The Most Metal-Poor Star Ever Discovered Hints at Universe's First Supernovae

The elemental abundance of the most iron-poor star can be explained by an explosive event: a supernova. Now, scientists have taken a closer look at these supernovae and have found that the presence of massive stars in our early universe has major implications on the theory of star formation in the absence of heavy elements.

When the universe first began, only light elements such as hydrogen and helium existed. As the very first stars ended their short lives, the universe became enriched with heavy elements, which are essential building blocks for planets like our own Earth. This means that iron-poor stars are far older than the sun and can tell astronomers quite a bit about the first generation of stars.

In this case, the scientists found the most iron-poor star to date in early 2014. Called SMS J0313-6708, this iron-poor star has iron that's about a ten-millionth of that of our own sun. This means that it can be used to learn a bit more about the iron-poor stars in our early universe.

In order to learn a bit more about this star, the researchers focused on its very large carbon enhancement relative to iron and calcium. Previous studies suggested that this feature was consistent with a supernova in which the synthesized elements fall back. Yet the scientists wanted to see whether this scenario could also explain the extreme abundance pattern in the most iron-poor star.

The researchers compared observed abundances with theoretical calculations of the elements ejected by the supernova of first stars. In the end, they found that the abundance pattern can be reproduced if stars undergo a special type of supernova in which most of the ejected matter falls back to the central remnant. In the end, the model created successfully explained the low abundance of calcium, the non-detection of iron and the high abundance of carbon seen in SMS J0313-6708.

"If such supernovae are actually possible, the result supports the theoretical prediction that the first stars could be typical massive stars rather than monster-like objects with masses more than several hundred times that of the sun," said Ken'ichi Nomoto, one of the researchers, in a news release.

The findings are published in The Astrophysical Journal.