Prof. Lee’s main research field is extragalactic astronomy and observational cosmology with a focus to understand how galaxies in various environments form and evolve.

Galaxies are considered to be building blocks of the universe. Galaxies are gigantic systems including luminous stars and interstellar medium as well as dark matter and supermassive black holes. Deep images of the universe illustrate a variety of galaxies in color, size, and luminosity. Some galaxies are large and bright with beautiful colors, while some are dwarf galaxies which are barely recognizable. Galaxies are often bound in galaxy groups, galaxy clusters, and superclusters of galaxies, and a few of them are found in voids which are huge empty structures.

Prof. Lee is using multiwavelength photometric and spectroscopic data to study physical and chemical aspects of stars, star clusters, and interstellar medium in galaxies with various scales and types. He is trying to figure out how large scale structures from star clusters to galaxy clusters form.

Prof. Lee also carries out a research to measure the distances to galaxies. He is using a tip of the red giant branch (TRGB) method which is much more efficient than Cepheid variable stars. He is trying to improve the calibration of the luminosity of Type la supernovae, and obtain a more reliable value for the Hubble Constant which represents how fast the universe is expanding.