Hidden faint stars make ancient galaxies far heavier than estimated
Using JWST and ground-based data, astronomers studied nine massive, mature galaxies from the early universe and discovered they contain many more small, faint stars than previously assumed. This hidden population could make these galaxies three to four times more massive than earlier estimates, complicating theories of galaxy formation. The findings also hint that planets around low-mass stars may have been more common in the early cosmos.
The research team combined JWST spectral observations with earlier data from the Very Large Telescope to analyze nine galaxies that had already stopped forming stars. By examining subtle color variations in each galaxy's light spectrum, they identified a higher proportion of low-mass stars than standard stellar population models typically predict.
One galaxy, which formed within 1.5 billion years of the Big Bang, may be up to four times heavier than earlier calculations suggested. This finding challenges the long-held assumption that star formation ratios were consistent across the universe, raising new questions about how quickly massive galaxies could assemble in the early cosmos.
This discovery could reshape how scientists model the early universe's evolution, potentially requiring revisions to galaxy formation theories. If ancient galaxies were significantly more massive, estimates of cosmic structure growth may need adjustment. The findings also hint that planets around low-mass stars may have been more common in the early cosmos, which could broaden our understanding of where planetary systems might form. For the public, this deepens our cosmic narrative without immediate practical effects, though it may influence future telescope missions and research priorities.