojzsis, Stephen; et al. (2024)
Goldschmidt 2024 Abstract
The interior diversity of terrestrial-type exoplanets: constrained with devolatilized stellar abundances and mass-radius measurements
Wang, Haiyang; Quanz, Sascha Patrick; Yong, David; et al. (2022)
EPSC Abstracts
A major goal in the discovery and characterization of exoplanets is to identify terrestrial-type worlds that are similar to (or otherwise distinct from) our Earth. The combination of mass-radius measurements and host stellar abundances has been proposed to constrain the interiors of small (rocky) exoplanets. In this work, we advocate the importance of using devolatilized stellar abundances, instead of uncorrected stellar abundances, to further reduce degeneracies in modelling the interiors of rocky exoplanets. We apply an empirical devolatilization model to a selected sample of 13 planet-hosting Sun-like stars, for which high-precision photospheric abundances have been available. With the resultant devolatilized stellar composition (i.e. the model planetary bulk composition), as well as other constraints including mass and radius, we model the detailed mineralogy and interior structure of hypothetical, habitable-zone terrestrial planets (‘exo-Earths’) around these stars. Model output shows that most of these exo-Earths are expected to have broadly Earth-like composition and interior structure, consistent with conclusions derived independently from analysis of polluted white dwarfs. Investigating the empirical devolatilization model at its extremes as well as varying planetary mass and radius (within the terrestrial regime) reveals potential diversities in the interiors of terrestrial planets. By considering (i) high-precision stellar abundances, (ii) devolatilization, and (iii) planetary mass and radius holistically, this work represents essential steps to explore the detailed mineralogy and interior structure of terrestrial-type exoplanets, which in turn are fundamental for a quantitative understanding of planetary long-term evolution including the interior-atmosphere interactions.

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