The bright galaxies found by the James Webb Space Telescope (JWST) in the very early universe could be the product of bursts of massive star formation — and it’s likely that this fact renders the galaxies more luminous than expected for the era in which they exist. This is the conclusion drawn by researchers who used computer simulations to model how these galaxies formed and began producing stars.

When the JWST began science operations in the summer of 2022, its deep observations of the universe quickly began turning up high-redshift galaxies. These are galaxies that seemed to have existed earlier in the universe than astronomers had ever seen before. In fact, the galaxies, which were seen as they were when the universe was less than 400 million years old,  appeared more luminous than what the standard model of cosmology predicts for the era. This led to claims that the standard model —which depicts galaxies starting off small and then growing hierarchically through mergers driven by filaments and haloes of dark matter in the cosmic web — must be wrong.