Play store
Astronomers are finding that some of the first galaxies in the universe do not behave as existing models predict. Researchers say one possible explanation is that the most massive stars in those galaxies evolved differently from similar stars in the modern Milky Way.
A new survey led by the University of Utah is using the Hubble Space Telescope to investigate the differences. The project, called the Treasury of Extremely Metal-Poor O Stars (TEMPOS), uses ultraviolet measurements from Hubble’s Cosmic Origins Spectrograph to study massive stars in nearby galaxies with conditions similar to those of the early universe.
The survey could help scientists improve models of massive stars and better understand how these stars shaped young galaxies.
The research is becoming more important as the James Webb Space Telescope continues to reveal complex galaxies from the early universe.
“Webb opened up a whole bunch of new questions about the evolution of these early galaxies — they’re weird,” said Grace Telford, an assistant professor of physics and astronomy at the University of Utah and lead author of the study.
“That’s the scientific motivation behind the TEMPOS program: to help understand what is going on in these early galaxies,” she said.
The survey was published on Sept. 21, 2026, in The Astrophysical Journal Supplement Series.
Stars more than 10 times as massive as the Sun are relatively rare, but they can have a major impact on their host galaxies.
They produce huge amounts of radiation, lose material through powerful stellar winds and eventually explode as supernovae.
“They burn very hot, bright and fast and they end their short lives as supernova explosions that deposit a lot of energy and material into the surrounding gas,” Telford said.
Such stars can heat and regulate the gas needed to form new stars, influencing the evolution of entire galaxies.
A key difference between early galaxies and modern galaxies is their chemical composition. Astronomers use the term metallicity to describe the abundance of elements heavier than hydrogen and helium.
The earliest galaxies contained far fewer of these heavier elements than galaxies such as the Milky Way. As a result, massive stars born in those environments may have had significantly different physical properties.
“Massive stars at low metallicity are particularly important for building accurate models of early galaxies,” Telford said. “And we can’t just study how metal-rich massive stars in the Milky Way behave to interpret those observations.”
