Decoding the Carbon Abundance in the Universe's Oldest Stars

An image captured by the Dark Energy Camera (DECam) mounted on the Víctor M. Blanco 4-meter Telescope in Chile depicts a field of stars within the dwarf galaxy Pictor II, which is more than 10 billion years old.

Contained within this image is the star PicII-503, classified as a Population II, or second-generation, star. This classification indicates it is among the oldest stars in the universe.

Unveiling an Ancient Star

Population II stars originated when the cosmos was young, prior to the significant fusion of heavier elements. Consequently, they are primarily composed of hydrogen and helium. PicII-503, for instance, possesses approximately 1-40,000th of the iron found in the Sun, a composition typical for such an ancient star.

An Unexpected Carbon Richness

However, researchers reported a surprising finding: PicII-503 is unusually rich in carbon. Its carbon-to-iron ratio is over 1,500 times greater than that of the Sun, a characteristic also observed in numerous other Population II stars.

Researchers reported that PicII-503 is unusually rich in carbon. Its carbon-to-iron ratio is over 1,500 times greater than that of the Sun.

Supernova's Role in Cosmic Carbon

Astronomers have advanced several theories to account for this unique composition. As PicII-503 remains within its primordial dwarf galaxy, its composition was utilized to test these hypotheses.

The star's high carbon content supports a theory suggesting that during a supernova explosion, lightweight carbon from a star's outer shell is ejected farther than other elements. This process may also explain carbon's widespread presence in the universe, where it serves as a foundational building block for life.