Penn State scientists say dwarf galaxies were among earliest universe starlight

Feb. 28 (UPI) -- Penn State University researchers said in a study Wednesday that working with the James Webb Space Telescope they found the first full spectra of tiny galaxies, revealing some of the earliest starlight in the universe.

Scientists said it's the clearest picture yet of tiny galaxies created less than a billion years after the Big Bang. The study published in the journal Nature suggests these galaxies are central to the cosmic origin story.

"Something turned on that started pumping out very high energy photons into the intergalactic void," said Joel Leja, one of the authors of the study. "These sources worked like cosmic lighthouses that burned off the fog of neutral hydrogen. Whatever this was, it was so energetic and so persistent, that the entire universe became re-ionized."

The Penn State study demonstrated that small galaxies were strong candidates for that "something" that is believed to have sparked the re-ionization of the universe.

Leja, a Penn State assistant professor of astronomy and astrophysics, said normal matter in the universe began as hot dense fog consisting of mainly hydrogen and helium nuclei.

When it cooled and expanded, he said, protons and electrons bonded forming neutral hydrogen for the first time.

About 500 to 900 million years after the Big Bang, that hydrogen began separating into ionized gas, which he said lifted the primordial fog, letting light travel unimpeded through the universe.

"If the other low-mass galaxies in the universe are as common and energetic as these, we think we finally understand the lighthouses that burned off the cosmic fog," Leja said. "They were incredibly energetic stars in many, many tiny little galaxies."

According to scientists, what made this study possible was "the unique combination of JWST sensitivity and the gravitational lensing effect of the Abell 2744 cluster -- nearby galaxies that act like cosmic magnifiers, distorting space and amplifying the light of background galaxies."

That, in turn, made it possible to determine how abundant small galaxies were and what their ionizing properties were in the first billion years of the universe's existence.

"We found that small galaxies outnumbered massive galaxies by about a hundred to one during this epoch of re-ionization of the universe," study first-author Hakim Atek, astrophysicist at Sorbonne University, said in a statement.

The researchers say this study appears to confirm the hypothesis relating to low mass galaxies and it offers "the clearest evidence to date that low-mass galaxies played a central role in the re-ionization of the universe."

They now want to expand the study to a larger scale to confirm that what they analyzed is representative of the average distribution of galaxies in the universe.

The researchers said these study observations provide early star formation insight on how galaxies emerged from primordial gas and how they then evolved into the universe that's known today.

Their study is titled Most of the photons that re-ionized the Universe came from dwarf galaxies and was published Wednesday in the journal Nature.