Welcome!

My name is Fei Dai (戴飞), and I am a faculty member at the Institute for Astronomy, University of Hawaiʻi. I am currently seeking motivated students and postdocs. Please feel free to reach out for potential collaborations.

Through a combination of novel data analysis techniques and numerical simulations, my group investigates the formation, evolution, and habitability of planetary systems. We are particularly drawn to the most extreme planetary systems such as "ultra-short-period planets", "super-puffs", "resonant chains", and planets on highly misaligned orbits.

Research Highlights

  • Planetary systems locked in chains of mean-motion resonances, likely established through disk-driven migration.

  • Ultra-Short-Period Planets: scorching worlds that complete an orbit in only a few hours.

  • Puzzling low-density planets that defy traditional formation models.

  • Exotic planets on polar or even retrograde orbits around their host stars.

  • Photometric signatures from starspots in transit light curves provide powerful diagnostics of planetary orbital orientation and stellar magnetic activity.

  • Extending the study radius gap (Fulton et al 2018) from Sun-like stars to M-dwarfs. Photoevaporation, rather than core-powered mass loss, seems to be the primary driver for the radius gap.

  • Cutting-edge 3D simulations to explore how hydrodynamic escape erodes planetary atmospheres.

  • K2, the second phase of the NASA Kepler mission, opened the door to discovering many remarkable planetary systems along the ecliptic.

  • A pair of young stars that likely experienced a close encounter recently, as evidenced by optical dimming, tidal arms, and strong Fe X-ray emission.

    • Image credits: NASA/JPL-Caltech/T. Pyle, ESO/L. Calcada, Kley & Nelson, AAS Nova, Addison, Sanchis-Ojeda, Fulton, Haworth.

Publications

  • 182 All Publications
  • 16 First-Authored
  • 6161 Citations
  • 50 h-index
  • 133 i10-index

More up-to-date publication lists can be found here:

Group

Postdocs:

Huan-Yu Teng: Visiting Postdoctoral Fellow, NAOJ/KASI/NAOC

Teng, Dai et al. 2025, ApJ: Stellar Obliquity of the Ultra-short-period Planet System HD 93963

Teng, Dai et al. 2024, AJ: The ~50 Myr Old TOI-942c is Likely on an Aligned, Coplanar Orbit and Losing Mass

Graduate Students:

Rena Lee: Graduate Student, NSF GRFP Fellow, University of Hawaii

Lee, Dai et al. 2025, ApJL: TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf

Elina Zhang: Graduate Student, University of Hawaii

Zhang, Teng, Dai et al. 2025, ApJ: TOI-880 is an Aligned, Coplanar, Multi-planet System

Chase Urasaki: Graduate Student, University of Hawaii

Mu-Tian Wang: Visiting Graduate Student, Nanjing University

Wang, Dai, Liu et al. submitted: An Adolescent, Near-Resonant Planetary System Near the End of Photoevaporation

Wang, Dai et al. submitted: TOI-4495: A Pair of Aligned, Near-Resonant Sub-Neptunes that Experienced Overstable Migration

Zhecheng Hu: Visiting Graduate Student, Tsinghua University

Hu, Dai, Zhu et al. submitted: Unexpected Near-Resonant and Metastable States of Young Multi-Planet Systems

Aaron Householder: Visiting Graduate Student, NSF GRFP Fellow, Massachusetts Institute of Technology, co-advised with Aurora Kesseli

Householder, Dai, Kesseli et al. in prep: The KPF SURFS-UP Survey I: Transmission Spectroscopy of WASP-76 b

Undergraduate Students:

Finnegan Keller: Visiting Undergraduate Student, Brown University; Finnegan's thesis (same title as the paper) won Brown's Smiley Prize for Excellent Contribution to the Astronomy Program. He was also the student speaker at Brown's 2025 Commencement.

Keller, Dai & Xu et al. AJ, in press: Higher-Order Mean-Motion Resonances Can Form in Type-I Disk Migration

Diya Kumar: Visiting Undergraduate Student, SURF, Caltech

Kumar, Dai, et al. in prep: Dynamical Disruption of Resonant Chains

Quentin Charles: REU Undergraduate Student, University of Hawaii

Charles, Dai, et al. in prep: Formation of Hot Jupiters During Type-I Migration

Barron Nguyen: Visiting Undergraduate Student, Standford University, co-advised with Prof. Laura Schaefer

Nguyen, Schaefer, Dai, et al. in prep: A Tidally-Enhanced Outgassed Secondary Atmosphere on 55 Cancri e

Yuancheng Xu: Visiting Undergraduate Student, Oxford University

Xu & Dai, ApJ, 2025: Amplifying Resonant Repulsion with Inflated Young Planets, Overlooked Inner Planets, and Nonzero Initial Delta

Former Students:

Aida Behmard: Caltech Graduate Student co-advised with Andrew Howard, now Kalbfleisch Fellow at American Museum of Natural History

Behmard, Dai, et al., MNRAS, 2023: Planet engulfment detections are rare according to observations and stellar modelling

Behmard, Dai & Howard, AJ, 2022: Stellar Companions to TESS Objects of Interest: A Test of Planet-Companion Alignment

Ryan Rubenzahl: Caltech Graduate Student co-advised with Andrew Howard, now Flatiron Fellow

Rubenzahl, Dai, Howard, et al., ApJ, 2024: Obliquity Constraints for the Extremely Eccentric Sub-Saturn Kepler-1656 b

Rubenzahl, Dai, Howard, et al., AJ, 2024: KPF Confirms a Polar Orbit for KELT-18 b

Rubenzahl, Dai, Howard, et al., AJ, 2024: The TESS-Keck Survey. XII. A Dense 1.8 R ⊕ Ultra-short-period Planet Possibly Clinging to a High-mean-molecular-weight Atmosphere after the First Gigayear

Rubenzahl, Dai, Howard, et al., AJ, 2021: TESS-Keck Survey. IV. A Retrograde, Polar Orbit for the Ultra-low-density, Hot Super-Neptune WASP-107b

Sarah Lange: Caltech WAVE Student co-advised with Andrew Howard

Community Service and Outreach

  • A free online workshop designed for undergraduates who aspire to become astronomers.

  • Check out some public talks I gave recently.

  • I mentored students in the Caltech WAVE Program, which empowers undergraduates from underrepresented groups to pursue research in STEM.

Brief Bio

Previously, I was a NASA Sagan fellow at Caltech where I worked with Prof. Andrew Howard and Prof. Heather Knutson. I received my PhD in Physics from MIT in 2019 under the supervision of Prof. Josh Winn in 2019. I earned my undergraduate degree from the University of Cambridge in 2014.