There was a time when there were no stars. Shortly after the Big Bang, in an endless sea of hydrogen and helium, the first stars began to appear due to the monstrous density of the gas. These stars were called Population III. No one has seen them yet, but new instruments, including the James Webb, give hope of finding such objects at the dawn of the Universe. Astronomers have recently come close, having discovered the best candidate to date among Population III stars.
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It is believed that the first stars in the Universe, or Population III stars, were very massive — much larger than today’s giant stars. And the larger the star, the faster it burns out and scatters its remains across space, managing to synthesize heavier elements in its depths than the original hydrogen and helium. This is why we do not see the first stars — their life was fleeting, but they left traces of their presence in the form of certain chemical elements.
A large international team of scientists led by Seiji Fujimoto of the University of Texas at Austin submitted a paper to The Astrophysical Journal, which they also posted on the free preprint site arXiv. In the paper, the researchers reported on a promising method for searching for the first stars and the discovery of the best candidate galaxy to date that likely contains Population III stars.
This galaxy, named GLIMPSE-16403, is not yet a proven host of Population III stars. However, the very existence of such a candidate suggests that it is only a matter of time before the first stars are discovered in the Universe.
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Fujimoto and his colleagues decided to speed up the search by focusing on smaller patches of the sky to look for chemical fingerprints of the first stars. The scientists zeroed in on galaxies with strong spectra of hydrogen and helium, but minimal amounts of other elements. They found two candidates. One was a dud, but the other, GLIMPSE-16403, which appeared about 825 million years after the Big Bang, met all the criteria for a Population III galaxy.
This discovery makes GLIMPSE-16403 the best candidate to find the stars that first lit up the Universe. Determining the nature of the stars in GLIMPSE-16403 will require further work, which could prove challenging: detailed spectral analysis is needed, and this is difficult to obtain over such a vast distance in spacetime. Nevertheless, this is an incredibly exciting discovery, and makes the discovery of Population III stars seem inevitable.