Peculiar galaxy seems to contain surprisingly pristine stars

A fascinating discovery has been made in the depths of space, unveiling a galaxy that seems to be thriving with ancient, primordial stars. This revelation could potentially offer astronomers a groundbreaking opportunity to observe a type of star that is believed to have originated shortly after the birth of the universe, a phenomenon that has eluded direct observation until now.

Despite the remarkable capabilities of the James Webb Space Telescope (JWST) in allowing us to glimpse back into the earliest stages of the cosmos, the search for evidence of the first stars, known as population III stars, has been a challenging quest. These massive celestial bodies, composed mostly of hydrogen, are theorized to have emerged in the nascent universe devoid of the heavier elements produced by the stellar life cycle.

While there have been tantalizing hints pointing towards the existence of population III stars, conclusive proof has been elusive due to the rapid contamination of galaxies with heavier elements shortly after the big bang, within a few hundred million years.

Now, a team led by Takahiro Morishita from the California Institute of Technology has uncovered a galaxy named AMORE6, located within the Abell2744 galaxy cluster, that is predominantly composed of hydrogen—an indication of population III stars. Surprisingly, this galaxy appears much later in cosmic history than anticipated for hosting such ancient stars, emerging approximately a billion years after the universe’s inception.

Through meticulous observations using the JWST, Morishita’s team detected a conspicuous absence of a common oxygen ion in the light emitted by AMORE6. This absence suggests that the galaxy contains no more than 0.2% of the oxygen present in our sun, implying a significant lack of heavier elements within AMORE6.

Given the advancing age of the universe, the existence of pristine galaxies like AMORE6 becomes increasingly rare. In the JWST images, AMORE6 appears to be relatively isolated, a factor that may account for its exceptional purity. Morishita speculates that the galaxy’s seclusion could have delayed the onset of star formation, leading to its pristine state. “That isolation means that this galaxy might be in an area that didn’t have enough gas to trigger star formation earlier. That means that this galaxy might be a late bloomer in one sense,” Morishita explains.

“If the results are confirmed, it’s really remarkable, because typically we don’t expect to find such pristine galaxy environments so late in the development of the universe,” remarks Fabio Pacucci from the Harvard-Smithsonian Center for Astrophysics in Massachusetts.

This discovery also holds implications for the potential observation of “direct collapse” black holes, which are theorized to form from massive clouds of pristine gas rather than through the conventional pathway of stellar collapse. While these enigmatic entities have been predicted by astronomers, their formation has remained elusive, partly due to the belief that pristine gas was only accessible within the first 100 million years after the big bang—an era too distant for current detection methods. However, if pristine gas can persist for longer periods, as indicated by AMORE6, the probability of observing a direct collapse black hole could be significantly enhanced, Pacucci suggests.

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