July 23, 2014

Simulations Reveal More About Oldest Known Star

Tiffany Trader
astrophysics illustration

Thanks to the power of supercomputing, scientists from the Universities of Göttingen and Copenhagen now have a better understanding of one of the most ancient stars in the universe. The results of their study were published in the July 21st edition of Astrophysical Journal Letters.

The group used high-resolution computer simulations to model the formation of the oldest known star, which was discovered right in our Milky Way Galaxy. The star, which has the abbreviated name of SM0313, was born 13.6 billion years ago — just 100 or 200 million years after the Big Bang.

The astrophysicists performed cosmological simulations with a supercomputer from the North-German Supercomputing Alliance to uncover the dynamics of gas and dark matter as well as the chemical evolution. The thing that sets SMSS (SkyMapper Southern Survey) J031300.36−670839.3 apart is its chemical composition, which can be seen in its spectrum lines.

The scientists expect this simulation to shed light on the transition from the first to the second generation of stars in the universe. So-called first generation stars were formed out of a primordial gas comprised of hydrogen and helium. They were denser than our Sun having ten to five hundred times more mass. Nuclear processes deep inside these stars formed heavy elements like iron, silicon, carbon, and oxygen. These stars eventually perished in supernova explosions and the heavy elements that were ejected became second-generation stars. Stars with very few heavy elements indicate that not many stars contributed to that star’s birth. Such is the case with SM0313.

“Even for the oldest-known star in the Milky Way galaxy, our simulations indicate that the gas efficiently cools due to the presence of heavy elements,” says Dr. Stefano Bovino at the Institute for Astrophysics Göttingen, lead study author. Such conditions favor the formation of low-mass stars and suggest that the transition to the second generation resulted from a supernova explosion. “The heavy elements provide additional mechanisms for the gas to cool, and it is very important to follow their chemical evolution,” explains co-author Dr. Tommaso Grassi from the Center for Star and Planet Formation at the University of Copenhagen.

The new simulations were enabled by a chemistry package called KROME, through a joint effort led by the University of Copenhagen. A video of the computer simulations can be viewed at vimeo.com/101191120.