Li Zeng

Li Zeng
Harvard University | Harvard · Department of Earth and Planetary Sciences

Ph.D., M.A., B.S.

About

31
Publications
4,577
Reads
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1,269
Citations
Introduction
As Simons Postdoctoral Fellow in the Department of Earth and Planetary Sciences at Harvard University, I have been working with my mentor Professor Stein B. Jacobsen and my former PhD advisor Professor Dimitar D. Sasselov on interior structure, chemistry, and evolution of solid exoplanets.
Additional affiliations
June 2015 - present
Harvard University
Position
  • Simons Postdoctoral Fellow
Description
  • Simons Postdoctoral Fellow (Simons Collaboration on the Origins of Life) Research focus on Interior Structure, Chemistry, and Evolution of Earth-like Solid Exoplanets.
January 2012 - May 2012
Harvard University
Position
  • Head of Department
Description
  • Harvard Undergraduate General Education Course: “Science of the Physical Universe 30: Life as a Planetary Phenomenon”. Instructor: Dimitar Sasselov.
January 2011 - May 2011
Harvard University
Position
  • Professor
Description
  • Harvard Undergraduate General Education Course: “Science of the Physical Universe 30: Life as a Planetary Phenomenon”. Instructor: Dimitar Sasselov.
Education
July 2009 - May 2011
Harvard University
Field of study
  • Astronomy & Astrophysics
July 2009 - May 2015
Harvard University
Field of study
  • Astronomy & Astrophysics
August 2006 - June 2009

Publications

Publications (31)
Preprint
Full-text available
We present the detection of neutral helium at 10833A in the atmosphere of WASP-52b and tentative evidence of helium in the atmosphere of the grazing WASP-177b, using high-resolution observations acquired with the NIRSPEC instrument on the Keck II telescope. We detect excess absorption by helium in WASP-52b's atmosphere of $3.44 \pm 0.31$% ($11\sigm...
Article
We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars observed with HARPS-N and K2. Their respective 10.99 day and 15.39 day orbital periods fall near periods of signals induced by stellar magnetic activity. The two signals might therefore interfere and lead to an inaccurate estimate o...
Preprint
Full-text available
Recent astronomical observations obtained with the Kepler and TESS missions and their related ground-based follow-ups revealed an abundance of exoplanets with a size intermediate between Earth and Neptune. A low occurrence rate of planets has been identified at around twice the size of Earth, known as the exoplanet radius gap or radius valley. We e...
Article
Full-text available
Recent astronomical observations obtained with the Kepler and TESS missions and their related ground-based follow-ups revealed an abundance of exoplanets with a size intermediate between Earth and Neptune (1 R ⊕ ≤ R ≤ 4 R ⊕ ). A low occurrence rate of planets has been identified at around twice the size of Earth (2 × R ⊕ ), known as the exoplanet r...
Preprint
Full-text available
We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars. Their respective 10.99d and 15.39d orbital periods fall near periods of signals induced by stellar magnetic activity. The two signals might therefore interfere and lead to an inaccurate estimate of exoplanet mass. We present a meth...
Preprint
Although several thousands of exoplanets have now been detected and characterized, observational biases have led to a paucity of long-period, low-mass exoplanets with measured masses and a corresponding lag in our understanding of such planets. In this paper we report the mass estimation and characterization of the long-period exoplanet Kepler-538b...
Preprint
The radii and orbital periods of 4000+ confirmed/candidate exoplanets have been precisely measured by the Kepler mission. The radii show a bimodal distribution, with two peaks corresponding to smaller planets (likely rocky) and larger intermediate-size planets, respectively. While only the masses of the planets orbiting the brightest stars can be d...
Article
Full-text available
Measures of exoplanet bulk densities indicate that small exoplanets with radius less than 3 Earth radii ($R_\oplus$) range from low-density sub-Neptunes containing volatile elements to higher density rocky planets with Earth-like or iron-rich (Mercury-like) compositions. Such astonishing diversity in observed small exoplanet compositions may be the...
Article
The radii and orbital periods of 4,000+ confirmed/candidate exoplanets have been precisely measured by the Kepler mission. The radii show a bimodal distribution, with two peaks corresponding to smaller planets (likely rocky) and larger intermediate-size planets, respectively. While only the masses of the planets orbiting the brightest stars can be...
Preprint
Applying the survival function analysis to the planet radius distribution of the Kepler confirmed/candidate planets, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 Earth radii separates small exoplane...
Article
Full-text available
Some seismic models derived from tomographic studies indicate elevated shear‐wave velocities (≥4.7 km/s) around 120‐150 km depth in cratonic lithospheric mantle. These velocities are higher than those of cratonic peridotites, even assuming a cold cratonic geotherm (i.e., 35 mW/m2 surface heat flux) and accounting for compositional heterogeneity in...
Preprint
Full-text available
The size distribution of exoplanets is a bimodal division into two groups: Rocky planet (<2 Earth radii) and water-rich planet (>2 Earth radii) with or without gaseous envelope.
Article
Full-text available
Applying survival function analysis to planet orbital period and semi-major axis distribution from the Kepler sample, we found that all exoplanets are uniformly distributed in (Log a) or (Log P), where a is the orbit semi-major axis and P is orbital period, with an inner cut-off of closest distance to the host star. This inner cut-off is 0.04 AU fo...
Article
Full-text available
Applying survival function analysis to the planet radius distribution from the Kepler sample, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 R separates small exoplanets from the ones above. When comb...
Article
Full-text available
Exoplanets smaller than Neptune are numerous, but the nature of the planet populations in the 1-4 Earth radii range remains a mystery. The complete Kepler sample of Q1-Q17 exoplanet candidates shows a radius gap at ~ 2 Earth radii, as reported by us in January 2017 in LPSC conference abstract #1576 (Zeng et al. 2017). A careful analysis of Kepler h...
Article
HD 179070, aka Kepler-21, is a V = 8.25 F6IV star and the brightest exoplanet host discovered by Kepler. An early detailed analysis by Howell et al. (2012) of the first thirteen months (Q0 - Q5) of Kepler light curves revealed transits of a planetary companion, Kepler-21b, with a radius of about 1.60 +/- 0.04 R_earth and an orbital period of about...
Article
In the past few years, the number of confirmed planets has grown above 2000. It is clear that they represent a diversity of structures not seen in our own solar system. In addition to very detailed interior modeling, it is valuable to have a simple analytical framework for describing planetary structures. Variational principle is a fundamental prin...
Article
Based on the PREM~\citep{Dziewonski:1981}, the internal gravity of the Earth increases approximately linearly in the core and stays approximately constant in the mantle. Tested with numerical calculations in~\citet{Zeng:2016}, this behavior of internal gravity can be generalized to any two-layer (iron-silicate) rocky exoplanet with core mass fracti...
Article
Full-text available
Several small dense exoplanets are now known, inviting comparisons to Earth and Venus. Such comparisons require translating their masses and sizes to composition models of evolved multi-layer-interior planets. Such theoretical models rely on our understanding of the Earth's interior, as well as independently derived equations of state (EOS), but ha...
Code
★Manipulate Planet characterizes and illustrates the interior structure of planets based on the extrapolation of Earth’s Seismic Density Profile (PREM). Require Wolfram CDF player. (updated 2015/12) If the tool fails to load in any other web browser, try open it in Firefox. ★Please cite the following papers: “Mass-Radius Relation for Rocky Planets...
Article
Full-text available
We report the first planet discovery from the two-wheeled Kepler (K2) mission: HIP 116454 b. The host star HIP 116454 is a bright (V = 10.1, K = 8.0) K1-dwarf with high proper motion, and a parallax-based distance of 55.2 +/- 5.4 pc. Based on high-resolution optical spectroscopy, we find that the host star is metal-poor with [Fe/H] = -.16 +/- .18,...
Article
Full-text available
We present the characterization of the Kepler-93 exoplanetary system, based on three years of photometry gathered by the Kepler spacecraft. The duration and cadence of the Kepler observations, in tandem with the brightness of the star, enable unusually precise constraints on both the planet and its host. We conduct an asteroseismic analysis of the...
Article
Full-text available
For most planets in the range of radii from 1 to 4 R ?, water is a major component of the interior composition. At high pressure H2O can be solid, but for larger planets, like Neptune, the temperature can be too high for this. Mass and age play a role in determining the transition between solid and fluid (and mixed) water-rich super-Earth. We use t...
Article
Full-text available
This paper describes a new grid for the mass-radius relation of 3-layer exoplanets within the mass range of 0.1 through 100 Earth Masses. The 3 layers are: Fe (epsilon iron), MgSiO3 (including both the perovskite phase, post-perovskite phase, and its dissociation at ultra-high pressures), and H2O (including Ices Ih, III, V, VI, VII, X, and the supe...
Article
Full-text available
The prospects for finding transiting exoplanets in the range of a few to 20 Earth masses is growing rapidly with both ground-based and spaced-based efforts. We describe a publicly available computer code to compute and quantify the compositional ambiguities for differentiated solid exoplanets with a measured mass and radius, including the mass and...

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