Astronomers find one of the oldest stars ever, preserving clues from the early universe

After the Big Bang, the universe contained almost only hydrogen and helium. There were no heavy elements, and the early universe had no trace of metals. The first stars were formed a few hundred million years later, and nuclear fusion inside their cores produced the first heavy elements, such as carbon, magnesium, and oxygen. When these stars died, the supernova explosion blasted these elements into space. These elements mixed with the gas clouds and created ingredients for the next generation of stars.

Stars that formed early in cosmic history had very low metallicity and acted as time capsules. PicII-503 is a star found in the dwarf galaxy Pictor II. The surprising thing about this star is that it contains almost no iron and an extremely high carbon abundance. This makes it one of the most chemically primitive stars ever found. 

This type of star, called a carbon-enhanced metal-poor (CEMP) star, was identified using the Dark Energy Camera mounted on the Victor M. Blanco Telescope. 

Scientists think the first star that enriched the gas that formed the star underwent a low-energy supernova which caused the heavier elements to fall back into the collapsed remnant, leaving only the lighter elements to escape. The gas then formed a second-generation star. PicII-503 gives a direct chemical record of the first stars, increasing our understanding of cosmic chemical evolution.