Welcome! I’m Zhiyuan Ji, a JASPER Scholar at the University of Arizona. I am an observational astronomer studying how galaxies formed, evolved, and eventually fell silent in the early universe.

My research focuses on the first massive quiescent galaxies — systems that built their stars with astonishing speed and then quenched within a cosmic heartbeat. Using the James Webb Space Telescope, ALMA, and Hubble, I explore how stars, gas, and dust interact to transform chaotic starbursts into the structured, quiescent galaxies that now dominate the stellar-mass budget of the modern universe.

At the heart of my work lies a fascination with structural transformation — how galaxies assemble their dense stellar cores, expel their gas, and grow into quiet elegance after the frenzy of formation. By connecting structure, dynamics, and interstellar physics across cosmic time, I aim to uncover how the Hubble sequence emerged and how order first took hold in the cosmos.

I also study galaxies that leak ionizing photons — the rare systems through which ultraviolet light escaped to reionize the early universe.