Discovery of Ancient Star PicII-503 Sheds Light on Early Universe's Chemical Evolution

Astronomers have identified PicII-503, a second-generation star located in the ultra-faint dwarf galaxy Pictor II, approximately 150,000 light-years from Earth. This star exhibits the lowest iron abundance ever detected outside the Milky Way, containing only 1/40,000th the iron found in the Sun. Despite its iron deficiency, PicII-503 displays a significant overabundance of carbon, with a carbon-to-iron ratio over 1,500 times greater than that of the Sun.

The discovery supports the hypothesis that early supernova explosions were relatively low in energy, allowing lighter elements like carbon to be expelled into space while heavier elements such as iron remained. This process may explain the widespread presence of carbon in the universe, a crucial element for life.

Chris Davis, National Science Foundation Program Director for NOIRLab, commented on the significance of the find: "Discoveries like this are cosmic archaeology, uncovering rare stellar fossils that preserve the fingerprints of the universe's first stars."

The research, led by Anirudh Chiti of Stanford University, was published in the journal Nature Astronomy on March 16, 2026.