Overview
- A peer-reviewed Nature Astronomy paper published Aug. 18, 2026 used exceptionally deep JWST infrared spectra combined with earlier VLT data to study nine massive, quiescent galaxies seen about seven billion years after the Big Bang.
- The team measured subtle absorption features in the combined spectra that match fingerprints of many faint, low-mass stars and infer a bottom-heavy initial mass function in several of the galaxies.
- In individual cases the revised stellar-population mix raises stellar-mass estimates by factors of roughly three to four compared with masses computed using a Milky Way–like IMF.
- If the same bottom-heavy IMF applies to the very-high-redshift galaxies JWST found, their true masses could be much larger and that would deepen the puzzle of how such large systems formed so quickly.
- Authors say the result affects cosmic stellar-mass budgets and prospects for early planet-hosting stars but caution the sample is small and follow-up spectroscopy at higher redshift is needed to test for systematic effects.