Observations from the Hubble Space Telescope of nearby compact starburst galaxies challenge a classic explanation for reionization, the phase in which radiation from the first galaxies ionized the neutral hydrogen filling the young universe. The study, published on 15 October 2026 in Nature Astronomy, indicates that supernova-driven winds did not clear the way for that light — and may even have blocked it.
What the team measured
The team led by Cody Carr, now a postdoctoral researcher at the University of Michigan, analysed Hubble spectra of nearby galaxies forming stars at an intense rate. These galaxies serve as local analogues of early-universe systems, not as direct observations of that era. By measuring galactic wind speeds and the fraction of ionizing radiation escaping, the researchers found an inverse relationship: the faster the winds, the smaller the fraction of light escaping.
A short window, before the explosions
According to the study, Lyman-continuum escape peaks within roughly the first 3 million years of a starburst, when radiation and winds from young, massive stars are already present but supernova-driven galactic winds have not yet fully developed. After that period, the explosions stir surrounding gas and dust, increasing the coverage of neutral material and suppressing radiation escape.
It is important to separate what was measured from what was interpreted. The observed result is the correlation between faster winds and lower escape in the sample galaxies. The idea that light mainly escaped before the first supernovae is the authors' proposed interpretation, and it still needs testing in more galaxies. The researchers themselves are seeking more Hubble observing time and warn that cosmological simulations need to incorporate radiation and winds from young stars before supernova activity begins.
Image credit: Painting by Siyi Wang, via Nanowerk. The image is a painting, not a photograph, showing massive stars emitting ionizing radiation while gas swept up by supernova winds may prevent its escape.
Sources: Nature Astronomy — “Lyman continuum escape during the onset of galactic winds in compact starbursts”; Nanowerk — “Supernova explosions may have blocked the light that transformed the early universe” (21 de outubro de 2026); Open Access Government — “Hubble observations challenge supernova role in early universe reionisation”
Transparency: this article was produced with the assistance of artificial intelligence, cross-checked against public posts on X and internet sources. Consult the original sources to verify the details.
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