Hidden Stars Reveal the True Size of Ancient Galaxies in the Distant Universe, and It Isn't What We Expected

Webb spectra found an ancient massive galaxy packed with far more small, faint stars than expected, implying some of the universe’s earliest giants may be roughly four times heavier than astronomers calculated — deepening the mystery of how they formed so quickly

Astronomers cannot place a distant galaxy on a scale. They estimate its stellar mass from the light that reaches a telescope, then use a model to infer the stars too faint to contribute much of that light. That hidden part of the calculation may be much larger than expected in some ancient massive galaxies. Ultra-deep James Webb Space Telescope spectra of nine old, quiet systems indicate that several contain an excess of low-mass stars compared …

Hidden Stars Reveal the True Size of Ancient Galaxies in the Distant Universe, and It Isn't What We Expected

A recent discovery changes how we thought galaxies form and evolve over time.

JWST found ancient galaxies hiding four times their measured mass in small stars

James Webb’s spectrograph reads individual stellar populations the way a prism reads a flame. Point it at a distant galaxy, collect enough photons, and the resulting spectrum encodes not just which types of stars are present but in what proportions. That measurement was always theoretically possible; at the distances involved — light that left when the universe was less than 1.5 billion years old — no telescope had ever done it reliably. The Jam…