Astronomers using the James Webb Space Telescope (JWST) have made a groundbreaking discovery that could validate long-held assumptions about the early universe. The discovery, detailed in a recent study submitted to Nature, revolves around the detection of AMORE6, a galaxy that may be a rare example of what scientists have been searching for: a pristine, zero-metallicity galaxy. This galaxy, with a redshift of z = 5.725, shows no trace of elements heavier than hydrogen and helium—elements formed only after the Big Bang. The research supports the Big Bang model, providing crucial evidence that the first galaxies, formed by early stars, followed the expected patterns predicted by cosmologists.
This study, published on arXiv in July 2025, titled “Pristine Massive Star Formation Caught at the Break of Cosmic Dawn”, was led by Takahiro Morishita, a staff scientist at the California Institute of Technology’s Infrared Processing and Analysis Center (IPAC). In this article, we dive deeper into how AMORE6 fits the cosmological model and explore the implications of this discovery.
The Search for Population III Galaxies
Population III stars are theorized to be the first generation of stars formed after the Big Bang, composed solely of hydrogen, helium, and trace amounts of lithium—without the heavier elements created later in the stellar evolution process. These stars would have been the forges of all subsequent elements through the process of stellar nucleosynthesis. The galaxies that hosted these stars, known as Population III galaxies, should have no metals (elements heavier than helium).
“The existence of galaxies with no elements such as oxygen—formed by stars after Big Bang nucleosynthesis—is a key prediction of the cosmological model,” the researchers write. “However, no pristine ‘zero-metallicity’ Population III galaxies have been identified so far.” This lack of discovery had long remained a significant gap in our understanding of galaxy formation in the early universe.
The search for these zero-metallicity galaxies has been a challenge, as the early universe was expected to be dominated by hydrogen and helium. As such, any detection of a galaxy formed in these pristine conditions would be a monumental find. AMORE6, with its minimal metallicity, could be the key to confirming the existence of Population III galaxies and further validating the Big Bang theory.
AMORE6: A Surprising Discovery
The AMORE6 galaxy was discovered through gravitational lensing, which amplified the light from the distant galaxy, making it easier for astronomers to study. Observed at a redshift of z = 5.725, AMORE6’s light left the galaxy when the universe was just about 900 million to 1 billion years old. This time frame places it in a period that astronomers have long speculated would be home to the earliest star formations.
When analyzing the spectral data from AMORE6, the researchers found significant clues that suggest it may indeed be a pristine galaxy. The absence of oxygen in its emissions lines—specifically the OIII emission, which is crucial for determining metallicity—points to a very low-metallicity environment. “The absence of [O iii] immediately indicates that AMORE6 harbors a very low-metallicity, near pristine, interstellar medium,” the authors explain. This lack of oxygen is a defining characteristic of zero-metallicity galaxies, offering strong evidence that AMORE6 fits the model of early, untainted star formation.
Despite the galaxy’s pristine nature, AMORE6 also displays unexpected features. Its compact morphology and low stellar mass indicate that it may be part of a different evolutionary path than other large, mature galaxies found earlier by the JWST. While the galaxy is not as old as some previously discovered fully-formed galaxies, its lack of metals places it in a category unique to early universe studies.
Implications for the Big Bang Theory
The discovery of AMORE6 is not just a triumph in the search for Population III galaxies but a direct validation of the Big Bang model. For years, cosmologists have hypothesized that early galaxies formed under conditions vastly different from what we see today—conditions marked by an absence of heavy elements. The identification of a galaxy like AMORE6, with its ultra-low metallicity and primitive composition, directly supports the predictions made by the Big Bang nucleosynthesis model.
“The finding of such an example at a relatively late time in cosmic history is surprising,” the researchers write. “However, regardless of cosmic epoch, the identification of a potentially pristine object is a key validation of the Big Bang model.” The discovery not only fills a gap in the timeline of galaxy formation but also strengthens the foundation of cosmological theory, particularly in understanding how the universe transitioned from a mostly hydrogen-helium mixture to the complex, metal-rich systems we observe today.
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