Canadian Astronomical Society
2025 J.S. Plaskett Medal: William Thompson
CASCA is pleased to announce Dr. William Thompson as the 2025 recipient of the Plaskett Medal for the most outstanding doctoral thesis in astronomy or astrophysics.
Dr. Thompson’s thesis, defended at the University of Victoria in 2023 under the direction of Profs. Falk Herwig and Christian Marois, is entitled, “Lights in Motion: Observing Nearby Planets with Imaging, Wavefront Sensing, Orbital Detection, and Spectroscopy”. The title hints at the breadth of the research described within Dr. Thompson’s thesis work, including developing new computational methods to analyze angular differential imaging observations and employing these methods to discover a new candidate exoplanet around HR 8799; developing the first multi-technique exoplanet finding code that can incorporate radial velocity, astrometry and high-contrast imaging data; carrying out both simulation and laboratory tests of two new techniques for exoplanet imaging; and more. The thesis external examiner notes that, “it is the combination of innovative thinking, rigorous simulation and laboratory testbed results which make the work so impressive.” The software developed as part of Dr. Thompson’s thesis research is publicly available and is already being used by other exoplanet researchers, and his instrumentation development work provides first steps toward possible hardware contributions to the Habitable Worlds Observatory. CASCA is delighted to recognize Dr. Thompson for these outstanding contributions.
Dr. Navarro obtained his PhD from Universidad Nacional de Córdoba, in Argentina, and is currently a Professor in the Department of Physics and Astronomy at the University of Victoria. As one of the leading cosmologists in Canada and the world, he has made many lasting impactful contributions to the field of computational cosmology, including landmark work on the intrinsic structure of dark matter halos. His work has proved essential to our understanding of the role of dark matter in the large-scale structure of the universe and in galaxy formation and evolution. Dr. Navarro’s contributions also include studies of dissipative effects on satellite galaxies, the collapse and shock-heating of non-radiative gas during the formation of galaxy clusters, and the formation and evolution of galactic disks. He was a pioneer of the “smoothed-particle hydrodynamics” (SPH) simulation technique, which remains the dominant tool allowing scientists to understand galaxy formation and evolution. Dr. Navarro has mentored numerous graduate students and postdoctoral researchers who have gone on to highly successful scientific careers.
CASCA is delighted to recognize Dr. Navarro’s efforts with this award.
2024 J.S. Plaskett Medal: Antoine Bédard
Dr. Bédard received his PhD from Université de Montréal, under the supervision of Drs. Pierre Bergeron and Pierre Brassard, and is now a postdoctoral researcher at the University of Warwick (UK). His thesis, titled ‘Characterization and modeling of the spectral evolution of hot white dwarf stars’, combines observations, model atmosphere and stellar evolution calculations, data analyses, and interpretations. Dr. Bédard’s thesis begins with spectroscopic analysis of 2000 hot white dwarfs, providing our best picture of white dwarf spectral evolution. He then substantially reworked the STELUM stellar evolutionary code and used this to simulate white dwarf spectral evolution. Finally, he applied his numerical simulations to self-consistently explain the physics behind the spectral evolution of white dwarfs as they cool, solving several well-known longstanding problems in the study of white dwarfs. Dr. Bédard’s thesis introduction provides a thorough overview of the study of white dwarfs for graduate students and other researchers working on this topic, and his papers have already had a wide impact in the field.
2023 J.S. Plaskett Medal:
Deborah Lokhorst
Dr. Lokhorst received her PhD in 2022 under the supervision of Dr. Roberto Abraham at the University of Toronto, and she is now a Herzberg Instrument Science Fellow at NRC Herzberg Astronomy & Astrophysics Research Centre. Her thesis titled “Ultra-Narrowband Imaging with the Dragonfly Telephoto Array: Toward the Cosmic Web” is a tour-de-force combining theory, observation, and instrumentation. Dr. Lokhorst played a central role in the construction and scientific exploitation of the Dragonfly Telephoto Array, opening a new window on the ‘low surface brightness Universe’. Her thesis work began with an analysis of hydrodynamical simulations to understand the observational limits needed to directly detect ‘invisible’ gas in the circumgalactic medium (CGM) around nearby galaxies. She then designed, machined, and assembled the prototype of a new component of the Dragonfly Telephoto Array, the ‘Filter-Tilter’, to allow the required limits to be achieved. She finally obtained the first scientific observations taken by a pathfinder Dragonfly narrowband imager, discovering a giant ionized gas cloud in the CGM of the starburst galaxy M82.
2022 J.S. Plaskett Medal:
Deborah Good
Dr. Good received her PhD in 2021 under the supervision of Dr. Ingrid Stairs at UBC, and she is now a postdoctoral fellow at the University of Connecticut and the Flatiron Center for Computational Astrophysics. Her thesis, “Timing Pulsars and Detecting Radio Transients with CHIME,” includes groundbreaking work on the first few months of pulsar and fast radio burst detections with CHIME. To complete this research, she led efforts within the CHIME team to calibrate instruments, write software, verify events, and is on the cutting edge of trying to discover whether or not all Fast Radio Bursts are repeating events. She also collected pulsar data, discovered many new pulsars, and adapted the NANOGrav pipeline to work for CHIME data, laying the groundwork for data processing that will be needed in the next couple of years.
2021 J.S. Plaskett Medal:
Ziggy Pleunis
Dr. Pleunis completed his PhD thesis in 2020 under the supervision of Prof. Victoria Kaspi at McGill University, and will soon be moving to the University of Toronto as a Dunlap Fellow. His thesis, titled “Fast radio burst detection and morphology with the CHIME telescope” represents a set of groundbreaking contributions to the fast-emerging field of Fast Radio Burst (FRB) astronomy. Dr. Pleunis has contributed to all aspects of the CHIME telescope’s FRB project, from instrumentation to software to observation to analysis to science interpretation. Beyond CHIME, he has also made multiple breakthroughs using the LOw Frequency Array (LOFAR), whether in the discovery of a low-frequency FRB or the study of millisecond pulsars.
2020 J.S. Plaskett Medal:
Simon Blouin
Dr. Blouin received his PhD thesis in 2019 under the supervision of Prof. Patrick Dufour, and is currently a Director’s Postdoctoral Fellow at Los Alamos National Laboratory. His thesis, titled “Modeling of high-density effects at the photosphere of cool white dwarf stars”, resolves a longstanding problem in the theory of white dwarf atmospheres, which could not reproduce the emergent flux from cool helium-rich white dwarfs, casting doubt on the foundations of the theory and reliability of its predictions, with implications for the study of galactic stellar populations using white dwarf dating. Dr. Blouin re-worked these atmospheric calculations from first principles, using a variety of techniques, extending the validity of atmospheric models and successfully accounting for cool white dwarf observations, thereby filling a crucial need in the community.
2019 J.S. Plaskett Medal:
Alexandra Tetarenko
Dr. Tetarenko’s doctoral thesis is on the physics of relativistic jets in X-ray binaries, as revealed by radio, millimeter (mm), and sub-millimeter (sub-mm) observations. Dr. Tetarenko published six papers as a first author as part of her thesis, and was the second author on a recently accepted Nature paper. Dr. Tetarenko demonstrates exceptional skills both as an observer and in the physical interpretation of complex observational data, and has become a leading expert in mm/submm observations of black hole X-ray binaries. Currently a 2018 East Asian Observatory Fellow, Dr. Tetarenko continues to excel, recently publishing an investigation into Radio Frequency Timing Analysis of the Compact Jet in the Black Hole X-ray Binary Cygnus X-1.
2018 J.S. Plaskett Medal: Gwendoline Eadie
Dr. Eadie completed her doctoral studies at McMaster University under the supervision of Dr. William Harris. In her thesis entitled “Lights in Dark Places: Inferring the Milky Way Mass Profile using Galactic Satellites and Hierarchical Bayes”, she developed a high-level statistical method to derive the mass and mass distribution within astrophysical systems. Mass is a fundamental variable driving the evolution of galaxies like our Milky Way, but it is notoriously difficult to measure due to the fact that it is dominated by the dark matter extending well beyond the visible starlight. This challenge is compounded by incomplete data on the positions and velocities of “tracer particles” such as stars, star clusters and dwarf satellites scattered through the galaxy’s halo. Dr. Eadie developed a powerful Bayesian formulation of the problem combined with Markov Chain Monte Carlo calculations of the relevant parameters in the problem and their probability distributions. Her formulation also included a hierarchical treatment of measurement uncertainties for each tracer. She used it to place a new constraint on the mass profile and total mass of the Milky Way, and it will be a very powerful tool in the exploitation of future very large datasets from the Gaia mission and the Large Synoptic Survey Telescope (LSST).
2017 J. S. Plaskett Medal: Fereshteh Rajabi
Dr. Rajabi completed her doctoral studies at the University of Western Ontario under the supervision of Dr. Martin Houde. Her thesis entitled “Dicke’s Superradiance in Astrophysics” extends the mathematical description of this intriguing physical process to many phenomena of astrophysical interest. Superradiance is a quantum mechanical and coherent behaviour between closely spaced atoms or molecules (i.e., several within a wavelength) that makes them, when certain conditions are met, emit radiation that is much more focused and intense than expected. Dr. Rajabi used superradiance to elegantly explain anomalous fluxes in the 21cm line of hydrogen atom and unexplained maser flares and bursts in the envelopes of evolved stars. She made fundamental physical advances that brought superradiance out of the lab and into an ever more surprising Universe. Her work has attracted worldwide attention not only in astrophysics, but also in the field of quantum optics.
2016 J.S. Plaskett Medal: Jonathan Gagné
Dr. Gagné completed his doctoral studies at l’Université de Montréal under the supervision of Dr. David Lafrenière and Dr. René Doyon. His thesis, entitled “La recherche de naines brunes et étoiles de faible masse dans les associations cinématiques jeunes du voisinage solaire”, identifies and characterizes new substellar mass objects that belong to nearby young associations of stars. Dr. Gagné developed a powerful new algorithm to select highly probable substellar objects in young associations that is now widely used by the community. He also carried out an all-sky survey to identify, follow-up and characterize actual candidates, more than doubling the number of confirmed brown dwarfs.
Dr. Gagné is now widely recognized as a leading figure in the study of nearby young substellar objects.
Dr. Gagné is currently a Sagan Postdoctoral Fellow in the Department of Terrestrial Magnetism at the Carnegie Institution for Science, where he will work to identify and characterize young brown dwarfs with only a few times the mass of Jupiter.
2015 J. S. Plaskett Medal: Anne Archibald
Dr. Archibald completed her doctoral studies at McGill University in 2013 under the supervision of Dr. Vicki Kaspi. Her thesis, entitled “The End of Accretion: The X-ray Binary/Millisecond Pulsar Transition Object PSR J1023+0038”, reports the discovery and detailed study of an eclipsing binary radio pulsar. Using several different telescopes at a variety of wavelengths, Dr. Archibald established the transitional nature of the system from low-mass X-ray binary to millisecond radio pulsar, the first such object discovered and a key “missing link” in our understanding of neutron star binary evolution.
2014 J. S. Plaskett Medal: Andrew Pon
Dr. Pon completed his doctoral studies at the University of Victoria in 2013 under the supervision of Dr. Douglas Johnstone (UVic, NRC-Herzberg). His thesis, entitled “Shocks, Superbubbles, and Filaments: Investigations into Large Scale Gas Motions in Giant Molecular Clouds”, covers a wide range of topics in star formation — including gravitational collapse, turbulent heating, and Galactic ecology. This work bridges theory and observations, and crosses traditional boundaries between the detailed investigation of individual nearby star-forming regions and the much larger scale studies of galactic-scale star formation.
2013 J. S. Plaskett Medal: Yasuhiro Hasegawa
Dr. Hasegawa completed his doctoral studies in 2012 at McMaster University. His thesis, entitled “Planet Traps in Protoplanetary Disk and the Formation and Evolution of Planetary Systems”, was carried out under the supervision of Prof. Ralph Pudritz. This work explores in detail — from both a theoretical and computational perspective — the possibility that inhomogeneous structure in protostellar accretion disks can create ‘planet traps’ where major planets are built up primarily through the capture of rapidly migrating planetary cores, followed by the accretion of dense gas.