Simulations suggest starlight pressure clears gas, making early galaxies look brighter

By the Everything Space news desk · 04 Nov 2026 · written from the sources below

Image: Phys.org

New modeling indicates ultraviolet radiation from young stars can blow away dust and gas between stars, helping explain why JWST sees so many unexpectedly bright early-universe galaxies.

Researchers at the Flatiron Institute and the University of Texas at Dallas say they've found a possible explanation for why the James Webb Space Telescope has spotted far more bright galaxies in the early universe than expected: intense ultraviolet radiation from young star clusters may be blasting away obscuring gas and dust, acting like a cosmic leaf blower.

The team's findings, published in The Astrophysical Journal, focus on a type of ultraviolet light called Lyman-alpha radiation, which is generated when electrons collide with or combine with hydrogen. Unlike most radiation, Lyman-alpha light gets absorbed and re-emitted by hydrogen atoms at the same wavelength over and over, letting it build up significant pressure as it bounces through gas before finally escaping.

By analyzing snapshots from an existing simulation of a star-forming region in the early universe, the researchers calculated how much force this radiation pressure could exert on surrounding material. They found that in dense regions, gravity was strong enough to keep gas and dust bound in place despite the radiation push, meaning star formation likely wasn't significantly disrupted there.

However, in lower-density regions between stars, the radiation pressure was strong enough to overcome weaker gravitational pull, launching gas and dust outward at high speed and effectively clearing a path for light from stars to escape the galaxy.

The researchers say this clearing effect could help explain the surprising brightness of early galaxies observed by Webb, since removing light-blocking material between stars would make those galaxies appear more luminous than they might be with denser surrounding gas and dust.

The study's authors note that more work is needed to understand the nature of dust in the early universe and to build simulations that fully combine Lyman-alpha radiation, gas movement, and star formation together. Current efforts have managed to model these interactions in two dimensions, and researchers hope that advances in computing power will eventually allow three-dimensional simulations of the phenomenon.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.