The James Webb Telescope observes the most distant galaxies in the universe

The James Webb Space Telescope has discovered the most distant galaxy that formed in the early universe, 320 million years after the Big Bang, according to research published Tuesday.

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Galaxies are difficult to detect because they are so distant and so young that their light signal is weak. The first observations by the James Webb Telescope (JWST), in service since July 2022, have identified several “candidate” galaxies in the infrared, a wavelength that is invisible to the human eye and allows its observation at long distances. .

The powerful infrared vision of its NIRCam imager, combined with observations in spectroscopy, which analyzes an object’s light to determine its chemical composition, “unequivocally” confirmed the presence of four galaxies. All are located towards the red end of the spectrum, and therefore far away.

Their age: Between 300 and 500 million years after the Big Bang (which occurred 13.8 billion years ago), two studies published in the journal Nature Astronomy describe. The universe was only 2% of its current age when it was in its so-called reionization period: after a period known as the Dark Ages, it reigned as a kind and began to form abundant stars.

Among the galaxies ejected by JWST, named JADES-GS-z13-0, would have formed “320 million years after the Big Bang” and its light is the most distant ever observed by astronomers, Stephen explained to AFP. Charlotte, from the Astrophysical Institute of Paris, is one of the authors of the study.

The space telescope confirmed the presence of the galaxy GM-z11, which it dated to 450 million years after the Big Bang, and the Hubble telescope detected its presence.

The four observed galaxies are much smaller in mass—a hundred million solar masses, compared to, for example, 1,500 billion for the Milky Way. But these galaxies are “very active in star formation, proportional to their mass”, the astrophysicist explained.

This CNRS researcher comments that the formation of stars will be done “at the same rate as the Milky Way”, which is “surprising at the very beginning of the universe”. Another lesson is that these galaxies are “extremely metal-free,” a finding consistent with the standard model of cosmology: the closer we get to the origin, the less time stars have had to make these complex molecules.

The JWST observation is “a technological tour de force,” hails Peter van Tock, an astronomer at the American Yale University, in a commentary attached to the study. The telescope is pushing back “the frontiers of exploration every month,” always going further into the universe, he underscores.

Last February, a NASA-built instrument observed a population of six galaxies between 500 and 700 million years after the Big Bang that appears to be much larger than expected. If the existence of these galaxies is confirmed by spectroscopy, it may call into question part of the theory of the formation of the universe.

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