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22.11.2023 13:41, Gennady Detinich
An in-depth analysis of light from a galaxy that existed back in the dawn of the universe, revealed the highest level of metals for that moment. Scientists cannot yet unambiguously indicate the source of the heavy elements they observe. With a high probability, these may turn out to be elusive “primary” stars, which makes the discovery one of the most important in astrophysics.
Galaxy GLASS-z13 is the oldest galaxy we have ever observed. Image source: JWST/James O’Donoghue
Science believes that almost all metals were born and can only be born in stars. Supernova explosions scatter them further and further. All of us and the Earth, as well as everything living and nonliving on it, were once atoms born in stars. Let us clarify that astrophysics considers everything heavier than hydrogen and helium to be metals.
The Big Bang produced mostly hydrogen. There was substantially less helium, even less lithium, and perhaps a vanishingly small amount of beryllium. Thus, the metallicity of the Universe increased gradually and quite predictably, which made it possible to imagine the evolution of stars, galaxies and everything else. But the observations of the early Universe, which were made possible by the James Webb telescope, are beginning to cast doubt on our understanding of the processes in it.
The discovery of a rather impressive amount of carbon in a young (or relatively ancient) galaxy around 350 million years after the Big Bang was one such discovery. Too many metals have been discovered in a galaxy with a redshift of z12.5, and carbon, let us remind you, is a metal for astrophysicists. James Webb conducted spectroscopy of the object for 65 hours, which was an unprecedented case. For such an instrument, spending so much time analyzing the spectrum from one galaxy is a luxury that few people can afford.
Analysis of the spectrum and the breadth of carbon present in the galaxy’s light suggested that carbon was present in stars rather than in interstellar or intergalactic gas. It is not possible to see the stars themselves at such a distance. If we are lucky, such stars can be distinguished in the event of gravitational lensing. In the meantime, thanks to Webb, we can conclude that in the ancient galaxy the stars were not at all pristine. In such galaxies it was expected to meet Population III stars, which should not contain metals. This is the first generation of stars after the Big Bang that are known only hypothetically.
According to the scientists’ findings, the source of carbon in the ancient galaxy is most likely Population III stars. Another source of carbon in the observed galaxy could be a supermassive black hole. The absorption of matter by a hole can be accompanied by the formation of metals. But this probability seems less. Finally, metals other than supernovae can be synthesized and ejected into space by AGB stars (asymptotic giant branch). However, for this to happen, the AGB stars would have to evolve significantly longer than in the observed case.
In general, “James Webb” gave scientists another riddle or answer, which should prompt a better understanding of the evolution of stars, galaxies and the Universe.
