The hands of the cosmic clock that measures the birth of the first galaxies must be moved further back. In fact, the oldest galaxy so far has been discovered, born immediately after the Big Bang, the origin of the Universe. Thanks to the data provided by the James Webb Space Telescope (Jwsst), an international team involving the Scuola Normale Superiore of Pisa, the University of Arizona, the University of Cambridge, Harvard & Smithsonian University and 20 other institutes and universities international, has precisely measured the distance between us and this cluster of stars, the farthest known so far, at over 13.4 billion light years.
Not only that: the experiment demonstrates that when the Universe was ‘only’ 300 million years old, 2% of its current age, fully developed star systems existed, much faster than models predicted. A discovery that contrasts with the predictions of the last decade, which considered the size, brightness and richness of stars in galaxies to be possible only in later phases.
The study, published on the physics and astronomy study platform ArXiv and in which NASA collaborated, is led by the researcher Stefano Carniani of the Cosmology and Astrophysics group of the Scuola Normale di Pisa, and also saw the participation of the doctoral student Eleonora Parlanti and the research fellow Giacomo Venturi.
The galaxy, ‘christened’ JADES-GS-z14-0 (the research program is in fact called Jwst Advanced Deep Extragalactic Survey) was present in the phase of life of the Universe called ‘cosmic dawn’ by astrophysicists, characterized by the formation of the first systems of stars and consequent generation of the first photons, gas and black holes. And at this time altitude the intrinsic properties of the galaxy are surprising. For example, JADES-GS-z14-0 is very bright and has already formed about a billion stars similar to our Sun. Until now, theoretical simulations assumed that the cosmic dawn was populated only by small, dim galaxies.
“The images obtained with the Webb telescope show us a snapshot of the Universe billions of years ago – explains Carniani -. Just as the rumble of thunder reaches our ears a few seconds later than when we observe the lightning discharge, the same happens with the light coming from distant galaxies, which gives us an image of the past. From this perspective, JADES-GS-z14-0 represents tangible proof that in the primordial Universe there were already fully developed luminous galaxies mysterious time, to think that such large groupings of stars were already present just 300 million years after the Big Bang.”
On a comparative level, the analysis of the data – obtained thanks to the NIRSpec spectrograph on board the Webb – revealed that, despite having a size over 10 times smaller than that of our galaxy, the Milky Way, JADES-GS-z14-0 is forming new stars at a rate 20 times faster. Furthermore, the light emitted is not due to a growing massive black hole as some theoretical models hypothesized, but to the photons that come from new stars, which are forming every year.
“The new data acquired through Webb – concludes Carniani – continue to confirm that the primordial Universe was already well developed with star formations similar to the more recent ones. The further step is to go even further, observing the Universe in its phases even closer to the Big Bang. In the meantime we should start working on the development of new theories that can explain the formation and evolution of these systems at the dawn of the cosmos.”
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