A new study led by Tae Bong Jeon from the Cosmic Frontier Center at the University of Texas at Austin explores the potential size of the universe's first stars—known as Population III (Pop III) stars—and whether the James Webb Space Telescope (JWST) could detect them. These stars, which formed in the early universe from hydrogen and helium only, are thought to be extremely massive and short-lived. While the JWST has detected hints of these stars, they appear to have formed much later than earlier models predicted. Some galaxies at the end of the Epoch of Reionization, a period when the universe became transparent to light, show signs of these ancient stars, but the timing is hundreds of millions of years later than expected. The formation of Pop III stars depends on how primordial gas clouds cool. Molecular hydrogen (H2) is a key coolant in this process, allowing gas to condense and form stars. However, Lyman-Werner (LW) radiation, which consists of soft ultraviolet photons, can break apart molecular hydrogen, delaying star formation until the gas reaches a "atomic cooling" stage. In the study, researchers modeled a dark matter "halo" exposed to varying levels of LW radiation and found that the outer layers of the halo remained hot, while the inner core cooled and eventually formed a star. In addition to LW radiation, metals from nearby supernovae can influence the gas clouds. However, these metals spread more slowly than LW radiation. The study suggests that with the aid of gravitational lensing—where the gravity of a massive object bends and magnifies light from more distant objects—modern equipment could detect Pop III starbursts. However, gravitational lensing requires precise alignment between the lensing object and the distant starburst, which is relatively rare. The study estimates that surveys like GLIMPSE, which are designed to use gravitational lenses, could identify up to nine of these late-forming Pop III starbursts. These findings highlight the challenges of observing the universe’s earliest stars and the potential of combining advanced telescopes with natural cosmic phenomena like gravitational lensing to uncover the universe’s hidden history.