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Discovery of the most distant dwarf galaxy detected so far

An international team, including the Ikerbasque research professor of the University of the Basque Country (UPV/EHU) and associate of  Donostia International Physics Center (DIPC) Tom Broadhurst, used the high resolution of the James Webb Space Telescope (JWST) combined with a powerful gravitational lens to conclude that the galaxies that formed in the early universe were typically very small, indicating a hierarchical process of evolution from dwarf galaxies gradually merging together as a result of mutual gravity, until massive galaxies such as our Milky Way were formed. The study has just been published in the journal Science.

By analysing the spectra of several galaxies in the distant Universe, the team was also able to confirm the detection of the most distant dwarf galaxy found to date. As Broadhurst explains, “this tiny, very low luminosity galaxy is one of the first to form, only 500 million years after the Big Bang, when the volume of the Universe was about a thousand times smaller than it is today.”

Broadhurst is part of an international team with a large allocation of JWST time for the study of stars and galaxies in the distant universe through gravitational lensing, a method that uses massive objects, such as clusters of galaxies, to magnify in brightness and size the targets behind them. Earlier this year, the team had already measured the spectrum of several stars and galaxies using this technique, “and we were very excited when we detected this very high redshift galaxy.” The latest observations enabled the team to confirm that “the distance estimate of this galaxy is 100% reliable, because we were able to recognise distinctive elements in its spectrum, such as hydrogen, carbon, oxygen and neon, which come from its hot gas.”

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