How do disc galaxies grow? 🌀 Many galaxies we see today — including our own Milky Way — have two main components: a thick, star-filled outer disc and a thinner, brighter inner disc. But how did this dual-disc structure come to be? Thanks to archival data from esawebb, astronomers have taken a major step toward solving the mystery. By studying over 100 edge-on disc galaxies — some seen as they were 11 billion years ago — researchers found a clear pattern. It turns out galaxies likely form a thick disc first, followed by a thin one. The timing of this transformation depends on the galaxy’s mass. Massive galaxies began forming their thin discs around 8 billion years ago. Smaller galaxies took longer, adding their thin discs about 4 billion years ago. This carousel shows two groups of galaxies seen by Webb: - Those with both thin and thick discs - And those still in their thick-disc-only phase Each galaxy appears edge-on, like a cosmic line of light stretching through space — offeri...