JWST finds early galaxies may be 4 times more massive than thought

Astronomers using NASA's James Webb Space Telescope discovered that some of the largest galaxies in the early universe may have been four times more massive than previously estimated. The team, including researchers from Penn State, analyzed nine mature galaxies that had stopped producing new stars billions of years ago. By combining JWST observations with earlier data from the Very Large Telescope, they were able to estimate the proportion of small, faint stars and larger, brighter stars in these ancient galaxies for the first time.

These massive galaxies, which formed relatively soon after the Big Bang, contained a significantly higher proportion of low-mass stars compared to smaller galaxies like the Milky Way. This finding challenges long-standing assumptions about the relative proportions of stars in galaxies throughout the universe. The researchers used the JWST to separate the light from each galaxy into a spectrum, identifying the presence of small, dim stars hidden among the dominant, bright stars.

This breakthrough technique, enhanced by new analysis methods, allowed scientists to detect subtle signatures of these faint stars. The implications of this discovery extend beyond galaxy formation, potentially indicating that more planets may have formed in the early universe as well. As astronomers continue to study galaxies from earlier periods using the same technique, the findings could reshape our understanding of how galaxies evolved in the young universe.