Astronomers Identify Most Pristine Star in Milky Way

Astronomers have identified SDSS J07157334, the most chemically pristine star known, a dim red giant that formed in the early universe and now resides in the Milky Way galaxy about 80,000 light-years from Earth. The find, led by Alexander Ji, an assistant professor of astronomy and astrophysics at the University of Chicago, provides a rare snapshot of cosmic evolution shortly after the Big Bang.

The star's exceptional purity stems from its extremely low levels of heavy elements, or "metals" as astronomers term them, including iron and carbon. Analysis shows it contains less than 0.005 times the metal content of the Sun, making it twice as metal-poor as the previous record holder and 40 times more deficient in iron than the most iron-poor star previously observed. Its composition suggests it formed from gas influenced by just one early supernova, likely as part of the second generation of stars born a few billion years after the universe's origin 13.7 billion years ago.

The discovery emerged from data in the Sloan Digital Sky Survey V, a comprehensive sky-mapping project that scans millions of spectra to spot anomalies. Ji's team, which included several University of Chicago...