Free Astronomy Magazine May-June 2026

38 MAY-JUNE 2026 ASTRO PUBLISHING lighter elements that are near the star’s outer regions, like car- bon, are ejected into the inter- stellar medium to seed the for- mation of the next generation of stars. PicII-503 supports the low-energy supernovae explana- tion because it is found in one of the smallest dwarf galaxies that we know of. If the supernova that produced the metals found in PicII-503 was high-energy, then the elements would have escaped the gravita- tional pull of the small Pictor II dwarf galaxy. PicII-503 also demonstrates that the carbon- enhanced metal-poor stars ob- served in the Milky Way halo likely originated from ancient relic dwarf galaxies that have, over time, merged with ours. “What excites me the most is that we have observed an out- come of the very initial element production in a primordial gal- axy, which is a fundamental ob- servation!” says Chiti. “It also cleanly connects to the signature that we have seen in the lowest-metallic- ity Milky Way halo stars, tying to- gether their origins and the first-star- enriched nature of these objects.” “Discoveries like this are cosmic ar- chaeology, uncovering rare stellar fossils that preserve the fingerprints of the Universe’s first stars ,” says Chris Davis, NSF Program Director for NOIRLab. “We look forward to many more discoveries with the start of the NSF–DOE Rubin Observatory’s Legacy Survey of Space and Time later this year.” PicII-503 offers a rare, direct glimpse into the Universe’s first chapter of chemical evolution, which is a foun- dational moment that ultimately set the stage for planets, chemistry, and life itself. It also connects long- standing mysteries about ancient stars in the Milky Way to their ori- gins in primordial dwarf galaxies. T he Dark Energy Camera (DECam), fabricated by the Department of Energy (DOE), is mounted on the Víctor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-Ameri- can Observatory (CTIO) in north-central Chile. [CTIO/NOIRLab/DOE/NSF/AURA/R. Hahn (Fermi National Accelerator Laboratory)] candidate, allowing researchers to target it for detailed follow-up study. “Without data from MAGIC, it would have been impossible to isolate this star among the hun- dreds of other stars in the vicinity of the Pictor II ultra-faint dwarf gal- axy,” says Chiti. By combining data from MAGIC, the Magellan/Baade Telescope, and ESO’s Very Large Telescope, the team found that PicII-503 has the lowest iron and calcium abundances ever measured outside of the Milky Way. This paucity of iron and cal- cium makes it the first object that clearly preserves enrichment from the first stars in a relic dwarf galaxy. “Discovering a star that unambigu- ously preserves the heavy metals from the first stars was at the edge of what we thought possible, given the extreme rarity of these objects,” says Chiti. “With the lowest iron abundance ever derived in any ultra- faint dwarf galaxy, PicII-503 provides a window into initial element pro- duction within a primordial system that is unprecedented.” Even more remarkably, the team dis- covered that PicII-503 has a carbon- to-iron ratio that is over 1500 times that of the Sun. This overabundance matches the distinct carbon signa- ture of low-iron stars long observed in the Milky Way halo. These are known as carbon-enhanced metal- poor stars, and their origin has re- mained unknown until now. One hypothesis is that carbon-en- hanced metal-poor stars are second- generation stars that preserve the chemical elements produced by low- energy supernovae of first-genera- tion stars. During this process, heavy elements that form close to the star’s interior, like iron, fall back into the remnant compact object, while !