"James Webb" looks back in time: galaxy found with almost no heavy elements

A group of astronomers, using the James Webb Space Telescope (JWST), discovered a galaxy, called AMORE6, virtually devoid of heavy chemical elements. 

It is noted, that its existence convincingly proves the key predictions of the Big Bang theory. It is believed, that the Big Bang was the beginning of our Universe, which has been rapidly expanding since then and until now.

A process, called Big Bang nucleosynthesis, produced the first lightest elements: hydrogen, helium, and trace amounts of lithium. The heavier elements, which astrophysicists call metals, were formed much later in the interior of stars, that existed in the first epoch after the Big Bang.

The first generation of stars, known as the stellar population III, were the first to form heavy elements through nucleosynthesis in the interior. These stars did not contain heavy elements at all or contained them in extremely small amounts. Since stars are born in galaxies, not in isolation, there must have been population III galaxies — stars that did not contain metals at all.

Presence of galaxies with stars population III remained one of the issues of great interest to astrophysicists. The theory suggests, that some early galaxies, observed at large redshifts, should have zero metallicity. Confirmation of their existence would have a decisive impact on our current cosmological model.

With the help of JWST, astronomers have already discovered massive, well-developed galaxies, that appeared much earlier, than predicted by previous simulations. Until now, scientists believed, that such large and advanced galaxies should not have appeared so soon after the Big Bang. This made astronomers reconsider the idea that how fast galaxies developed and evolved.

However, even JWST, despite its leading capabilities, could not unambiguously identify a galaxy with zero metallicity. Although astronomers used the James Webb to observe galaxies, that formed several hundred million years after the Big Bang, none of them had a complete absence of heavy elements.

Oxygen plays a key role in the search for such galaxies. According to cosmological models, the first galaxies should have consisted only of hydrogen and helium, and not contained oxygen and other heavy elements. Astronomers use the emission line of doubly ionized oxygen, which is denoted in spectroscopy as O III. This line demonstrates the ongoing process of star formation, and is especially effective in the study of very distant systems with a significant redshift. 

In simpler galaxies, strong radiation O III may indicate an extremely low abundance of heavy elements. At the same time, weaker O III signals indicate, that galaxies formed under conditions, that differ from the current ones. Until recently, there were no convincing examples of this. A new study, led by researcher Infrared Data Processing and Analysis Center (IPAC) of the California Institute of Technology by Takahiro Morishita, indicates the possible discovery of one of the earliest galaxies, without heavy elements.

Meanwhile Morishita and his colleagues have likely found such a galaxy. It was detected with a redshift of 5.725. This means, that the light from it was emitted when the Universe was only about 900 million or 1 billion years old. The galaxy was discovered through gravitational lensing. “James Webb” discovered Hβ — emission, which describes the spectral lines of atomic hydrogen emission. However, no oxygen was detected. 

The galaxy was also found to have a low stellar mass and an extremely compact morphology. The fact, is that this galaxy is not as old as some of the fully formed galaxies, discovered by JWST before. It is some, what puzzling that this prime example of a pristine low-metallicity star formation environment was discovered almost a billion years after the Big Bang.