Hydrogen bubbles from the primordial universe confirm the era of reionization

Using the infrared device called NEWFIRM on the four-meter Mayall telescope located in the Kitt Peak National Observatory of Infrared Astronomy Research (OIR Lab), a team of researchers discovered a group of galaxies, called EGS77, which contains what can be considered the first generation of stars that formed in the universe.

The researchers identified some overlapping bubbles of hydrogen gas ionized in primordial galaxies formed only 680 million years after the big bang. The light from the galaxies can in fact ionize the surrounding hydrogen gas and this causes the formation of bubbles which in turn allow the light from the galaxies to travel towards us without the attenuation that the hydrogen gas alone, without bubbles, would have caused.

This discovery represents the first direct evidence of a period, called the “reionization era”, during which the first generation of stars began to reionize the hydrogen gas that permeated the universe allowing the same light to begin to be visible through the “fog” of gas. The reionization put an end to the so-called “dark age” of the primordial universe.

This period, which began more or less half a million years after the big bang, ended with the formation of the first stars. The same period was deduced only through computer simulations and there was no direct evidence, at least until this study.

The group of primordial galaxies identified by the researchers corresponds to a thin strip of sky about one finger wide held at arm’s length. Within this strip would be at least 50,000 galaxies.
“The young universe was full of hydrogen atoms, which attenuated the ultraviolet light so much that it blocked our view of the first galaxies,” James Rhoads reported at a press conference representing research findings. “EGS77 is the first group of galaxies captured in the act of eliminating this cosmic fog.”

The study would confirm, therefore, the existence of a sort of “conical dawn,” which marks the boundary between a neutral and an ionized universe, something that had been predicted by the computer. The study is currently under review and should be close to publication.