I am a Senior Lecturer at the University of Southern Queensland. I search for planets around stars outside of our Solar System. These planets teach us about how planetary systems are assembled, and how planets themselves evolve over time.
I have held positions of ARC Future Fellow (2024) and ARC DECRA Fellow (2021) at the University of Southern Queensland. Previously, I was a NASA Hubble Fellow (2017) and CfA Fellow (2015) at the Center for Astrophysics | Harvard & Smithsonian. I received my PhD at the Australian National University in 2015.
Research group
Current students
Sydney Vach | Graduate student | Young planet demographics
Ava Morrissey | Graduate student | Atmospheric escape in young planets
Allyson Bieryla | Graduate student | Obliquities of warm Jupiters
Co-supervision
Emma Nabbie | Graduate student | Exoplanet dynamics
Nataliea Lowson | Graduate student | Exoplanet atmospheres
Tyler Fairnington | Undergraduate student | TESS planet discoveries
Caitlin Auger | Undergraduate student | HST Lyman alpha transits
Past Students
Dr Alexis Heitzmann | Graduate student | Now Geneva Observatory
Chris Wirth | Undergraduate research scholar | Now graduate student at the University of Chicago
Harvard Science Research Mentoring Program | Year long research mentorship for groups of high school students (2018-2020) | Work featured in the Harvard Gazette
Research topics
Young planet demographics
Multiple formation channels may have led to the current Kepler planet distribution. For example, small planets may have formed gas rich, or water rich. It’s difficult to tell them apart by looking at mature planets. Yet they differ significantly in their youth.
Sydney Vach et al. performed an independent census of young planets from TESS with ages less than 200 Myr. In this paper, we computed occurrence rates, and compared the population against planet evolution models.
We found the occurrence rates of super Neptunes (4-8 Earth Radii) to be far more common at these ages compared to mature planets in the Kepler distribution.
Also, there appears to be an excess of planets at the ~10-day orbital period compared to the mature planet sample.
Most importantly, we think this inflated small planet population is most consistent with the idea that small close-in planets are formed gas rich (instead of water rich). These planets contract rapidly as they lose their internal heat from formation. They also evaporate rapidly within this timeframe, scuplting the mature period distribution as they age.
HST program
We have ongoing HST STIS programs to characterise the Lyman-alpha transits for a number of super-Earths and Neptunes around young stars. We hope that by characterising the escaping hydrogen outflow from these planets, we can understand the photoevaporation process that all close-in small planets are expected to undergo.
Doppler tomography
We are measuring the orbital obliquities for a variety of planetary systems. We specialise in the use of Doppler tomography to map the spectroscopic transits of planets about rapidly rotating stars. This is most effective for young and early-type planet hosts.
Recent highlights
A Mini-Neptune from TESS and CHEOPS Around the 120 Myr Old AB Dor Member HIP 94235 – Zhou et al. 2022
Two Young Planetary Systems around Field Stars with Ages between 20 and 320 Myr from TESS – Zhou et al. 2021
Two New HATNet Hot Jupiters around A Stars and the First Glimpse at the Occurrence Rate of Hot Jupiters from TESS – Zhou et al. 2019
The Obliquity of HIP 67522 b: A 17 Myr Old Transiting Hot, Jupiter-sized Planet – Heitzmann, Zhou et al. 2021
A Well-aligned Orbit for the 45 Myr-old Transiting Neptune DS Tuc Ab – Zhou et al. 2020
George Zhou 