JWST finds early galaxies may be 4 times more massive than thought
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Astronomers using NASA's James Webb Space Telescope found that some of the largest galaxies in the early universe contain far more small, faint stars than previously realized. The discovery suggests these ancient galaxies may be three to four times more massive than earlier estimates. The findings, published in Nature Astronomy, challenge long-standing assumptions about how the first galaxies formed.
Key Facts
- The study examined nine massive, mature galaxies that stopped forming stars billions of years ago, combining JWST data with ground-based observations from the Very Large Telescope.
- Joel Leja, associate professor at Penn State and coauthor, said the galaxies are 'three or four times more massive than we expected.'
- One galaxy, likely formed less than 1.5 billion years after the Big Bang, could be up to four times more massive than previous calculations suggested, according to coauthor Martje Slob of Leiden University.
- The findings were published in Nature Astronomy.
Hidden Stellar Populations
Researchers separated each galaxy's light into a spectrum to identify the types of stars present. Large, luminous stars dominate the light, while smaller stars are far dimmer and harder to identify. Lead author Chloe Cheng of Leiden University compared bright stars to skyscrapers that hide a far more numerous population of low-mass stars, like houses concealed between them. The team found that the most massive early galaxies contain a much greater share of low-mass stars than smaller galaxies such as the Milky Way.
Implications for Galaxy Formation
Astronomers have traditionally assumed that stars formed in roughly similar proportions throughout the universe. The new findings challenge that long-standing assumption. Penn State researchers contributed expertise and guidance for modeling the light detected from the galaxy systems.
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JWST finds early galaxies may be 4 times more massive than thought
