Caption
Present-day disk galaxies often contain a thick, star-filled outer disk and an embedded thin disk of stars. Three major theoretical scenarios have been proposed by astronomers to explain how this dual-disk structure comes to be. Using archival data from the James Webb Space Telescope, a team of astronomers is closer to understanding disk galaxies’ origins, and the stellar thick- and thin-disk formation process. The team carefully identified, visually verified, and analyzed a statistical sample of more than 100 edge-on disk galaxies at various periods — up to 11 billion years ago (or approximately 2.8 billion years after the big bang). The results of their analysis suggest that galaxies form a thick disk first, followed by a thin disk. The timing of this process depends on a galaxy’s mass: high-mass, single-disk galaxies transitioned to two-disk structures around 8 billion years ago, while low-mass, single-disk galaxies formed their thin disks about 4 billion years ago.
