ASJ Young Astronomer Award for Sunmyon Chon
This year, the Astronomical Society of Japan (ASJ) awarded the ‘Young Astronomer Award’ to MPA postdoc Sunmyon Chon for his work on “Theoretical Studies on the Evolution of the Initial Mass Function of Low-metallicity Stars in the Early Universe”. The ASJ highlighted “his significant contributions to theoretical astrophysics, particularly regarding star formation in the early universe, a topic he has advanced through simulations using the National Astronomical Observatory of Japan's supercomputer ATERUI II.”
The advent of large-aperture telescopes in recent years, including the James Webb Space Telescope (JWST), has made it possible to observe star-forming galaxies and supermassive black holes in the early universe. Reports indicate that the masses, luminosities and number densities of the observed galaxies and black holes differ significantly from conventional theoretical predictions. Star formation in low-metallicity environments is key to elucidating the formation of these early-universe objects. In particular, the initial mass function (IMF) of stars is an extremely important quantity, relating to heavy-element contamination from supernova explosions, radiative feedback such as the heating of surrounding gas, and even the formation of supermassive black hole seeds.
Sunmyon Chon has been working to elucidate the star formation processes in the early universe with multi-scale numerical simulations from cosmological scales and the formation of large-scale dark matter structures to (astronomically) small scales at which star formation occurs. Through his realistic modelling, he became the first in the world to clarify systematically the changes in the IMF due to differences in heavy-element abundance across a wide range, from the first-generation stars to the heavy-element abundance of the local universe.
These results suggest that massive stars may form in a wider variety of environments than previously anticipated, and have significant implications not only for star formation but also for galaxy formation in the early universe. Furthermore, JWST observations released since 2023 have confirmed a large number of bright galaxies in the universe at redshifts exceeding 10, which surpass conventional star-formation models; Sunmyon Chon’s research findings are attracting attention as a leading theory to explain these observations.
Furthermore, he also investigated the formation of supermassive stars under extreme conditions – which are one of the leading candidates for the seed black holes of supermassive black holes. With his ultra-high-resolution fluid simulation, termed the ‘supercompetitive accretion’ model, he showed that supermassive stars could form even in low-metallicity environments. This scenario could represent a universal origin for all supermassive black holes, not limited to the early universe. In recent years, observations by the JWST have revealed that the number of black holes in the early universe far exceeds previous predictions, further increasing the significance of this work.
Established in 1988, the Astronomical Society of Japan (ASJ) awards the ‘Young Astronomer Award’ annually to up to three young researchers, under 35 years of age, who have made significant accomplishments in astronomy. In their laudation, the ASJ recognized him as “a young researcher who is expected to continue making significant contributions to the formation of stars and celestial bodies spanning the early universe, and from whom great things are expected in the future.”
