Oldest Carbon-rich Stars Open a Window to Early Cosmic Chemistry

Oldest Carbon-rich Stars Open a Window to Early Cosmic Chemistry By Carolyn Collins Petersen - March 30, 2026 11:10 PM UTC | Stars Astronomers studying the ultra-faint dwarf galaxy Pictor II have found an extremely chemically peculiar star that contains traces of elements created by the first stars in the Universe. It's called PicII-503, a "second-generation star" that is one of the most chemically primitive stars ever found. It's extremely low in iron but is enhanced with carbon. Its home galaxy, Pictor II, is a satellite of the Large Magellanic Cloud (itself a satellite of the Milky Way Galaxy), and lies some 150,000 light-years away. Its stars may play a role in helping us understand chemical evolution in early epochs of cosmic time. Chemically enriched metal poor stars such as PicII-503 aren't limited to just one area of space. Astronomers have found them in the Milky Way's halo and have long worked to explain their existence. The fact that this star lives in a galactic "fossil graveyard" makes Pictor II good place to study other similar stars. What astronomers find there will contribute to an increased understanding of the chemical evolution of the earliest generations of stars. The galaxy's few thousand stars are more than 10 billion years old and began forming relatively early in the history of the Universe. It stopped forming stars billions of years ago and this entire whole dwarf galaxy is dominated by dark matter, *A chart showing the chemical composition of the first stars compared to the composition of the Sun. PicII-503 would show hydrogen and an enriched amount of carbon (among other elements). Courtesy NASA/ESA/STScI* Understanding Ancient Stars PicII-503 and stars like it act as stellar time capsules. That's because they contain their original primordial hydrogen and helium (first created in the Big Bang), but they have really low amounts of heavy elements. To astronomers, "heavy" elements or "metals" are those cooked up inside stars (such as carbon,...