
A team led by the Institute of Corpuscular Physics (IFIC), mix centre from the Universitat de València (UV) and the Spanish Research Council (CSIC), have achieved to recreate at a laboratory from the CERN in Switzerland a nuclear recreation that is key to comprehended the origin and evolution of our galaxy and the solar system. In a paper published in Physical Review Letters they describe how Lead-204 is formed, an essential isotope to explain the evolution on the chemical make-up of our galaxy since the formation of the first stars, about twelve billion of years ago. The formation of this isotope in the red giant stars has also permitted to date the first solid materials that were created in the solar system, and are used to determine its age.
The quantity of Lead-204 (Pb204) produced in the red giant stars could not be quantified with precision until now due to the ignorance of a nuclear reaction that takes place in an isotope from the chemical element that precedes it, Thallium-204 (Tl204). This isotope is radioactive and lasts an average of 3,78 years to disintegrate. Therefore, it is extremely complicated to produce a sample of this material to experiment on it.
Now, a research group from the Institute of Corpuscular Physics and the Universitat Politècnica de Catalunya (UPC), thanks to the collaboration of the Paul-Scherrer Institute (PSI) in Switzerland and with the High Flux Isotope Reactor of Grenoble at the Institut Laue-Langevin (ILL) in France, they have achieved to produce a sample of the Thallium-204 big enough to work on it in the experimentation laboratory with neutrons n_TOF from the CERN, located in Ginebra (Switzerland).
After synthetizing and characterizing the sample, the research group measured for the first time the reaction of a beam of neutrons over this isotope. Next, they made numbers with astrophysics experts inside the NuGrid, an international collaboration that develops the tools for nucleosynthesis simulations on a broad scale with nuclear physics application.
The results obtained have permitted to precisely quantify, for the first time, the quantity of Lead-204 that is produced i the red giant stars of AGB type. This type of stars has an essential paper on the evolution of the chemical make-up of the present elements in our galaxy and the solar system, being responsible for the creation of half the elements which are heavier than iron in nature. The life circle of these stars constantly contributes to the chemical enrichment of the universe galaxies.
"The result obtained shows an excellent understanding with a great quantity of Lead-204 measured in carbonaceous chondrites of type Ivuna (CI), meteorites that preserve the chemical composition of the solar system", explains César Domingo, researcher from the CSIC that leads the study at the IFIC. "It wouldn’t be necessary to draw on alternative hypothesis of nucleosynthesis of Pb204, like supernovas or possible mechanisms of division that could have happened in our early solar system", specifies Domingo.
"Despite that this experiment means a significant advance, we need new disruptive ideas to be able to access in the laboratory to more nucleus of great interest like this, but that are produced in explosive stellar environments like supernovas or binary star systems of neutrons", finishes the researcher.
What is more, this research meant the work of the doctoral thesis by Adrià Casanovas Hoste, integrated in a national project coordinated between the Institute of Corpuscular Physics and the Universitat Politècnica de Catalunya, as well as inside the European project ERC Consolidator (HYMNS).