Jiayin Dong

  • Assistant Professor of Astronomy
I am an Assistant Professor of Astronomy at the University of Illinois Urbana-Champaign. My research integrates computational and statistical methods with observations to study the formation and evolution of planetary systems. I received my PhD in Astronomy and Astrophysics from Penn State University and was a Flatiron Research Fellow at the Center for Computational Astrophysics at the Flatiron Institute.
  • Stellar Obliquity Distribution of Hot Jupiters Dong & Foreman-Mackey 2023, AJ, 166, 112 Stellar obliquity, the angle between a planet's orbital axis and its host star's spin axis, serves as a probe of a planetary system's formation and dynamical history. Different high-e migration scenarios for Hot Jupiters predict different stellar obliquity distributions. In this population study, we found that the misaligned Hot Jupiter population follows a nearly isotropic distribution. This suggests that planet-planet interactions could be the primary channel for the formation of Hot Jupiters. We also introduce this population-level obliquity inference code that models the spin-orbit angle distribution of exoplanetary systems using a hierarchical Bayesian framework.
  • Eccentricity Distribution of TESS Warm Jupiters Dong, Huang, Dawson et al. 2021, ApJS, 255, 6
    Dong, Huang, Zhou et al. 2021, ApJL, 920, L16
    The formation process of Warm Jupiters remains unclear. They may form in situ, undergo disk or high eccentricity tidal migration, or be formed through a combination of these channels. Each of these origin theories leads to different expectations for the eccentricities of Warm Jupiters. We have been systematically searching for Warm Jupiters in the TESS Full-Frame Images and conducting follow-up observations. As a result of our research, we have introduced a catalog of Warm Jupiter candidates identified from the first year of TESS data. These Warm Jupiters have been validated and characterized based on their transit-timing variations and eccentricities. We have inferred their eccentricity distribution using hierarchical Bayesian modeling and found a broad and possibly bimodal eccentricity distribution of Warm Jupiters' orbits. This suggests Warm Jupiters, similar to Hot Jupiters, undergo planet-planet interactions. Our survey led to the discovery of TOI-3362b, a Jupiter-like planet with the highest observed eccentricity among planets with orbital periods less than 20 days. It is likely undergoing high-eccentricity tidal migration.
  • Rossiter-McLaughlin Measurements of Close-In Planets Dong, Wang, Rice et al. 2023, ApJL, 951, L29
    Dong, Huang, Zhou et al. 2022, ApJL, 920, L7     Warm Jupiters are close-in giant planets with relatively large planet-star separations. Their stellar obliquities are less influenced by planet-star tidal interactions and, therefore, may serve as a probe of the planetary system's formation and dynamical history. However, the stellar obliquities of Warm Jupiters have not been extensively explored, particularly for those with highly elliptical orbits or those within young systems. I have led the discovery and the Rossiter-McLaughlin effect measurements of two significant exoplanets. One of these is TOI-1268b, which is among the youngest known Warm Saturns. The other is TOI-1859b, a clear example of an eccentric and misaligned Warm giant planet and one of the first of its kind to be identified, in favor of planet-planet interaction origin.
  • Boundary Layer Circumplanetary Accretion Dong, Jiang, & Armitage 2021, ApJ, 921, 54 Gas giants are expected to accrete most of their mass via a circumplanetary disk. If the planet is unmagnetized and initially slowly rotating, it will accrete gas via a radially narrow boundary layer and rapidly spin up. Radial broadening of the boundary layer as the planet spins up reduces the specific angular momentum of accreted gas, allowing the planet to find a terminal rotation rate short of the breakup rate. In this work, we quantified the terminal rotation rate of planets accreting from their circumplanetary disks and identified its dependency on the disk's scale height.
  • Debris Disks in Multiplanet Systems Dong, Dawson, Shannon, & Morrison 2020, ApJ, 889, 47 Resolved debris disk features, such as warps, offsets, edges and gaps, azimuthal asymmetries, radially thickened rings, and scale heights, hold valuable information about the underlying planetary systems. This information includes the predicted planet's mass, semimajor axis, and other orbital parameters. Most existing models assume that a single planet is sculpting the disk feature. However, recent observations of mature planetary systems (for example, by radial velocity surveys or through the Kepler mission) have revealed that many planets are part of multiplanet systems. This raises the question: are our inferences compromised by unseen planets? In our research, we investigated whether and how planet properties inferred from single-planet models might be compromised when multiple planets reside within the system.
  • ASTR 405: Planetary Systems An upper-level course on the formation and evolution of planetary systems. Topics include exoplanet detection and characterization, planet formation, planetary atmospheres and interiors, and the physical interpretation of observational data, with an emphasis on quantitative analysis and research-driven learning. Offered in Fall 2025 and Fall 2026. Course materials

Graduate Students

Undergraduate Students

  • Zixuan (Jay) Yan

Undergraduate Research Projects

Undergrads who are interested in working with me, please check Astronomy Research Application Portal for new opportunities. Application deadlines typically occur in November and April.

Roman Data Challenge (Fall 2026)

Roman Data Challenge is a one semester undergraduate research project where students have the opportunity to work on the RGES-PIT data challenge data set to build a pipeline for microlensing event detection and data modeling.

Team members: Luis Gama, Agastya Gaur, Anuva Ghosalkar, Ben Hall-Skank, Kyle Hoske, Matthew Icho, Andrew Pleiman, Gokul Sriramasubramanian

Team Gaia (Fall 2025)

Team Gaia is a one semester undergraduate research project focused on building a Bayesian inference pipeline to infer planetary companion properties from Gaia RUWE measurements. Codes

Team members: Tanay Agrawal, Johnny Cheng, Grace Houlihan, Naavya Jain, Noori Khurshid, Ashi Poorey, Tanmay Raswant, Zixuan (Jay) Yan

Team Gaia Group Photo