Modeling the Formation of Carbon-12

We can’t look inside an old red giant star to see what happens inside. Nor can we send a probe into a stellar collision. No spacecraft can go through a stellar explosion to witness elemental creation in those events. So, how do we know that this process is the correct one to explain the creation of carbon-12? As is often the case in astrophysics, researchers turn to computer models. Scientists at Iowa State University and the University of Tokyo created a complex supercomputer model of how alpha particles (the helium-4 atoms) and the 8Be nuclei combine to form much heavier atoms. In their model, this reaction created an unstable, excited carbon-12 state called a Hoyle state. (Named for astrophysicist Fred Hoyle who predicted this state in 1953.)

First, the researchers created a robust simulation of the environment and processes responsible for creating carbon-12 inside stars. Then, they ran it on the Fugaku supercomputer at the RIKEN Center for Computational Science in Kobe, Japan. The team also developed new techniques in computational artificial intelligence that would reveal alpha clustering in the Hoyle state implicated in the creation of carbon-12.

“There’s a lot of sublety—a lot of beautiful interactions going on in there,” said James Vary of Iowa State University. He is the first author of the resulting research paper. The research team points that alpha-particle clustering “is a very beautiful and fascinating idea and is indeed plausible because the (alpha) particle is particularly stable with a large binding energy.”

Ideas to Pursue in the Future

Now that the basic question of carbon-12 production seems to be answered by the simulations, Vary raises other questions about it. “Was carbon production mostly the result of internal processes in stars?” he asked. Or, could it also be in supernova explosions? Could it happen in the collisions of neutron stars? Recent studies show that such mergers create gold and platinum. So, were conditions ripe for carbon-12 to come about?

There are still many details to be worked out before researchers have a complete understanding of the carbon-12 process. But, understanding the role of nucleosynthesis is a prime goal. “his nucleosynthesis in extreme environments produces a lot of stuff,” Vary said, “including carbon.”