2023-06-14 14:29:32
The first stars of the Universe. Astronomers have been looking for them for decades. And they might finally have gotten their hands on some of them. Thanks to the James-Webb Space Telescope!
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The first stars of the Universe. THE astronomersastronomers call them stars of population IIIpopulation III. Stars that the theory describes as extremely massive and luminous, composed exclusively ofhydrogenhydrogen and helium. They would have appeared in the very beginnings of our UniverseUniverse. All beginnings on a cosmological scale, of course. That is some 400 million years only after the Big BangBig Bang. But so far, none of them had yet been observed.
So far. And still for some time no doubt. Even though a few days ago, Chinese Academy of Sciences researchers presented a star not quite like the others that they flushed out in the halo of our Milky WayMilky Way. A population star II. But which seems to have emerged more than 13 billion years ago. It could thus have formed after the supernova explosion of a population III star.
And now, two new studies — not yet peer-reviewed — suggest astronomers may be closer than ever to actually identifying some of these Population III stars. The first, made by Cambridge University researchers (UK) points to what may well look like a cluster of these primitive stars lurking on the outskirts of a galaxygalaxy distant. The second, conducted atItalian National Astrophysical Institutefeatures a tiny galaxy that may be composed of population III stars.
If these primitive stars have so long remained out of the reach of researchers, it is because the massemasse enormous — hundreds or even thousands of times more than our Sun — that they had to reach condemned them to a durationduration very short life. Always on a cosmological scale. Of the order of a few million years only. And astronomers had never even succeeded in detecting the traces of helium that only these stars with very high temperatures — of the order of 10 times that of our SoleilSoleil — seem to be able to leave behind.
Signs of population III stars
In 2017, a first hope in the mattermatter, in a galaxy called CR7, had been showered. And a few months ago, the hunt had experienced a resurgence of interest thanks to data returned by the télescope spatial James-Webbtélescope spatial James-Webb (JWST). But the detailed analysis that followed was inconclusive.
Yet astronomers continued to believe in the JWST’s ability to finally find population III stars. The team from the University of Cambridge chose to turn the instrument towards a galaxy discovered in 2015 by the Hubble Space Telescope, the galaxy GN-z11. A galaxy that dates back precisely to some 400 million years after the Big Bang. Spectroscopic analysis of the edges of GN-z11 confirmed the low metallicitymetallicity of the region and revealed suspicious traces of helium. Two elements which could constitute the proof of the existence, around GN-z11, of small groups of stars of population III. Stars each at least 500 times more massive than our Sun for a total of 600,000 times the solar mass. At this point, however, the scientists cannot rule out that the signal they have detected actually comes from a type of black hole that has also never been observed before. A kind of black holeblack hole that the theory presents as the beginnings of today’s supermassive black holes!
Researchers at the National Institute ofastrophysicsastrophysics Italian, they have detected what looks like a issueissue hydrogen andoxygenoxygen from a galaxy as small as it is far away. A detection that suggests the presence of two very small clusters of stars in a Universe only 800 million years after the Big Bang. And which could therefore well hide stars of population III.
Further analyzes will probably be necessary to confirm one and/or the other of these findings. And soon, the James-Webb Space Telescope will be looking at other population III star candidates. With the hope, for astronomers, of finally verifying their theories and understanding a little better how it all started.
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