With the help of the world’s most powerful supercomputer and new artificial intelligence techniques, an international team of scientists has theorized how extreme conditions in stars produce carbon-12, which they describe as “a gateway criticism towards the birth of life”.
The fundamental question of the researchers was: “How does the cosmos produce carbon-12?” said James Vary, professor of physics and astronomy at Iowa State University and a longtime member of the research collaboration.
“It turns out that it’s not easy to produce carbon-12,” Vary said.
It takes the extreme heat and pressures inside stars or during stellar collisions and explosions to create emergent, unstable, excited carbon nuclei with three weakly bound clusters, each with two protons and two neutrons. A fraction of these unstable carbon nuclei can emit a little extra energy in the form of gamma rays and become the stuff of life, stable carbon-12.
A research article recently published online by the journal Nature Communication describes the researchers’ supercomputer simulations and the resulting theory of the nuclear structure of carbon that promotes its formation in the cosmos. The corresponding author is Takaharu Otsuka from the University of Tokyo, the RIKEN Nishina Center for Accelerator-Based Science and the Advanced Science Research Center of the Japan Atomic Energy Agency.
The article describes how alpha particles – atoms of helium-4, with two protons and two neutrons – can group together to form much heavier atoms, including an unstable, excited state of carbon-12 known as Hoyle’s state (predicted by theoretical astrophysicist Fred Hoyle in 1953). precursor of life as we know it).
The researchers write that this clustering of alpha particles “is a very beautiful and fascinating idea and is indeed plausible because the (alpha) particle is particularly stable with a large binding energy.”
To test the theory, the researchers performed supercomputer simulations, including calculations on the Fugaku supercomputer at the RIKEN Center for Computational Science in Kobe, Japan. Fugaku is listed as the most powerful supercomputer in the world and is three times more powerful than No. 2, according to the latest TOP500 supercomputer rankings.
Vary said the researchers also did their work ab initio, or from first principles, meaning their calculations were based on known science and did not include additional assumptions or parameters.
They also developed statistical learning techniques, a branch of computational artificial intelligence, to reveal the alpha clustering of the Hoyle state and the eventual production of stable carbon-12.
Vary said the team has worked for more than a decade developing its software, refining its supercomputer codes, performing its calculations and solving smaller problems while expanding the current work.
“There’s a lot of subtlety — a lot of beautiful interactions going on in there,” Vary said.
All calculations, physical quantities and theoretical subtlety match the experimental data available in this corner of nuclear physics, the researchers wrote.
So they believe they have basic answers about the origins of carbon-12. Vary said this should lead to more studies looking for “fine details” about the process and how it works.
Was carbon production, for example, primarily the result of internal processes in stars? Vary requested. Or was it supernova star explosions? Or super dense neutron star collisions?
One thing is now clear to the researchers: “This nucleosynthesis in extreme environments produces a lot of stuff,” Vary said, “including carbon.”
Reference: “α-Clustering in Atomic Nuclei from First Principles with Statistical Learning and Hoyle’s State Character” by T. Otsuka, T. Abe, T. Yoshida, Y. Tsunoda, N. Shimizu , N. Itagaki, Y. Utsuno, J. Vary, P. Maris and H. Ueno, April 27, 2022, Nature Communication.
In addition to James Vary and Pieter Maris from Iowa State University and Takaharu Otsuka from the University of Tokyo, the research team includes:
- Takashi Abe of the RIKEN Nishina Center for Accelerator-Based Science and the Center for Nuclear Study at the University of Tokyo
- Tooru Yoshida of the University of Tokyo Center for Nuclear Studies and the Information Science and Technology Research Organization
- Yusuke Tsunoda of the University of Tokyo Center for Nuclear Studies
- Noritaka Shimizu of the University of Tokyo Center for Nuclear Studies
- Naoyuki Itagaki of the Yukawa Institute of Theoretical Physics of Kyoto University
- Yutaka Utsuno of the Center for Advanced Scientific Research of the Japan Atomic Energy Agency and the Center for Nuclear Studies of the University of Tokyo
- And Hideki Ueno from the RIKEN Nishina Center for Accelerator-Based Science