I am an associate astronomer at the Shanghai Astronomical Observatory, Chinese Academy of Sciences, a position I have held since January 2023. As a member of the Planetary Physics and Magnetohydrodynamic Research Group, I specialize in theoretical astrophysics and apply physical laws to gain insights into various astronomical phenomena.
My primary research focus is on the physics and chemistry of the middle and upper atmospheres of gas giant exoplanets, as well as their escape mechanism, through both observational analysis and theoretical modeling. Additionally, I have developed the interior structure model, MAGRATHEA, to provide valuable constraints on the compositions of terrestrial exoplanets. Furthermore, I have written a radiative transfer model to explore the physics of interacting supernova remnants.
Prior to joining SHAO, I completed two postdoctoral programs. From September 2017 to August 2019, I collaborated with Prof. Jason Steffen at UNLV. Subsequently, from August 2019 to October 2022, I worked alongside Prof. Tommi Koskinen at the Lunar and Planetary Laboratory, University of Arizona.
In 2017, I received my Ph.D. in Astronomy from UVa, under the mentorship of Prof. Phil Arras and Prof. Roger Chevalier. My doctoral research extensively focused on theoretical studies of exoplanet atmospheres and supernova remnants. Earlier, in 2011, I obtained my B.S. in Physics from Peking University.
Collaborate with Tommi Koskinen, we expand the Adding atomic metal species and related physical processes into the photochemical-dynamical thermosphere in Koskinen et al., 2013, Koskinen and I try to interpret the observed transmission spectrum of metal species in NUV.
Under the supervision of Phil Arras at UVa, we constructed a hot Jupiter thermosphere model to explain the observed Hα and Na D transmission spectrum of HD 189733b and constrain the properties of hot Jupiter upper atmosphere (Huang et al., 2017). We demonstrate that radiative excitation by Lyα is the dominant mechanism for H atom excitation, and constructed a Monte Carlo simulation for the resonant scattering process of Lyα photon in the upper atmosphere.
Under the supervision of Roger Chevalier at UVa, we constructed a model of radiation transfer due to electron scattering within pre-shocked ionized circumstellar medium (CSM) to explain the observed broad component of interacting supernovae emission lines (Huang & Chevalier, 2018).
Under the direction of Jason Steffen at UNLV and collaborate with David Rice, we develope an open-source C++ terrestrial planet interior structure code MAGRATHEA. The code is structured to enable the user to choose between a large library of EOSs and add/change materials and equations (Huang et al., 2022, submitted). Using MAGRATHEA, we demonstrate the effect of the new measurement of equation of state (EOS) of water ice on our understanding of terrestrial planets (Huang et al., 2021).
, the atmosphere blocks an extra amount of the light. The scale of the brightness reduction at frequency ν due to planet and its atmosphere is equivalent to a bare planet with an equivalent radius of
. Because the opacity of molecules and atoms in a planet's atmosphere is a function of wavelength, they will leave their trace in the transmission spectrum. Transmission spectrum is the best tool to characterize the atmosphere near the planet's terminator.
Following Christie et al. 2013, we constructed a spherically symmetric hydrostatic atmosphere model encompassing the region dominated by atomic hydrogen. The atomic hydrogen level population was computed including both collisional and radiative transition rates. The radiative rates between 1s and 2p determines throughout the simulation domain because of the large Lyα intensity
. Lyα may also play a role in the heating/cooling and ionization/recombination balance, so a detailed Lyα radiation transfer calculation is crucial.
We solved the Lyα resonant scattering numerically with the Monte-Carlo method, illustrated in Figure 2. The run of particle densities and temperatures versus radius from the hydrostatic atmosphere calculation were used to specify the Lyα source function, as well as the mean free path to scattering and true absorption. Both the incident stellar Lyα and internal sources due to recombination cascade and collisional excitation were included. The hydrostatic atmosphere and Lyα radiation transfer simulation were done iteratively until the result converges.
and increasing
with depth gives rise to an approximately flat H(n=2) around 104 cm-3 over two decades in pressure near the base of the thermosphere, where the temperature is in the range 3000 ~ 6000 K. Metal species, esp. Mg, Na, and Si, are important in heating and cooling of this region. The number densities of Na I and H(n=2) are similar in the pressure region near 10-2 μbar, where the optical depths of Na D and Hα reach 1. This leads to similar transit depths for observed Hα and Na D lines.
Using the temperature and number density of H(n=2) and Na I at each radius, the transmission spectra of Hα (Figure 4) and Na D (Figure 5) we obtained are in broad agreement with the observations of HD 189733b.
The host star of the planet, HD 189733, is a 8 magnitude star in the constellation of Vulpecula, located near the center of the summer triangle. It can be found with binoculars 0.3 degrees east of the Dumbbell Nebula. The brightness and location of the star make it a ideal target for amateur telescope. Photo: I was observing the HD 189733 using the 26-inch refractor telescope located at the McCormick observatory. It is an interesting experience to have the chance to directly see the system that I am studying.
Shown in Figure 6, the Monte-Carlo simulations were carried out in spherical symmetry, with the scattering medium between the absorbing inner boundary (R1), which can represent a shocked shell, and a large escaping outer radius (R2), which stands for the outer boundary of ionized dense CSM. A photon generated in the wind gas can a) be absorbed by the inner boundary, b) escape the medium from the outer boundary without any scattering, contributing to the narrow component of the spectrum, or c) escape from the outer boundary after scattering a certain number of times, contributing to the broad component.
The black body continuum subtracted SN 2011ht Hα spectrum (black line in Figure 7) shows a narrow component and a broad component with an enhanced red wing (note the exponential y-scale). It can be explained with a model (red line) of expanding CSM with electron scattering optical depth of τ=3.5, temperature of 12,000 K and expanding velocity 600 km/s. A broad He emission feature creates the bump on the red wing around 5000 km/s.
Terrestrial planets may be essential to life because of their solid or liquid surfaces. Interior structure models estimate the radius of terrestrial planets with given masses and compositions. Such models are important in several ways. For example, for planets whose mass and radius are well determined through observation, their interior structure and composition can be roughly constrained by comparing observed values with planet model. Planet interior structure also determines the tidal energy dissipation rate of planets, which is required to study the dynamical and tidal evolution of close-packed planetary systems, such as TRAPPIST-1. Additionally, the late stage of planet formation involves extensive collisions between Mars-sized embryos, which is typically modeled through N-body simulations. The collision timescale, is dependent on the embryo radii.
Solving the structure requires knowledge of the phase diagram and equation of state (EOS) ρ(P,T) for each material under high pressure. Compared to other codes, MAGRATHEA features phase diagram options and transparent EOS formatting, which enables the user to choose between a large library of EOSs and add/change materials and equations. We are motivated by our collaboration with high-pressure physicists at UNLV, who significantly improved the measurement accuracy of the phase diagram and EOS of water ice. Using MAGRATHEA, we study how uncertainties in experimental EOSs affect predictions of planet interiors.
