IFIC researchers recreate a key nuclear reaction to understand the chemical evolution of our galaxy and solar system

A team from the Institute of Corpuscular Physics (IFIC), located at the University of Valencia Science Park, has succeeded in measuring in a CERN laboratory the formation of a key element in the evolution of the chemical composition of heavy elements. An isotope of this element, Lead-204, is produced in red giant stars, responsible for the creation of half of the elements heavier than iron in nature

A team led by the Institute for Corpuscular Physics (IFIC), located at the University of Valencia Science Park, has managed to recreate in a laboratory at CERN in Switzerland a key nuclear reaction to understand the origin and evolution of our galaxy and the solar system. In a paper published in Physical Review Letters they detail how Lead-204, an isotope that explains the evolution of the chemical composition of our galaxy since the first stars were formed, about twelve billion years ago, is formed. The formation of this isotope in red giant stars also allows dating the first solid materials created in the solar system, and is used to date their age.

The amount of Lead-204 (Pb204) produced in red giant stars could not be precisely quantified to date due to the lack of knowledge of a nuclear reaction that occurs in an isotope of the chemical element that precedes it, Thallium-204 (Tl204). This isotope is radioactive and lasts an average of 3.78 years before disintegrating. It is therefore extremely difficult to produce a sample of this material for experimentation.

Now, a research group from IFIC and the Polytechnic University of Catalonia (UPC), thanks to a collaboration with the Paul-Scherrer Institute (PSI) in Switzerland and the Grenoble High Flux Reactor at the Institut Laue-Langevin (ILL) in France, have managed to produce a thallium-204 sample large enough to work with at CERN's n_TOF neutron experimental laboratory in Geneva (Switzerland).

The results obtained have made it possible to quantify precisely, for the first time, the amount of Lead-204 produced in AGB-type red giant stars. This type of star plays a fundamental role in the evolution of the chemical composition of the elements present in our galaxy and solar system, being responsible for the creation of half of the elements heavier than iron in nature

After synthesizing and characterizing this sample, the research team measured for the first time the reaction of a neutron beam on this isotope. They then performed calculations with astrophysics experts in the framework of NuGrid, an international collaboration that develops tools for large-scale nucleosynthesis simulations with applications in nuclear physics.

The results obtained have made it possible to quantify precisely, for the first time, the amount of Lead-204 produced in AGB-type red giant stars. This type of star plays a fundamental role in the evolution of the chemical composition of the elements present in our galaxy and solar system, being responsible for the creation of half of the elements heavier than iron in nature. The life cycle of these stars continuously contributes to the chemical enrichment of galaxies in the universe.

“The result obtained shows an excellent agreement with lead-204 abundances measured in Ivuna-type carbonaceous chondrites (IC), meteorites that preserve the chemical composition of the solar system,” explains César Domingo, a CSIC researcher who leads the study at IFIC. “It would not be necessary to resort to alternative hypotheses of Pb204 nucleosynthesis, such as supernovae or possible fractionation mechanisms that could have occurred in the early solar system,” he points out.

“Although this experiment has been a significant advance, we need new disruptive ideas to be able to access in the laboratory many more nuclei of great interest like this one, but which are produced in explosive stellar environments such as supernovae or binary neutron star systems”, César Domingo, lead researcher of the study at IFIC

“Although this experiment has been a significant advance, we need new disruptive ideas to be able to access in the laboratory many more nuclei of great interest like this one, but which are produced in explosive stellar environments such as supernovae or binary neutron star systems,” concludes the researcher. 

This work contributes to the development of the scientific challenges of the CSIC White Papers, which bring together the scientific challenges of the 21st century articulated on the UN Sustainable Development Goals. This research is framed in volume 9, which aims to understand the fundamental laws of nature, as they are the basis of technology. The challenges of physics are intimately associated with the technological challenges for the design and construction of telescopes, space missions or accelerators, subway and reactor experiments, as well as advances in mathematics and computation.

Moreover, this research has constituted the doctoral thesis work of Adrià Casanovas Hoste, integrated in a project of the national plan coordinated between the Institute of Corpuscular Physics (CSIC-UV) and the Polytechnic University of Catalonia, as well as in the framework of a European project ERC Consolidator (HYMNS).