How big can the universe's first starbursts get?

As telescopes have grown more advanced, astronomers have discovered intriguing characteristics of the universe, yet a crucial element remains elusive: Population III (Pop III) stars. These first-generation stars were entirely composed of hydrogen and helium, without any heavier metals. A new study published on the arXiv preprint server examines the potential size of these starbursts and whether the James Webb Space Telescope (JWST) could detect one.

Although JWST has identified hints of these stars, they appear much later than predicted by earlier models. For this to occur, two challenges must be overcome: preventing premature collapse of hydrogen and helium gas clouds and avoiding contamination from metals from previous supernovae. The former issue is addressed by Lyman-Werner (LW) radiation, which can delay gas cloud collapse by dissociating molecular hydrogen, the primary coolant.

By modeling a cooling dark matter halo exposed to varying levels of LW radiation, researchers found that if a gas cloud absorbs LW radiation, star formation is delayed until the cloud reaches atomic cooling, allowing the formation of massive, metal-free Pop III starbursts. However, the presence of metals from earlier supernovae poses a risk, but these particles move more slowly than LW radiation, which can reach pristine gas clouds hundreds of millions of years earlier.

Gravitationally lensed surveys, like GLIMPSE, may detect up to nine late-blooming Pop III starbursts, potentially making this paper a reference point for future studies.