Lyman continuum escape during the onset of galactic winds in compact starbursts. Nature Astronomy.
Which way the winds blow
The researchers employed the Hubble Space Telescope to examine remote analogues of the ancient universe within our local cosmic neighborhood: six star-forming, wind-launching galaxies situated approximately 3.5 billion light-years away.
These compact starburst galaxies are generally smaller than 6,500 light-years in diameter and form around 10 solar masses’ worth of stars per year. This star-birthing rate exceeds that of the Milky Way by several times.
The galaxies’ spectra, which serve as light-based fingerprints, revealed the origin, chemical composition, velocity, and direction of their stellar winds – all generated by radiation from their newly formed stars.
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The investigators also described how these processes evolved as the massive young stars matured and died in energetic supernovae billions of years later, with the resulting galactic winds eventually surpassing the stellar winds.
These nearby galaxies highlighted a counterintuitive two-phase mechanism.
In the initial phase, occurring within the first 3 million years of star formation, the newly formed massive stars’ stellar winds carved through their galaxies’ neutral gas and dust at nearly 2,000 miles per second. This allowed Lyman continuum light to escape the galaxy and ionize neutral gas and dust in intergalactic space.
The second phase, emerging around 3 million years after star formation, appeared to reverse this process. As O-type stars – the hottest, bluest, and most massive stars in the cosmos – lived fast and died young, their expelled stellar material added to the opaque galactic gas and dust, creating traps for Lyman continuum light.
Older galaxies in this study – and consequently those with faster supernova-generated galactic winds – permitted the least amount of ionizing radiation to escape their surroundings.
“Our findings generally disagree with most cosmological simulations, which typically show the Lyman continuum escape fraction peaking after the launch of supernova-driven winds,” explained Carr via email. In essence, supernovae did not drive the Epoch of Reionization but may have moderated it. The intense light from newborn stars now appears to be the primary source of reionization.
Future research could aim to collect additional galactic samples and conduct higher-resolution observations across other wavelengths.
Carr, C., Cen, R., McCandliss, S., Ford, J., Saldana-Lopez, A., Scarlata, C., Huberty, M. S., Jaskot, A., Flury, S., Oey, M. S., Amorín, R. O., Borthakur, S., Haye, M., Heckman, T., Ji, Z., Komarova, L., Reste, A. L., Leclercq, F., Marques-Chaves, R., . . . Xu, X. (2026). Lyman continuum escape during the onset of galactic winds in compact starbursts. Nature Astronomy.
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Hubble Space Telescope