A new survey led by the University of Utah, using the Hubble Space Telescope, is offering fresh insights into how massive stars influenced the formation and evolution of early galaxies. The survey, named the Treasury of Extremely Metal-Poor O Stars (TEMPOS), uses ultraviolet (UV) observations from Hubble's Cosmic Origins Spectrograph (COS) to study massive stars in nearby dwarf galaxies. These galaxies are considered the closest analogs to those in the early universe, which had much lower levels of heavy elements. The survey's large dataset could help scientists improve models of massive stars, which are essential for interpreting data from the James Webb Space Telescope, launched in 2021. Massive stars, those with masses more than 10 times that of the Sun, are rare but play a crucial role in shaping galaxies. They emit intense radiation, shed material through stellar winds, and eventually explode as supernovae. These processes influence the evolution of their host galaxies by heating and regulating the gas that can later form new stars. Astronomers use the term "metallicity" to describe the abundance of elements heavier than hydrogen and helium. The early universe had far fewer heavy elements than today's galaxies, such as the Milky Way, meaning the stars that formed back then likely had different physical properties. Rather than studying the Milky Way, the TEMPOS survey focused on nearby dwarf galaxies, which have lower metallicities similar to those found in the early universe. The survey studied 29 massive stars across six local dwarf galaxies, all with metallicities below one-fifth that of the Sun. UV light provides detailed information about the elements in a star's atmosphere and the winds that continuously expel material from its surface. Observing these faint stars outside the Milky Way required extensive telescope time, with each star observation taking up to 35 hours. The survey combined new observations of 12 stars with previously collected data to create a more comprehensive dataset. Massive stars lose mass through stellar winds, and the strength of these winds depends on metallicity. Lower-metallicity stars are expected to have weaker winds and lose less mass over their lifetimes. The TEMPOS findings confirmed this trend but showed that at the lowest metallicities—below about 10% of the Sun's—the wind speeds drop more sharply than expected. This could mean that extremely metal-poor stars retain more of their original mass, affecting how they evolve and shape their galaxies. Iron, a key element in stellar processes, was also studied, with the team measuring iron absorption in UV spectra to better understand variations in metallicity. The data suggest that metal-poor stars have a wide range of iron abundances. The TEMPOS team, led by researcher Telford, previously studied three stars in detail but found it difficult to detect broader trends with such a small sample. The new survey provides the largest dataset of its kind, offering a more robust foundation for future research. Researchers are now combining Hubble's UV data with visible-light observations from Hawaii's Keck Observatory to model the stars in greater detail. These combined datasets will help measure properties like chemical abundances and mass-loss rates, which could aid in interpreting observations from the James Webb Space Telescope. The UV spectra collected by TEMPOS will also be publicly available, allowing scientists worldwide to explore additional questions about massive stars and their role in galaxy evolution.