CITA extends a warm welcome to our incoming Fellows and National Fellows. This Fall we are joined by an unprecedented number of talented Postdoctoral and National Fellows. We are committed to providing post-doctoral training for early career researchers in the field of Theoretical Astrophysics and are excited about the contributions these outstanding researchers will bring to CITA.

Weikai Cui

Dr. Weikai Cui joined CITA as a Postdoctoral Fellow in October 2026 after earning his doctorate from the University of Virginia in 2026. His research focuses on astrochemistry, interstellar molecules, chemical processes in the interstellar medium, and reactions occurring on icy grain surfaces. His work combines theoretical and computational chemistry with astrophysical applications to understand the molecular evolution of interstellar environments and the chemical processes that precede star and planet formation.

Paul Huet

Dr. Paul Huet is joining CITA as a Postdoctoral Fellow in November 2026, after earning his doctoral degree at the Paris Observatory. His research focuses on planetary formation, planetary atmospheres, protoplanetary and debris disks, gas accretion onto planets, numerical modeling and observations, and exoplanets. His work combines numerical modeling with observations to investigate the formation and evolution of planetary systems, including the interaction between planets and their surrounding gaseous and dusty environments.

Sóley Hyman

Dr. Sóley Hyman is a CITA National Fellow at Queen’s University. She earned her Ph.D. from the University of Arizona in 2026. Her research focuses on galaxy dynamics, stellar orbits, chaos, and computational methods, with particular interest in the internal dynamics of galaxies. She studies how evolving stellar orbits drive morphological changes in galaxy simulations, including the role of chaotic stellar orbits in the evolution of bars and boxy-peanut-X (BPX) structures in disk galaxies.

Christian Kragh Jespersen

Dr. Christian Kragh Jespersen is a CITA National Fellow and Schmidt AI in Science Fellow. His research focuses on galaxy evolution, astrostatistics, machine learning, and spectroscopy. He develops statistical and machine-learning methods for studying how galaxies and dark-matter halos form and cluster, with research spanning JWST observations of early galaxies to the study of Earth’s own night-sky glow. His work combines astronomical observations with statistical and computational methods to extract physical information from large datasets.

Xuan Ji

Dr. Xuan Ji joined CITA as a Postdoctoral Fellow in October 2026, after receiving her Ph.D. in Geophysical Sciences from the University of Chicago in 2026. Her research focuses on rocky exoplanet atmospheres, climate, and habitability. She uses both low-order mathematical models and numerical simulations to study the coupled dynamics of small rocky exoplanets’ interiors, atmospheres, and orbits. At CITA, she will contribute to an international effort to develop next-generation computational frameworks that connect physics-based models of exoplanet interiors and atmospheres with limited observations.

Ilija Medan

Dr. Ilija Medan joined CITA as a Postdoctoral Fellow in July 2026. He earned his Ph.D. from Georgia State University in 2023 under the supervision of Dr. Sébastien Lépine and subsequently served as a VIDA Postdoctoral Fellow at Vanderbilt University from 2023 to 2026 under the supervision of Dr. Keivan Stassun. His research focuses on low-mass stars, the Solar Neighborhood and stellar populations, binary stars, spectroscopic surveys, astroinformatics and astrostatistics, and Milky Way chemodynamics. At CITA, he works under the advisement of Dr. Juna Kollmeier and contributes to SDSS-V, where he serves as FPS Design Implementation Lead, Solar Neighborhood Working Group Co-Chair, and a member of the Milky Way Mapper Data Analysis team.

William McClymont

Dr. William McClymont joined CITA as a Postdoctoral Fellow in September 2026 after completing his Ph.D. at the Kavli Institute for Cosmology, University of Cambridge. His research focuses on galaxy evolution, high-redshift galaxies, star clusters, supermassive black holes, radiation-hydrodynamic simulations, and Monte Carlo radiative transfer. He combines cosmological radiation-hydrodynamic simulations with observations to investigate why galaxies formed and grew so rapidly in the early Universe and how this relates to the formation of dense star clusters, including the progenitors of globular clusters.

Maja Lujan Niemeyer

Dr. Maja Lujan Niemeyer is an incoming CITA National Fellow at the University of British Columbia, where she will work with the CHIME group. She recently completed her Ph.D. in Physics at the Max Planck Institute for Astrophysics and Ludwig-Maximilians-Universität München, under the supervision of Professor Eiichiro Komatsu. Her research focuses on line-intensity mapping, large-scale structure, and the Lyman-α emission line, using observations of diffuse emission to study galaxies, intergalactic gas, and the evolution of the early Universe. She is a member of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) collaboration. Her recent work includes the first detection of the galaxy–Lyman-α intensity cross-power spectrum in HETDEX data, providing a precise measurement of line-intensity mapping at cosmological scales.

Catherine Psarakis

Dr. Catherine Psarakis joined CITA as a Postdoctoral Fellow in October 2026 after completing her Ph.D. in the Department of Earth, Planetary, and Space Sciences at UCLA. Her research focuses on magnetic induction, icy moons, interior modeling, planetary habitability, astrobiology, alternative solvents, and planetary geochemistry. She combines planetary-interior and magnetic-induction modeling with laboratory experiments investigating ionic liquids and deep eutectic solvents under planetary conditions. Her work includes research conducted at NASA’s Jet Propulsion Laboratory and seeks to connect planetary geophysics, geochemistry, and astrobiology in understanding where persistent liquid environments may exist within Solar System bodies and exoplanets. She is also an AAUS Scientific Diver, with interests in terrestrial analogue environments for planetary science and astrobiology.

Soumendra Kishore Roy

Dr. Soumendra Kishore Roy is a Canada Impact+ Postdoctoral Fellow and a CITA Postdoctoral Fellow, who joined CITA in July 2026. He earned his Ph.D. from Stony Brook University in 2026. His research focuses on massive stellar evolution, gravitational-wave astrophysics, and gravitational-wave cosmology, with particular interest in population and cosmological-parameter inference. His core expertise is in hierarchical Bayesian inference, which he uses to connect models of binary stellar evolution with observations of compact-binary mergers and investigate their origins. He is involved in research associated with the LIGO–Virgo–KAGRA (LVK) Collaboration.

Sabina Sagynbayeva

Dr. Sabina Sagynbayeva is a CITA National Fellow whose research spans exoplanets, stars, astrostatistics, numerical simulations, theoretical astrophysics, and data analysis. Originally from Kazakhstan, she earned her Ph.D. from Stony Brook University. Her scientific interests include planet formation, the orbital architecture of exoplanets, and stellar magnetic activity. She also maintains an interdisciplinary creative practice in acting and singing.

Hui Tong

Dr. Hui Tong is joining CITA as a Postdoctoral Fellow after receiving his doctorate from Monash University in 2026. His research focuses on gravitational-wave astronomy, compact-object mergers, black-hole populations, and Bayesian inference. His work uses gravitational-wave observations to investigate the properties and origins of merging compact objects and the astrophysical populations that produce them. He is affiliated with the LIGO–Virgo–KAGRA (LVK) Collaboration and the OzGrav ARC Centre of Excellence for Gravitational-Wave Discovery.

Jonathan Zhang

Dr. Jonathan Zhang begins his Postdoctoral Fellowship at CITA after completing his doctorate at the University of Toronto in 2026. His research focuses on fast radio bursts and high-energy astrophysical phenomena, with particular interest in the physical mechanisms that generate these short-duration radio transients and their possible connections to magnetars and extreme magnetic environments.

Saiyang Zhang

Dr. Saiyang Zhang joins CITA as a Postdoctoral Fellow after completing his Ph.D. in Physics at the University of Texas at Austin in August 2026. His research focuses on dark matter, the early Universe, primordial black holes, Population III stars, supermassive black holes, and large-scale structure, combining theoretical modelling, cosmological simulations, and computational methods to investigate the evolution of cosmic structure. His recent work has examined how primordial black holes may influence the formation of the first stars and galaxies and potentially seed the supermassive black holes observed in the early Universe, including through observations with JWST. He is also increasingly interested in machine learning and scientific discovery, including simulation-based inference and the application of large language models to cosmology and dark-matter research.

September 14, 2026

By Lyuba Encheva, CITA

When Anupam Mazumdar first arrived in Canada in 2002, he was a CITA National Fellow stationed at McGill University, working at the frontier where particle physics meets the early universe. More than two decades later, he is returning to the Canadian Institute for Theoretical Astrophysics (CITA) at the University of Toronto as a full professor. In the intervening years, Prof. Mazumdar has developed one of the most distinctive research programs in theoretical physics: an attempt to catch gravity itself behaving like a quantum object, not out in space, but on a tabletop.

From the early universe to the quantum nature of spacetime

Mazumdar’s career has taken him through a remarkable circuit of the world’s leading theoretical physics institutes — Imperial College London, the International Centre for Theoretical Physics in Trieste, McGill, NORDITA and Niels Bohr Institute in Copenhagen, Lancaster University, and most recently the Van Swinderen Institute at the University of Groningen. Along the way, he built a reputation across several distinct areas of theoretical physics. These include cosmic inflation and the physics of the very early universe’s phase transitions. Prof. Mazumdar is also known for his “infinite derivative” theories of gravity — modified versions of general relativity designed to avoid the singularities — such as those at the centres of black holes — that plague Einstein’s original theory.

But it is a more recent line of work that has come to define his research identity. In 2017, Mazumdar and collaborators proposed an experimental protocol to test, in a laboratory, whether gravity is fundamentally quantum in nature. The idea, known as the Quantum Gravity Induced Entanglement of Masses (QGEM) protocol, asks a deceptively simple question: if you place two small masses side by side in quantum superpositions and let them interact only through their mutual gravitational pull, will gravity be able to entangle them the way quantum particles routinely entangle through electromagnetic or other known Standard Model forces? If it can, that would be direct evidence that gravity carries information the way quantum fields do — a long-sought clue in the decades-long effort to reconcile general relativity with quantum mechanics.

It is an audacious idea precisely because gravity is so weak. Unlike collider physics, which pushes to ever-higher energies to probe fundamental interactions, Mazumdar’s approach pushes toward ever more delicate, ever more isolated quantum systems — nanocrystals cooled and levitated with enough precision that gravity’s faint pull between them might, just barely, leave a detectable quantum fingerprint. In 2022, he extended the idea further, proposing a quantum-optics analog of the classic light-bending test of general relativity. This time the intention was to test whether the exchange of a single graviton could entangle photons and matter in quantum superposition.

The envisioned hardware for the flagship QGEM experiment is as exotic as the physics it is meant to probe: nanodiamonds (10 picogram mass), embedded with nitrogen-vacancy centres — atomic-scale defects that act as controllable quantum spins — levitated above a current-carrying superconducting chip and cooled toward the quantum regime in both their internal and centre-of-mass motion. A Stern-Gerlach-type protocol would use the embedded spin to split each nanodiamond into a spatial superposition, hold it open for roughly a tenth of a second to a full second, and then look for the telltale entangling phase that only a genuinely quantum gravitational interaction could imprint. The central experimental headache is separating that faint gravitational signal from electromagnetic backgrounds, since electromagnetic effects can be shielded away but gravity cannot — turning the experiment into what amounts to a very carefully controlled game of hide-and-seek with nature.

This is not a solo effort. Prof. Mazumdar is a co-principal investigator of the MAST-QG collaboration, which brings together University College London, Yale, Northwestern, and Warwick, and the QGEM program has drawn support from major philanthropic science funders, including the Gordon and Betty Moore Foundation and the Alfred P. Sloan Foundation. It is, in other words, an internationally resourced, multi-institution bet on a genuinely novel way of probing fundamental physics — and one that a research group at CITA now has a direct stake in.

Why CITA

CITA has long been a home for physicists who treat gravity and cosmology as an integrated whole — the origin of cosmic structure, the physics of the very early universe, gravitational waves, black holes and compact objects. Mazumdar’s work extends that tradition into a domain the Institute has not historically had in-house: table-top, laboratory tests of gravity’s quantum character. Rather than looking to the cosmos for evidence of quantum gravity’s effects, he is trying to manufacture the conditions for it in a lab on Earth — an approach that is complementary to, rather than in competition with, CITA’s traditional strengths in astrophysical gravity and cosmology.

There is also a symmetry to the appointment that is hard to overlook. Mazumdar’s first taste of Canadian science came as a CITA Fellow at McGill more than twenty years ago, at a formative stage in his career when he was still establishing himself in cosmology and particle physics. His return to CITA itself, now as a senior faculty member leading an internationally recognized experimental-theory program, closes a loop that began at the very outset of his career — and brings with it not just his own research group, but an entry point for CITA into the fast-moving, interdisciplinary field of quantum information science as it intersects with gravity.

With roughly 240 published papers, three major review articles in journals including Physics Reports and Reports on Progress in Physics, a multi-institution collaboration in MAST-QG, and philanthropic funding already secured from the Moore and Sloan foundations, Mazumdar arrives at CITA with both a substantial body of foundational work behind him and an ongoing, high-profile experimental program still very much in motion. For an institute built on the premise that some of the deepest questions in physics — the origin and fate of the universe, the nature of black holes, the unification of gravity and quantum mechanics — require sustained, focused theoretical effort, his presence adds a genuinely new avenue toward one of the oldest open problems in physics: whether gravity, like everything else we know, is quantum after all.

September 11, 2026

New simulations show that a white dwarf torn apart by an intermediate-mass black hole can detonate into a thermonuclear supernova. This explosion resembles those from double-white-dwarf mergers, but its brightness and spectra vary dramatically depending on viewing angle.

The study, recently published in Astronomy & Astrophysics, was led by CITA Postdoctoral Fellow and from the Institut d’Astrophysique de Paris, as well as co-authored by Taeho Ryu and Rüdiger Pakmor. The team combined high-resolution hydrodynamic simulations with detailed radiative-transfer modelling to predict, for the first time at this level of detail, what these rare events would actually look like from Earth.

A white dwarf’s close call

Intermediate-mass black holes — weighing in at somewhere between 100 and 100,000 times the mass of the Sun — are thought to lurk in the dense cores of some star clusters, but they are notoriously difficult to detect directly. One promising way to find them is to catch them in the act of tidally disrupting a passing star. Because white dwarfs are so dense, they can only be torn apart by black holes in this intermediate mass range; if a white dwarf strays too close to a much larger supermassive black hole, it disappears without a trace.

Using the moving-mesh hydrodynamics code AREPO, equipped with a 55-isotope nuclear reaction network, the team modeled the disruption of a compact carbon-oxygen white dwarf by a black hole roughly 500 times the Sun’s mass, varying how close the encounter was. This was followed by radiative-transfer calculations using the codes CMFGEN and LONG_POL to understand the observations of such events. Their key findings:

• A vast array of outcomes: The closest encounters compress the white dwarf so violently that runaway nuclear fusion ignites, converting anywhere from about 1% to as much as 82% of the star’s material into radioactive nickel-56 — the same isotope that powers ordinary Type Ia supernovae — depending on exactly how close the pass was. More distant encounters simply disrupt the star without triggering an explosion.
• A spectrally-diverse, lopsided explosion: ��The disrupted debris has an onion-shell-layered structure of isotopes and fans out towards one direction, material spreading across an extremely wide range of velocities.
• It depends where you’re standing: Radiative-transfer modeling of the resulting light shows rise times and peak brightness comparable to normal Type Ia supernovae — but with an unusually strong dependence on viewing angle, meaning the same explosion could look very different to observers positioned in different directions. Models of spectra reveal a diverse range of potentially observable spectral lines depending on the extent of nuclear burning in the disrupted white dwarf. Months later, characteristic emission lines in the fading afterglow can appear shifted and distorted by thousands of kilometers per second, offering a potential telltale signature of these events.

Why it matters

Because white dwarfs cannot survive close encounters with far larger supermassive black holes, catching one of these disruption events in progress would be strong, direct evidence for the presence of an elusive intermediate-mass black hole — the missing link between stellar-mass and supermassive black holes. With next-generation surveys such as the Vera C. Rubin Observatory expected to discover far more tidal disruption events than ever before, the distinctive light curves, spectra, and viewing-angle dependence identified in this study could help astronomers pick out these rare white dwarf disruptions from the broader population of transients — and, in the process, help pin down where intermediate-mass black holes are hiding.

Publication details

Pavan Vynatheya, Luc Dessart, Taeho Ryu, and Rüdiger Pakmor, “Asymmetrical thermonuclear supernovae triggered by the tidal disruption of white dwarfs,” accepted for publication in Astronomy & Astrophysics, 2026.��

Media Contact:
Lyuba Encheva, Communications and Events Coordinator
Canadian Institute for Theoretical Astrophysics, University of Toronto
Email: communication@cita.utoronto.ca

September 9, 2026

Magnetohydrodynamic modelling shows that colliding and merging stars produce distinct “fingerprints,” offering a new way to trace the violent origins of unusual stars such as blue stragglers.

A study published recently��in��The Astrophysical Journal��provides the most detailed comparison yet of what happens when two stars collide versus when two stars in a binary system merge together — two processes long suspected of producing similar-looking, rejuvenated stars, but which turn out to leave behind different physical signatures.

The research, led by CITA Postdoctoral Fellow along with Taeho Ryu, Chen Wang, Alison Sills, and Rüdiger Pakmor, used the moving-mesh magnetohydrodynamics code AREPO to simulate collisions and mergers of main-sequence stars between five and ten times the mass of the Sun. The team then compared the internal structure, rotation, chemical mixing, and magnetic fields of the resulting objects in detail.

Two roads, two different destinations

Both stellar collisions — sudden, high-speed encounters typically occurring in the crowded cores of dense star clusters — and binary mergers — the slower coalescence of two stars after unstable mass transfer — are known to produce more massive, rapidly rotating stars with hydrogen-enriched cores. These “rejuvenated” stars are prime candidates for explaining blue stragglers, a class of stars that appear anomalously bright and hot for their host clusters, as well as other exotic objects such as magnetic massive stars.

However, it has been difficult to tell these two formation pathways apart. The new simulations identify several distinguishing features:

• Chemical mixing: Merger products retain core hydrogen fractions up to 10% higher than collision products, reflecting differences in how thoroughly the two processes mix stellar material.
• Magnetic field structure: Turbulent mixing dramatically amplifies magnetic fields (by nine to twelve orders of magnitude) in both scenarios, but the character of the resulting fields differs: near-head-on (small-impact-parameter) collisions generate small-scale, tangled magnetic fields likely to fade over time, while mergers and grazing (large-impact-parameter) collisions generate large-scale, ordered fields that may persist far longer.
• Outflows: Only merger products in the study produced magnetically driven, bipolar outflows, with material streaming away at speeds up to 300 kilometers per second — a feature entirely absent from the collision products.

Why it matters

Distinguishing collision products from merger products has been a long-standing challenge for astronomers trying to interpret observations of blue stragglers, magnetic OB stars, and other objects thought to form through stellar interactions. Because collisions dominate in dense globular clusters while mergers are thought to be more common in sparser open clusters, being able to identify a star’s formation history from its magnetic and structural properties could sharpen models of how star clusters evolve and how exotic, highly magnetized stars, and potentially magnetars, come to be.

The authors note that the long-term evolutionary consequences of these differences, particularly whether the ordered magnetic fields in merger products survive over stellar lifetimes, warrant further study.

Publication details

Pavan Vynatheya et al 2026, “The Collision and Merger Products of Stars Do Not Look Alike: A Magnetohydrodynamics Comparison,” The Astrophysical Journal, Volume 999, Number 1. .

Media Contact:
Lyuba Encheva, Communications and Events Coordinator
Canadian Institute for Theoretical Astrophysics, University of Toronto
Email: communication@cita.utoronto.ca

August 27, 2026

By Cynthia Macdonald,

Internationally renowned astrophysicist and planetary scientist Sara Seager will officially join the��Canadian Institute for Theoretical Astrophysics (CITA)��at the University of Toronto on October 1 as North Star Distinguished Professor. This honour accompanies another of significance: she has been named the Eddie Goldenberg Research Chair in Planetary and Molecular Sensing Technologies.

�ճ������program is designed to support institutions in attracting world-leading researchers whose work addresses critical national and global challenges. First announced in last year’s federal budget, the program emphasizes both research excellence and tangible impact.

Seager’s career exemplifies the program’s ambitious mandate. Since the 1990s, she has contributed foundational knowledge to the understanding of exoplanets, or planets that exist outside our solar system. Her research has already led to the discovery of an exoplanet atmosphere, and contributed to the first detection of light emitted from an exoplanet.

She leads the Venus Morning Star Missions, which aim to search for signs of microbial life in Venus’s cloud decks. Seager’s pioneering work draws us closer to the possibility of finding life on another planet.

As Eddie Goldenberg Distinguished Research Chair, Seager will develop miniature molecular sensors capable of detecting trace organic compounds at unprecedented sub-part-per-trillion levels. She will also develop next-generation computer models of planetary and environmental systems, coupled to space mission design.��The program will translate technologies being developed for planetary exploration into applications including environmental monitoring, chemical detection, and Earth remote sensing.

“I am honoured to be part of this exceptional new Canadian program,” says Seager.��“Space exploration pushes us to develop technologies to new limits, and the Eddie Goldenberg Distinguished Research Chair will enable my team to translate new developments into advanced tools here on Earth.”

Seager’s research will be supported through cross-appointments with the Departments of  a�Ի� , as well as the  with funding from the Dunlap Institute for Astronomy & Astrophysics.

“CITA’s mission is to push the frontiers of astrophysics through cutting-edge research,” says Shantanu Basu, interim director of CITA. “Sara Seager’s work is at the forefront of studying exoplanetary systems and atmospheres. She brings to Canada a dynamic, interdisciplinary research program with the potential to transform our search for extraterrestrial life.”

Her appointment at CITA marks a return to her alma mater: before earning her PhD from Harvard in 1999, she graduated as a math and physics specialist from U of T in 1994. In 2023, she received an  for her leadership in the fields of astrophysics and planetary science.

���������, dean of the Faculty of Arts & Science: “It’s my great pleasure to congratulate Sara Seager on being named a 2026 Eddie Goldenberg Distinguished Research Chair. Thanks to Professor Seager’s highly interdisciplinary research, we are learning more every day about the habitability of planets and the search for life across the cosmos. I’m honoured to welcome her back to U of T, where her inspiring career was first conceived.”

Seager joins CITA from the Massachusetts Institute of Technology, where she was professor of physics, professor of planetary science and professor of aeronautics and astronautics. Over the course of her career, she has received many accolades including the Kavli Prize in Astrophysics, a MacArthur Fellowship (or “genius grant”), and the distinction of Officer of the Order of Canada.

August 25, 2026

Are all merging compact objects that produce gravitational waves black holes, or are some of them highly convincing imposters?

A new study published on August 14, 2026 in the prestigious journal Physical Review Letters has brought scientists one step closer to answering this fundamental question. Co-led by Dr. Aditya Vijaykumar, a Postdoctoral Fellow at the Canadian Institute for Theoretical Astrophysics (CITA) at the University of Toronto, the research uses recent gravitational wave data to check for “Exotic Compact Objects” (ECOs)—hypothetical structures that mimic black holes but lack an event horizon from which nothing can escape.

The international research team focused their attention on GW241011, a massive gravitational wave event generated by a violent cosmic collision. The larger of the two colliding bodies (the “primary”) was roughly 20 times the mass of our sun and spinning incredibly fast, making it the perfect laboratory to test the laws of fundamental physics.

To determine if this object was a true black hole or an exotic imposter, the team measured its “spin-induced quadrupole moment.”

“When an object spins rapidly, it bulges at its equator. How much it bulges depends entirely on what it is made of,” explains Dr. Vijaykumar, one of the lead authors of the study. “Because the more massive object in GW241011 was spinning so fast, the gravitational wave data provided us with the tightest constraints ever recorded on this bulging effect. This allowed us to test beyond the standard realm of black holes.”

One of the leading theoretical candidates for black hole imposters is a “Boson star”—a hypothetical compact object that��would be made of a yet-to-be-discovered heavy Boson particle (like the theoretical “Axion”). Because Bosons��can��share the exact same space, they don’t push back the way neutrons do. They just peacefully overlap into a giant, dense, quantum fluid blob. The theoretical models of Boson stars anticipate that their��shape would be distorted by rotation in a way that differs from that of a spinning black hole.

By analyzing the data from GW241011, Vijaykumar and his colleagues presented compelling evidence that the primary object in the spinning binary was not distorted enough to fit the hypothetical model of a rotating Boson star – specifically, not the kind characterized by quartic self-interactions, effectively ruling out this exotic model for this event.

However, the mystery of Exotic Compact Objects is far from solved. The study notes that while certain Boson stars have been eliminated, other highly dense theoretical models—specifically those with an extreme “compactness” factor greater than 0.24 (black holes have compactness value of 0.5)—are still viable contenders for what this object might have been.

“This is a thrilling era for astrophysics,” says Vijaykumar. “With the increasing sensitivity of gravitational wave detectors like LIGO, Virgo, and KAGRA, we are no longer just guessing about what exists in the deep universe. We are actively stress-testing the standard model of particle physics and general relativity in real-time.”

The paper, led by Dr. Vijaykumar along with Dr. Tamara Evstafyeva (Perimeter Institute) and Dr. NV Krishnendu (University of Birmingham), places some of the most stringent constraints on beyond-Kerr black hole physics to date and establishes a vital new framework for how scientists will analyze future gravitational wave detections.

To read the full study��go to:. Phys. Rev. Lett. 137, 071402.

������Ƶ the Canadian Institute for Theoretical Astrophysics (CITA)
Located at the University of Toronto, CITA is a globally recognized research institute dedicated to advancing our understanding of the universe. CITA researchers specialize in theoretical astrophysics, cosmology, and fundamental physics, driving innovation in our understanding of black holes, dark matter, and gravitational waves.

SCIENCE CONTACT:��Dr. Aditya Vijaykumar

Media Contact:
Lyuba Encheva, Communications and Events Coordinator
Canadian Institute for Theoretical Astrophysics, University of Toronto
Email: communication@cita.utoronto.ca

August 17, 2026

April – May – June

If a single theme defined this quarter, it was community. At the end of May, we proudly celebrated CITA’s 40th anniversary, bringing together over 160 participants in person and hundreds more online from across the globe. The three-day conference��presented��forward-looking astrophysics��research but, just as much, it��felt��like a family homecoming.��We reflected on our founding ethos of collaboration and mutual support and celebrated the fact that��many��of the world’s leading tenured astrophysicists are CITA alumni. It is incredibly rewarding to see how our collaborative, theoretical approach continues to shape��the astrophysics field��worldwide.

We are immensely grateful to everyone who has made CITA the remarkable institution it is today.��Here’s��to the mysteries��we’ve��solved, the community��we’ve��built, and the next 40 years of theoretical astrophysics.

CITA@40: Celebrating 40 Years of Theoretical Astrophysics

05/27/2026: The Canadian Institute for Theoretical Astrophysics (CITA) marked its 40th anniversary at the University of Toronto at the end of May, bringing together astrophysicists from around the world for a three-day conference celebrating four decades of research,��training��and collaboration. More than 160 participants attended in person, with hundreds more joining online. The conference featured 87 speakers from 15 countries — including many former CITA postdoctoral fellows and graduate students who returned to share new research and reconnect with colleagues. A recurring theme throughout the celebratory event was the importance of academic community — with many attendees describing CITA as both a research hub and a formative “home” during their early academic careers. Words like “family” and “homecoming” were scattered through narratives of youthful times, full of enthusiasm for science and fun with friends.��CITA Director����opened the conference by welcoming participants and reflecting on the institute’s history. He noted that this meeting “brings together the three pillars of CITA: members of��the��CITA flagship in Toronto, the national network of affiliate faculty, and the global network of CITA alumni.”

U of T President Melanie Woodin highlighted CITA’s global reputation and paid tribute to the leadership of its founders,��Professors Richard Henriksen and Peter Martin, as well as its first directors, Scott Tremaine and Dick Bond.

Today, a significant percentage of the world’s leading tenured astrophysicists (more than 130) are CITA alumni, who have passed through the institute during their formative postdoctoral years. They carry CITA’s highly collaborative, theoretical approach to universities across the globe.

Back in Toronto for the CITA@40 conference, former postdoctoral fellows were happy to reunite with old friends and reminisce about the good times they had together.��Testimonies were shared by CITA alumni both in person and through individual video recordings:

Bernard Carr, Emeritus Professor of Mathematics and Astronomy at Queen Mary University of London, reflected in his video message on the first Kingston meeting he attended in 1986. His reminiscences of CITA highlighted both the lasting friendships he formed and his proud scientific collaboration with Dick Bond. He reflected on both the happy and the sad times he experienced at��CITA, and��reminded us to “remember those who played such an important role in CITA’s scientific achievements.”��

Doug Johnstone, current��President’s Science Advisor and PREAC Secretary at the National Research Council of Canada, (CITA postdoc in 1995) also shared in a video greeting: “The support of the CITA family was crucial for my decision to stay in the field. CITA was a fantastic place for us, and I hope it still is for the current CITA postdocs.��While at CITA, I got to know Shantanu Basu very well. We built our own research��niche��that began with��a��star formation conference. We did a second version of it last year. It has been a joy to��work with Shantanu ever since the 90s.”

John Lattanzio��and��Mike Fitchett��– the first two CITA postdoctoral fellows��who��joined in 1985– also sent a very long video greeting with highlights from the dawn of times, when “everyone did extra jobs”,��“everyone dressed very formally”,��and Peter Martin was an Acting Director, but “he did more acting than directing, and we all loved him!”.��“We did a lot of science and had great fun together”,��said John and Mike, and recommended the same approach to postdocs for years to come – “Have fun and do good science!”

Andrew��Jaffe, professor at Imperial College, shared in his video message that “CITA was, and still is,��a great place for postdocs to��become independent researchers.”��Reflecting on his scientific career, he spoke about his work��analyzing CMB data and added��“understanding Dick’s work over the years has been an honor and a pleasure��of my scientific career”.

Zhiqi Huang, Professor in Sun Yat-sen University expressed his gratitude to all��CITAzens, with special thanks to his mentors Dick Bond and Lev Kofman, “Their passion and curiosity have kept me on a��life-long��journey of discovery”.

Henk Hoekstra, professor in Leiden University, and his wife��Melanie, a former CITA staff member, visited CITA shortly before the event. In their video message, they shared that “so many memories came back”,��reflecting “great time at CITA back 25 years ago”.

Margaret Fukunaga, CITA’s founding staff member, reflected in her letter to��CITAzens��that her role was to “assure the faculty members who were serving as director that the administrative machine was strong and could keep on carrying CITA.” She expressed her gratitude to the faculty members for their trust in the business officers and in her successors.��Along with recalling many memorable and enjoyable moments at CITA, Margaret highlighted what she considered her greatest accomplishment: “to see a postdoc return to CITA as the Interim Director”.

A heartfelt thank you to all the alumni who traveled from near and far to join us for CITA@40! Hearing your stories from the institute’s early days and watching old friends and former colleagues reunite was a moving testament to the community we have built together over the last four decades. We are incredibly grateful for your warm notes of congratulations and for��remaining��such an integral part of the CITA family.

For those who were unable to attend the conference and/or banquet, we invite you to revisit the celebration through the photos captured during the event. You can also enjoy a��video from��CITAzens��around the world who were unable to join us in person.

Research and Publication Highlights

4/1/2026:��New Study Finds Evidence of Cosmic Explosions with Missing Black Holes

In a paper just published in��, CITA researchers Professor��Maya Fishbach��and postdoctoral fellows��Aditya Vijaykumar��and Amanda Farah, confirm that black holes with masses larger than 45 times the mass of the sun are the result of previous black hole mergers, rather than the collapse of enormous dying stars.

4/16/2026:��How a Cosmic Cloud Becomes a Solar System: Scientists Discover the “EnDTranZ” Missing Link

An international team of researchers—including CITA’s Interim Director,��Shantanu Basu—has just published groundbreaking findings in the Astrophysical Journal that solve a decades-old mystery in star formation.��We’ve long known that planets form in flat, spinning disks of gas and dust around young stars. But exactly how the material falling from the massive outer cloud “hits the brakes” and organizes into a stable, spinning disk has been a major puzzle.��Led by��Dr. Indrani Das��at the Academia Sinica Institute of Astronomy and Astrophysics, the team discovered the missing link: EnDTranZ  (Envelope Disk Transition Zone).

6/3/2026:��Supercomputer Reveals How Exploding Stars “Stir” the Galaxy from the Bottom Up

New research performed on the Trillium/SciNet Supercomputer at the University of Toronto reveals a fundamentally different mechanism by which exploding stars shape the turbulent structure of our galaxy. The study, authored by Dr. James Beattie, postdoctoral fellow at CITA, was accepted for publication in . It challenges long-standing assumptions about how turbulence is generated and sustained in the interstellar medium.

6/26/2026:��

Microlensing surveys have discovered plenty of regular exoplanets, but more surprisingly,��they’ve��also turned up many solo Neptunes with no star nearby. That��there are more free-ranging Neptunes than stars��is��unsettling, and astronomers��aren’t��sure how��so��many planets ended up��isolated. New research by��Sam Hadden��(CITA) and��Yanqin��Wu��(University of Toronto) presents an alternative idea: what if at least some of these free-floating planets aren’t fully on their��own, but��remain��weakly bound to their parent stars?��The paper “Free Floating or Merely��Detached?,” by Sam Hadden and��Yanqin��Wu��was recently featured by��AAS Nova:��2026 ApJ . 

Events and Workshops

4/17/2026:��In mid-April CITA welcomed����– a group of 32 undergraduate students, all majoring in astronomy at the��University of Groningen��in the Netherlands. The visitors travelled across the ocean to meet with CITA researchers and learn about current projects at the institute.��Designated��hosts were��CITA Graduate student��Alicia Savelli��and��Postdoctoral Fellows��Vera Delfavero,��Sebastiano D. von Fellenberg��and��Biprateep Dey.

5/4/2026:��Welcoming the new cohort of��SURFers��(Summer Undergraduate Student Fellows) at the��Canadian Institute for Theoretical Astrophysics��today. Supervisors and students are excited to meet and start planning their research collaborations. Summer is starting!
Supervisors this year are��Shantanu Basu, Pratika Dayal,��Rohan Dahale,��Radhika Achikanath Chirakkara,��Haowen Zhang,��Sebastiano D. von Fellenberg,��Yanlong Shi.

4/20/2026: 35 of the world’s leading experts in gravitational astronomy gathered at the CITA Flagship in Toronto for the��GWTC-6: The Bleeding Edge of Gravitational-Wave Populations��– a three-day workshop that took place between April 20 and 22. Researchers from Europe, Australia, UK, US, and Canada have been diving deep into recently released data sets, providing real-time feedback on preliminary results, and charting out new pathways to align theoretical models with observations. A huge thank you to the driving forces behind this event, our organizers: Amanda Farah and Aditya Vijaykumar are the main organizers of the ‘GWTC-6: The Bleeding Edge of Gravitational-wave Populations’, along with faculty members Maya Fishbach and Reed Essick.

Other CITA Supported Conferences in Q2:

June 4-5, 2026: ��Sampling, Simulation, and Scientific Discovery, University of Toronto. Organizers: Reed Essick, Maya Fishbach, Josh Speagle.

June 19-20, 2026: , McGill University. Organizers: Simon Caron-Huot, Robert Brandenberger, Manu Paranjape.

June 29 – July 3, 2026: , Université de Montréal. Organizers: Julie Hlavacek-Larrondo, Martin Bureau, Daryl Haggard.

Distinctions and Awards

4/28/2026: Congratulations to CITA Inc member Professor , University of Victoria, who was recently recognized by as the 2026 recipient of the Carlyle S. Beals Award for outstanding scientific achievement. Professor Babul is a world-renowned leader in physical cosmology, known for his work on the assembly, evolution, and physics of galaxy groups and clusters. Throughout his career, Professor Babul has contributed to several ground-breaking discoveries which have reshaped the field of cosmology, including being one of the first to recognize that radiation from early stars and quasars could significantly influence the evolution of cosmic structures.

4/28/2026: Congratulations to CITA Inc member Professor Michel (Mike) Fich, who was announced by����as the recipient of the��2026 Dunlap Award��for Innovation in Astronomical Research Tools.��This award recognizes his sustained and visionary leadership in developing and ensuring Canadian participation in groundbreaking infrared and mm-scale astronomical instrumentation.

6/26/2026:��Congratulations to CITA graduate student����and a Junior Fellow at����for��receiving��this year’s��Van Kranendonk Teaching Assistant Award��from the Department of Physics at the University of Toronto.��The award��reflects��not only strong subject��expertise, but also the ability to inspire, support, and elevate the student learning experience, an impact that often extends far beyond the classroom.

July 13, 2026

Originally published by .

The Canadian Institute for Theoretical Astrophysics (CITA) marked its 40th anniversary at the University of Toronto at the end of May, bringing together astrophysicists from around the world for a three-day conference celebrating four decades of research, training and collaboration.

More than 160 participants attended in person, with hundreds more joining online.

The conference featured 87 speakers from 15 countries — including many former CITA postdoctoral fellows and graduate students who returned to share new research and reconnect with colleagues.

A recurring theme throughout the celebratory event was the importance of academic community — with many attendees describing CITA as both a research hub and a formative “home” during their early academic careers. Words like “family” and “homecoming” were scattered through narratives of youthful times, full of enthusiasm for science and fun with friends.

, CITA’s director and a professor of astrophysics at Western University, opened the conference by welcoming participants and reflecting on the institute’s history. He noted that this meeting “brings together the three pillars of CITA: members of CITA the flagship in Toronto, the national network of affiliate faculty, and the global network of CITA alumni.”

U of T President Melanie Woodin highlighted CITA’s global reputation and paid tribute to the leadership of its founders, Professors Richard Henriksen and Peter Martin, as well as its first directors, Scott Tremaine and Dick Bond.

Woodin said it is rare for her to travel without hearing about “CITA’s outstanding success and legacy of scientific discovery,” adding that U of T was chosen to host the institute because of its commitment to leadership and fundamental science.

Stephen Wright, dean of the Faculty of Arts & Science, congratulated CITA on four decades of “training the next generation of explorers and leaders in the field of astrophysics.”

Nobel laureate — and guest of honour — said, “Over the years, it has been an education for me to interact with CITA researchers and friends, and I am very pleased to be here for their anniversary.”

McDonald, co-recipient of the for his work on neutrinos and a professor emeritus at Queen’s University, shared the prize for research demonstrating that neutrinos have mass, a discovery that reshaped understanding of fundamental particle physics.

Founded in 1984 to address a gap in Canada’s research landscape — at a time when the country had strong observational astronomy but no centralized hub for theory — CITA is administered by the Faculty of Arts & Science and operates both as a University of Toronto department and as an independent national research corporation.

Richard Henriksen, a co-founder and former chair of the CITA Council, recalled early efforts to strengthen Canada’s theoretical astronomy. Working with Peter Martin, he helped lead the successful campaign — officially endorsed in 1983 — to establish a national institute at U of T, formally created on June 21, 1984, with NSERC support.

From the very beginning, CITA adopted a distinctive model focused on postdoctoral training.

Rather than building a large permanent faculty, the institute emphasized recruiting top early-career researchers from around the world for fixed-term appointments, creating a dynamic research environment with a constant influx of new ideas.

Scott Tremaine, recruited from MIT as CITA’s first director in 1985, said the model was a major attraction. He described the institute as unique both as a national centre for theoretical astrophysics and for its emphasis on postdoctoral researchers at a pivotal early-career stage.

CITA’s research scope has evolved alongside major developments in astrophysics. Early work focused on galaxy formation, star formation and planetary dynamics, supported by increasingly sophisticated computational tools.

Over time, the institute developed advanced simulation capabilities that significantly contributed to the expansion of Canada’s supercomputing infrastructure.

In recent years, CITA researchers have been involved in emerging areas such as multi-messenger astrophysics, fast radio bursts and . The institute has contributed to projects including the CHIME telescope in British Columbia and has expanded into fields such as exoplanet research and early-universe cosmology.

Despite its incredible scientific impact, speakers at the anniversary celebration emphasized that CITA’s long-term success is closely tied to its supportive and collaborative culture. Former postdoctoral fellows described an environment characterized by intellectual freedom, trust and strong professional and personal connections.

Philip Armitage, now a professor at Stony Brook University and a research scientist at the Flatiron Institute, reflected on his time at CITA, highlighting both the academic opportunities and the supportive atmosphere.

Doug Johnstone, now science adviser to the president of the National Research Council of Canada, said in a video greeting that the “support of the CITA family” played a key role in his decision to remain in astrophysics.

Today, more than 130 CITA alumni hold tenured positions at institutions around the world, underscoring the institute’s global influence. Many of them returned to Toronto for the anniversary, reconnecting with colleagues and reflecting on the institute’s role in shaping their careers.

June 3, 2026

How do you map out the entire universe? For University of Toronto astrophysicist Dick Bond, you do it with five decades of passion, groundbreaking math, and a healthy dose of curiosity.

A fascinating new feature by the University of Toronto looks back at Bond’s legendary 50-year career—and his massive role in putting Canada on the global astrophysics map.

If you’ve ever heard the terms “cosmic web” or “gastrophysics” (how gas clouds transform into stars and planets), you have Bond to thank; he coined them. Decades ago, his theoretical models predicted the age, shape, and composition of our universe long before satellite technology could actually prove him right.

Beyond his equations, the article highlights Bond’s incredible impact as a mentor to over 200 researchers and his long-time leadership at the Canadian Institute for Theoretical Astrophysics (CITA), which celebrates its 40th anniversary this year.

At 75, Bond says he’s still making progress—and his best work is yet to come.

Read the full profile on ��to dive into his journey, his thoughts on the future of quantum physics, and his advice for the next generation of scientists.

Find more information on the history of the Cold Dark Matter (CDM) paradigm in this VIDEO by the.

The recording features talks by five scientists who played key roles in the early development and establishment of the Cold Dark Matter (CDM) paradigm.��Richard Bond,��Ken Freeman,��Jim Peebles,��Joel Primack, and��Mike Turner��came together for this panel discussion at the��2018 Physics of Galaxy Scaling Relations and the Nature of Dark Matter Conference��held at��Queen’s University. The discussion provides a valuable first-hand account of the origins, development, and early reception of CDM.

June 1, 2026

New research performed on the at the University of Toronto reveals a fundamentally different mechanism by which exploding stars shape the turbulent structure of our galaxy. The study, authored by , postdoctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA), was accepted for publication in . It challenges long-standing assumptions about how turbulence is generated and sustained in the interstellar medium.

Turbulence—the chaotic, swirling motion of gas—is a fundamental process in astrophysics, influencing everything from star formation to the transport of energy and magnetic fields across galaxies. For decades, scientists have largely assumed that turbulence in the Milky Way follows a classical cascade: energy injected at large scales breaks down into progressively smaller eddies (vortices or “swirls”), consistent with the well-known Kolmogorov picture.

However, this new work demonstrates that supernova remnants—the expanding shells of gas left behind by stellar explosions—can instead inject turbulence at small scales that, then, propagates upward to larger scales through an inverse cascade. This finding suggests that the dominant source of galactic turbulence may not operate in the way previously thought. Instead of a top-down energy transference (dying out of energy), it’s a��bottom-up build-up. His research shows that supernova explosions create microscopic, chaotic swirls first. Those tiny swirls then merge and push their energy��upward, eventually creating the massive, large-scale turbulence that shapes our entire galaxy.

“Our results show that the structure of turbulence in the galaxy carries a direct imprint of the physical instabilities that occur in supernova remnants,” said Dr. Beattie. “Rather than simply decaying or cascading downward, turbulence generated at the interfaces within these remnants can grow and reorganize, ultimately influencing dynamics on galactic scales.”

The research identifies the contact discontinuity—the unstable boundary between hot, shocked ejecta and cooler surrounding gas—as a key site of turbulence generation. Instabilities and strong baroclinic effects at this interface drive the formation of vortical motions that seed turbulence at relatively small spatial scales. From there, nonlinear interactions transfer energy to larger scales, producing a turbulent spectrum that deviates significantly from classical expectations.

Crucially, these results were made possible by cutting-edge numerical simulations performed on the Trillium Supercomputer, one of Canada’s most advanced high-performance computing systems operated by SciNet at the University of Toronto. The scale and fidelity required to resolve both the small-scale instabilities and their large-scale consequences demand computational resources at the forefront of modern supercomputing.

This revised picture has broad implications. It provides a new framework for interpreting observations of interstellar turbulence, including velocity fluctuations and magnetic field structure, and may help explain why measured spectra in the Milky Way often differ from theoretical predictions. It also suggests that models of galaxy evolution and star formation may need to be re-evaluated to account for this alternative turbulent driving mechanism.

Beyond its implications for the Milky Way, the work points to a more general principle: that microscopic plasma processes and instabilities can leave lasting imprints on macroscopic astrophysical systems.

“This is a shift in perspective,” Dr. Beattie added. “If turbulence in galaxies is seeded at small scales by physical instabilities, then understanding those instabilities becomes essential for understanding the large-scale universe.”

The paper is available on arXiv:��

Beattie, J. 2026,��American Astronomical Society,��,��,��,��Supernovae Drive Large-scale, Incompressible Turbulence through Small-scale Instabilities.��

SCIENCE CONTACT: Dr. James Beattie

Media Contact:
Lyuba Encheva, Communications and Events Coordinator
Canadian Institute for Theoretical Astrophysics, University of Toronto
Email: communication@cita.utoronto.ca