'Hidden stars' suggest that distant galaxies are much more massive than they appear
Astronomers have discovered that the most massive galaxies in the early universe contain far more small stars than expected. As a result, these early galaxies were likely much more massive than initial measurements suggested. This discovery challenges current understanding about how the first galaxies formed. The results are published today in Nature Astronomy.
Recent studies utilizing the James Webb Space Telescope (JWST) have revealed that some of the most massive galaxies in the early universe contain significantly more low-mass stars than previously estimated. This discovery challenges current models of galaxy formation, as these early galaxies are likely more massive than initially thought. The key to this finding lies in the ability of the JWST to detect the faint, low-mass stars hidden among the bright, massive stars in these galaxies.
The research team, led by scientists from Leiden University, examined nine mature galaxies that had ceased forming stars billions of years ago. By analyzing the light from these galaxies through spectroscopy, the researchers were able to determine the proportions of small, faint stars and large, bright stars for the first time. The bright, massive stars typically dominate the spectrum, making the low-mass stars difficult to detect.
However, the team's observations revealed that these galaxies contain a much larger fraction of low-mass stars than previously assumed.
The lead author, Chloe Cheng, compared the situation to a city with a skyscraper skyline, where the bright stars represent the skyscrapers that immediately catch the eye from afar. "The low-mass stars are like houses hidden between the skyscrapers," she explained. "Our models show that a far more numerous population of low-mass stars is concealed by those rare, bright stars." As a result, these galaxies turn out to be much more massive than previous estimates suggest.
For instance, one of the galaxies studied may have formed less than 1.5 billion years after the Big Bang and could be up to four times more massive than previously thought. These findings have significant implications for our understanding of the early universe. The researchers emphasize that galaxy formation models must now account for the rapid production of low-mass stars in the early universe.
Additionally, the discovery suggests that more planets may have formed around low-mass stars in the early universe than previously assumed.
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