This discovery shakes up the certainties of modern astronomy. A team of researchers believes they have discovered the purest star in the universe: it was formed from gas from a population III star – these extremely massive and luminous stars, almost entirely composed of hydrogen and helium, formed in the very early days after the Big Bang.
According to NASA, these primitive stars could reach temperatures close to 100,000 degrees, or 90,000 hotter than the Sun. At such levels, physics changes scale: the higher the temperature, the more electromagnetic radiation intensifies, and therefore light too. Population III stars, much brighter than the daytime star, mainly emitted ultraviolet rays.
In the new study published in Nature Astronomy, scientists argue that the first stars formed from virgin gas, which made them more massive and prevented them from surviving until today. “If their descendants were light enough, they could still exist and would be recognizable by their very low metallicity. (the proportion of elements heavier than helium and hydrogen in their composition, editor’s note)»they write.
SDSS J0715-7334 enters research
Until now, the record for metal poverty was held by a star nestled in the thick disk of the Milky Way. By combing through data from the Sloan Digital Sky Survey-V, a large celestial mapping program, the team led by Alexander Ji of the University of Chicago identified several constellations abnormally devoid of heavy metals. Thanks to the Magellan telescopes, scientists have discovered this extraordinary red giant, potentially the purest ever observed. They named it SDSS J0715-7334.
“All the heavier elements in the universe were produced by stellar processes, such as fusion reactions linked to supernova explosions or collisions between very dense stars”specifies Alexander Ji in a press release. In this context, a star so poor in metals is an exception. In addition, SDSS J0715-7334 is very weakly enriched in carbon, unlike similar stars, underlines IFL Science.
The team hypothesizes that this red giant was formed from gas coming from a population III star, which would explain its almost pure character. By tracing its origin, they concluded that it came from the Large Magellanic Cloud, a satellite galaxy of the Milky Way – in other words our neighbor on a cosmic scale.
But be careful. Researchers are already tempering enthusiasm. If the James Webb space telescope, launched at the end of 2021, has opened the way to a wave of galactic discoveries, in particular of metal-poor stars, uncertainties remain significant. The margin of error on the metallicity of SDSS J0715-7334 does not yet allow us to affirm that it is a true descendant of the first stars. There remains a fascinating possibility: Alexander Ji’s team may have glimpsed one of the last vestiges of the very first lights of the universe.
