Supernovae may have restrained the escape of ionizing radiation — Live Science
Supernova explosions may not have been the main factor that dispersed the hydrogen fog in the early Universe, but instead may have trapped ionizing ultraviolet radiation inside galaxies. This is indicated by the results of a study published on October 15, 2026, in the journal Nature Astronomy, Live Science reports.
How the Universe became more transparent
About 400,000 years after the Big Bang, the Universe cooled enough for atoms to form, mainly neutral hydrogen. This gas formed a cosmic fog opaque to ultraviolet light. Later, radiation from the first stars and galaxies ionized neutral hydrogen, splitting atoms into protons and electrons. This process is called the epoch of reionization.
Astronomers still do not have a complete answer as to which objects caused reionization and how it occurred. It was previously assumed that supernovae — the explosive deaths of massive stars — played an important role. They were expected to create powerful galactic winds that helped Lyman-continuum photons escape galaxies and ionize intergalactic gas.
Observations of six galaxies
The team used the Hubble Space Telescope to study six compact galaxies with active star formation, located about 3.5 billion light-years away. Their diameter usually does not exceed 6,500 light-years, while their star-formation rate is about 10 solar masses per year.
More current news is available on the UA.News Telegram channel Telegram.
Analysis of the spectra made it possible to determine the origin, chemical composition, speed and direction of stellar winds. During the first three million years of star formation, winds from young massive stars moved at nearly 3,000 kilometers per second and carved a path through neutral gas and dust. This enabled ionizing radiation to leave the galaxy.
The effect of supernovae
After about three million years, when the most massive stars began exploding as supernovae, the situation changed. Ejected matter was added to the gas and dust in galaxies, making the environment denser for Lyman-continuum photons. The oldest galaxies in the sample, where supernova-driven winds were the fastest, allowed the least ionizing radiation to pass through.
The authors note that this result does not agree with most cosmological simulations, in which the fraction of radiation escaping a galaxy is greatest after supernova-driven winds emerge. The researchers propose expanding the sample of galaxies and conducting higher-resolution observations in other wavelength ranges.
