July 17, 2026
The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI)
The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI) Project Researcher Takafumi Tsukui has been named a recipient of the Astronomical Society of Australia’s (ASA) Louise Webster Prize, which recognizes outstanding research by a scientist early in their postdoctoral career. The award, announced on July 7 at the ASA’s Annual Scientific Meeting in Canberra, commends his work on how galaxies formed their disks during his postdoctoral fellowship at the Australian National University.
Large disc galaxies, including our Milky Way, often consist of two distinct structural components: a thin disc of younger stars nested within a thicker disc of older ones. When and how this two-layered structure forms has been debated for decades. Until now, it could only be studied in the Milky Way and nearby galaxies, in the present-day Universe.
Using the sharp vision of the James Webb Space Telescope like a time machine, Tsukui identified thin and thick discs in galaxies as far back as 10 billion years and traced how galaxies built their discs across cosmic history. His analysis revealed a clear sequence: in the early Universe, most galaxies had a single thick disc, and the thin disc formed later within it.
By adding the time dimension to a question previously studied only in today’s Universe, his work provides a major step toward resolving this decades-old puzzle. Tsukui’s measurements are already being used to test new theoretical models of how galactic discs form.
“I am deeply honored to receive this award. I am grateful to my collaborators, Emily Wisnioski, Joss Bland-Hawthorn, and Ken Freeman, as well as my colleagues and friends, without whose support this work would not have been possible. This recognition encourages me to continue exploring new aspects of galaxy formation that I hope people will find exciting,” Tsukui said.
Related links
Seven million cosmic alerts a night. Ghost galaxies hiding in plain sight, and other prizes (Astronomical Society of Australia / Science in Public)
About the Louise Webster Prize (Astronomical Society of Australia)
