Astronomers using NASA/ESA/CSA’s James Webb Space Telescope have discovered an unexpectedly large number of faint, low-mass stars in distant galaxies, suggesting that some of the largest galaxies in the early universe may have up to four times the previously estimated mass.
“These galaxies are unique,” says study co-author Dr. Joel Reja, an astronomer at Pennsylvania State University.
“They stand out because of their unexpected size. They contain three to four times more mass than previously thought, making them much more massive.”
For this study, Leya and colleagues examined detailed spectra of nine massive, mature galaxies that ceased star formation billions of years ago in the early universe.
They found that these galaxies house significantly larger populations of small, faint, low-mass stars than previously believed, resulting in a system that is actually three to four times heavier than earlier estimates.
This challenges the conventional notion that stars form uniformly in size everywhere and deepens the mystery of how such massive galaxies quickly formed after the Big Bang.
It also implies that there may have been more low-mass stars, and potentially more planets, in the early universe than previously theorized.
“Imagine the galaxy as a city, where the brightest stars are the skyscrapers visible from afar,” says lead author Chloe Chen, a PhD graduate at Leiden University.
“Our model reveals a substantial population of low-mass stars hidden behind these rare, bright stars, akin to hidden houses among skyscrapers.”
“The findings indicate that this galaxy is much larger than previously thought.”
“Until recently, such measurements were not feasible,” states co-author Marce Slob, a doctoral candidate at Leiden University.
“We required a telescope with the capacity to zoom into distant galaxies, along with high-quality spectra and new analytical methods to accurately identify the faint, low-mass stars concealed within these cosmic behemoths.”
The research team asserts that this discovery carries significant implications for our comprehension of the early universe.
“This outcome demonstrates that there is more mass hidden in low-mass stars than previously assumed,” notes co-author Professor Mariska Kriek of the Leiden Observatory.
“This has implications across various astronomical disciplines. For instance, many planets orbit low-mass stars, suggesting that more planets may have emerged in the early universe than previously believed.”
A paper detailing these findings was published in the journal Nature Astronomy on August 18th.
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CM Chen others. Hidden mass of early galaxies revealed by bottom-heavy initial mass function. Nat Astronpublished online on August 18, 2026. doi: 10.1038/s41550-026-02932-4
Source: www.sci.news
