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International researchers reveal origin of one of the oldest stars in the Milky Way galaxy

An international team of researchers, including scientists from the Canarian Astrophysics Institute (IAC), have confirmed the primeval origin of an ancient star in the Milky Way thanks to the 'ESPRESSO' device.

Stars with a lower metallic content are considered to be the oldest stars in the Milky Way, formed only a few hundred million years after the Big Bang. A time that is considered fleeting compared to the age of the Universe. These stars are true living fossils, with the early stages of the Universe’s evolution encoded in their chemical composition.

SMSS1605-1443 was discovered in 2018 and identified as one of the oldest stars in the galaxy based on its chemical composition, but its true nature was unknown. Now, thanks to the combined efforts of several European research groups and the use of the ESPRESSO spectrograph, the origin of this gem of stellar archaeology has been identified. The results of this research were published on 10 January in the journal Astronomy & Astrophysics (A&A).

This type of star is thought to have formed from the processed material inside the first massive stars, ejected in supernova explosions in the early stages of the formation of the Milky Way. As a result, these stars have a low iron content but a high carbon content, generated in the interior of the first massive stars. The high resolution of the ESPRESSO instrument has made it possible to analyse the relative carbon isotope composition in detail, which yields new information about the origin of this object.

“This discovery should be understood in the context of a project that started a decade ago, in which we have studied in detail all known stars of this rare class until we came across this marvellous finding, which helps us to better understand the chemical evolution of the Universe,” says Carlos Allende Prieto, IAC researcher and co-author of this work.

Rafael Rebolo, director of the IAC and another of the co-authors of this work, points out that “the multidisciplinary team formed by researchers from Spain, Italy, France, Portugal and Switzerland has shown that the ESPRESSO spectrograph is one of the best and most modern instruments for studying the formation of the most ancient stars”, adding that “the IAC is very proud to have participated in its construction”.

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