I am an astronomer who studies exoplanets: how to find them, how to weigh them, and how common they are.
I am currently a Plaskett Fellow at the National Research Council of Canada's Herzberg Astronomy and Astrophysics Research Centre (NRC HAA) in Victoria, British Columbia.
In July 2027 I will join the Department of Physics and Astronomy at the University of Victoria as an Assistant Professor.
I completed my PhD at the University of Victoria under the supervision of Christian Marois, and hold a Bachelor's in Physics and a Bachelor's in Computing from Queen's University. My thesis received the 2025 Plaskett Medal.
Research
Most of what we know about exoplanets comes from planets close to their stars. Giant planets at the distances of Jupiter and Saturn are much harder to find. Transits are rare at those distances, radial-velocity surveys need decades of data, and direct imaging only detects the youngest, brightest planets. Astrometry, the precise measurement of how stars move across the sky, is most sensitive to exactly these orbits. Here is a short introduction to how it works.
I develop orbit-modelling methods that jointly analyze Gaia and Hipparcos astrometry, radial velocities, direct imaging, and interferometry, so that each kind of data helps constrain the others. With collaborators I recently published G23H, a calibrated combination of Gaia DR2, Gaia DR3 and Hipparcos for finding companions in data that already exists. We have also released Exopost, a public website for browsing orbit posteriors and detection limits for more than 100,000 stars. Gaia's fourth data release, scheduled for 2 December 2026, will be the first to include the individual position measurements for each star. I am preparing to use it to measure how common giant planets and brown dwarfs are, and how that depends on the properties of their host stars.
I also build instruments. I played a major role in SPIDERS, a high-contrast imaging pathfinder now deployed at the Subaru Telescope, which demonstrates new focal-plane wavefront sensing techniques. That work feeds into the GPI 2.0 upgrade for Gemini North, and into technology for future space telescopes such as NASA's Habitable Worlds Observatory.
I have strong interests in applied computational methods including astrostatistics, differentiable physics, and both high-performance and real-time computing. I advocate for the adoption of the Julia programming language in astronomy, and maintain several popular packages including Octofitter and PairPlots. See my research pages for more.
News
- Dec 2026Gaia Data Release 4 is scheduled for 2 December. It will be the first Gaia release with epoch astrometry for every star.
- 2026I have accepted a position as Assistant Professor in Physics and Astronomy at the University of Victoria, starting July 2027. Information for prospective students.
- 2026The G23H catalog paper is published in the Astronomical Journal (Thompson et al. 2026, AJ 172, 53), along with calibrated Gaia DR2 data for 18 million stars.
- 2026Exopost is live: a public browser of companion posteriors and detection limits for more than 100,000 stars.
- 2026Our JWST Cycle 5 program (GO 11023; PI J. Xuan, co-PIs D. Blakely and W. Thompson) will use NIRSpec to search for giant planet candidates identified by astrometry at solar-system-like separations.
- 2025Awarded the Plaskett Medal, given by CASCA and the RASC for the most outstanding Canadian doctoral thesis in astronomy or astrophysics.
- 2025A revised mass and orbit for ε Eridani b: a one-Jupiter-mass planet on a near-circular orbit (Thompson et al. 2025, AJ 170, 301).
- 2024The brown dwarf Gliese 229 B turns out to be a tight binary (Xuan, Mérand, Thompson et al. 2024, Nature).
Contact
Email: William [dot] Thompson [at] nrc-cnrc [dot] gc [dot] ca
Office #332
NRC Herzberg Astronomy and Astrophysics
5071 W Saanich Rd
Victoria, BC V9E 2E7
From July 2027: Department of Physics and Astronomy, University of Victoria.
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Last updated October 2026
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