Astronomers have found that some of the universe's most massive stars may release far weaker stellar winds than existing models predicted. The discovery could refine how scientists understand the growth of the first galaxies.
Using the Hubble Space Telescope, a research team studied 29 exceptionally hot, luminous O-type stars in six nearby dwarf galaxies. These galaxies contain very low levels of elements heavier than hydrogen and helium, conditions that offer a useful comparison with the chemically young universe.
Stellar winds weaken faster than expected
Massive stars continually push gas into surrounding space through stellar winds. These outflows are powered by radiation interacting with heavier elements, known to astronomers as metals. As metal content falls, scientists expect winds to become less powerful.
The observations confirmed that trend but also identified a notable threshold. Below roughly 10% of the Sun's metal abundance, stellar winds appeared to decline more sharply than theoretical predictions suggested.
The programme, called TEMPOS--Treasury of Extremely Metal-Poor O Stars--focuses on stars in environments with chemistry closer to that of ancient galaxies. While these objects are not relics from the first generations of stars, they allow researchers to measure stellar behaviour under similarly metal-poor conditions.
A clearer view of galactic evolution
When powerful winds are reduced, massive stars may retain more material during their lifetimes. That shift can influence how they evolve, how much energy they return to surrounding gas, and how effectively young galaxies create later generations of stars.
The team is combining Hubble data with observations from the Keck Observatory to examine mass loss in greater detail. Published in The Astrophysical Journal Supplement Series, the research provides an important benchmark for interpreting distant galaxies observed by modern space telescopes.
As astronomers build more precise models of low-metal stars, these measurements could help reveal how the earliest galaxies assembled, transformed gas and illuminated the young cosmos.
