In a scientific achievement that could transform humanity's understanding of the universe's origins, an international team of astronomers has succeeded in detecting one of the most elusive puzzles in the history of the early universe, after managing to discover the neutral gas that fuelled the birth of the first stars inside nascent galaxies — just 700 to 800 million years after the Big Bang.
This discovery is considered a pivotal step toward understanding how the first galaxies formed and grew during what is known as the "cosmic dawn" — the period that witnessed the launch of the earliest processes of building the cosmic structures we see today.
For many years, scientists were able to observe stars and hot ionised gases in distant galaxies, which allowed them to redraw important parts of cosmic history. Yet one of the most critical components of star formation remained out of reach: neutral gas, which constitutes the fundamental raw material from which stars are born.
Despite the scientific leaps achieved by modern space telescopes, detecting this type of gas directly had represented an enormous challenge, particularly in extremely distant galaxies dating back to the universe's beginnings.
Using the giant radio telescope array located in the Atacama Desert, researchers focused on 4 young galaxies experiencing intense star-forming activity.
The team managed to capture a rare signal emitted by neutral oxygen atoms — a signal considered one of the most precise tools available for tracing neutral gas inside galaxies. The significance of this observation lies in that it allows a direct view of the material that subsequently transforms into stars, going beyond the indirect indicators previously used, which had generated considerable scientific uncertainty.
To verify the results, scientists compared the detected signals with other signals associated with ionised gas, revealing that the greater part of the observed material was indeed the long-sought neutral gas.
The work did not stop at observation alone; the data were combined with recent observations from advanced space telescopes, enabling researchers to study the physical and chemical properties of the gas within these galaxies.
The findings revealed that those galaxies contained enormous quantities of dense gas, at levels rivalling the most active star-producing galaxies of the modern era — indicating that the early universe harboured highly efficient "star factories" operating at an astonishing pace.
The study also showed that the environmental conditions inside those galaxies differ from their present-day counterparts, granting scientists a deeper understanding of how galaxies evolved over billions of years.
This achievement is classified as the most distant direct detection of neutral gas ever accomplished in normal star-forming galaxies.
Lead co-investigator Professor Yoshinobu Fudamoto said the findings represent an important turning point in early-universe research, because they not only provide new data but also give scientists the ability to reanalyse a vast archive of previous observations with greater precision and clarity.
He added that this new technique will allow for a better understanding of the stages of formation of the first galaxies and how they evolved during the era that immediately followed the birth of the universe.
Scientists believe this discovery does not concern just 4 galaxies, but rather opens the door to studying thousands of distant galaxies dating back to the earliest epochs of the universe.
With the unveiling of the "missing cosmic fuel" that powered the birth of the first stars, researchers are now closer to answering one of science's greatest questions: how did the dark primordial universe transform into a world filled with galaxies, stars, and planets?
In doing so, this achievement adds a new and significant piece to the puzzle of cosmic history, bringing humanity one further step closer to understanding the story of the universe's origins from its very first moments.