A sci-fi fan since young adulthood, Rixin Li found himself among the many inspired to study planetary science when, in the early 2010s, NASA’s Kepler Space Telescope began detecting thousands of exoplanets. A few years later, he would conduct sophisticated numerical modeling to explain how such planets could form, illuminating their leap from tiny dust and ice particles to planetesimals—or bodies of solid materials, such as asteroids. Using code he developed, Rixin has described how conditions of the protoplanetary disk surrounding a young star influence planetesimal demographics. In doing so, he successfully linked his findings and predictions to properties observed in the Kuiper Belt, a region of our solar system highly populated with leftover planetesimals. He also revealed that particles require much less density for the clumping and gravitational collapse preceding planetesimal formation than once widely accepted.

During his fellowship, Rixin will use novel computational algorithms to model the complex dynamics of gas, dust, and planetesimals within protoplanetary disks at various evolutionary stages. In particular, he seeks to examine phenomena in large, young disks, to confirm recent observations that planet formation may be underway at very early stages. He aims to sharpen conventional theories to guide future observations—and to create a more coherent planet-formation picture for solar systems across the galaxy. Rixin received a Ph.D. in astronomy and astrophysics from the University of Arizona in 2020. Prior to starting his 51 Pegasi b Fellowship, he was a postdoctoral research associate at the Cornell Center for Astrophysics and Planetary Science.

“How do dust and ice particles just millimeters in diameter become planetesimals to form the core of future planets? It’s a big jump. Having a coherent model for this process is key to connecting all stages of planet formation.”