Free Astronomy Magazine May-June 2026

37 MAY-JUNE 2026 ASTRO PUBLISHING A stronomers have discovered one of the most chemically primitive stars ever identified — an ancient stellar relic that pre- serves the chemical imprint of the very first stars in the Universe. This star, named PicII-503, resides in the tiny, ultra-faint dwarf galaxy Pictor II. The discovery was enabled by the U.S. Department of Energy-fabri- cated Dark Energy Camera (DECam), mounted on the U.S. National Sci- ence Foundation Víctor M. Blanco 4- meter Telescope, at NSF Cerro Tololo Inter-American Observatory (CTIO) in Chile, a Program of NSF NOIRLab. Pictor II is located in the constella- tion Pictor. It contains several thou- sand stars and is more than ten billion years old. PicII-503 lies on the outskirts of the galaxy, and it con- tains less iron than any other star ever measured outside of the Milky Way, while also having an extreme overabundance of carbon. These sig- natures unmistakably match those of carbon-enhanced stars found in the outer reaches of the Milky Way, whose origins have, until now, been a mystery. The study was led by Anirudh Chiti, Brinson Prize Fellow at Stanford Uni- versity, and the results are presented in a paper appearing in Nature As- tronomy . The first stars in the Universe formed from gas that contained only the simple elements, hydrogen and he- lium. Within their fiery cores, this first generation of stars created the first elements heavier than helium, such as carbon and iron, which as- tronomers refer to as “metals.” When these stars exploded, they re- leased their heavy elements into the interstellar medium to be recycled into the next generation of stars. Second-generation stars are like time capsules, preserving the low amounts of heavy elements released during the explosive deaths of first- generation stars. By searching for these rare, low-metallicity stars and deriving their chemistry, scientists can better understand the mecha- nisms of initial element production in the Universe. PicII-503 is the first unambiguous ex- ample of a second-generation star in an ultra-faint dwarf galaxy. It was uncovered in data from the DECam MAGIC (Mapping the Ancient Gal- axy in CaHK) survey, a 54-night ob- serving program designed to iden- tify the oldest and most chemically primitive stars in the Milky Way and its dwarf galaxy companions. Using a specialized narrow-band filter sen- sitive to calcium absorption features, astronomers were able to estimate the metal content of thousands of stars from imaging data alone. Among the hundreds of stars near Pictor II, MAGIC data singled out Pic- II-503 as an exceptionally metal-poor T his image shows stars in the ultra-faint dwarf galaxy, Pictor II. It is a satellite galaxy of the Large Magellanic Cloud, which is a satellite galaxy of the Milky Way, and is located in the constellation Pictor. The system is made up of several thou- sand stars and is more than ten billion years old. Within this small, ancient galaxy, astronomers discovered a star, PicII-503, with the lowest iron content ever measured outside of the Milky Way. With less than 1/40,000 th the amount of iron as the Sun, PicII-503 is the clearest example of a star within a primordial system that preserves the chemical enrichment of the Uni- verse’s first stars. PicII-503 also has an extreme overabundance of carbon, providing the missing link to connect carbon-en- hanced stars observed in the Milky Way halo to an origin in ancient dwarf galaxies. [CTIO/NOIRLab/DOE/NSF/AURA. Image processing: Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani & D. de Martin (NSF NOIRLab). Acknowledgment: PI: Anirudh Chiti, Alex Drlica-Wagner]