An experiment led by the IFIC improves the knowledge on formation of heavy elements in the cosmos

These nucleus, that only exist during fractions of seconds and that cannot be found in their natural form in Earth, have a fundamental role in one of the biggest enigmas of modern physics: how are heavier elements than iron formed. The answer, points towards extreme phenomena such as the fusion of stars of neutrons.

It is known that the lightest elements –hydrogen, helium– were formed after the Big Bang. But in order to create bigger elements –silver, gold, uranium– it is necessary to have much bigger and extreme sceneries, such as supernova explosions or the collision between stars of neutrons.

A game changer came in 2017, when the collaborations LIGO and VIRGO detected for the first time gravitational waves resulting for the fusion between two stars of neutrons. When directing their telescopes to the signalled region in the sky, astronomer observed a luminous signal whose behaviour coincided with a theory prediction: the radioactive disintegration of heavy elements recently formed fed that light. In posterior analysis some traces of strontium, yttrium and zirconium were identified. For the first time, it was live observed the synthesis of elements in a cosmic event.

The problem is that many atomic nucleus that participated in these processes don’t exist on Earth and merely last a fragment of a second, so we weren’t able to study them until now.

The team led by the Group of Gamma-ray and Neutron Spectroscopy from IFIC has achieved a significant advance: they have measured, for the first time, fundamental proprieties from 37 really exotic atomic nucleus that make it possible to predict with more precision how these elements heavier than iron are formed, such as yttrium, zirconium, niobium, or molybdenum, with important industrial applications.

The finding combines production capacity of exotic nucleus from the Radioactive Shafts Institution from the RIKEN-Nishina centre, in Japan, with the efficiency of a neutrons detector developed by the Research Group of IFIC and the Universitat Politècnica of Catalonia. Other teams from the Technical University of Darmstadt (Germany) and the Universitat de València collaborate in the nucleosynthesis calculations, the formation of elements.

Up to a 70% more of elements from what it was first thought

The results of the work, recently published in Physical Review Letters, show that the synthesis process and dispersion of heavy elements fed by a neutrinos wind produces the nucleus measured in this work and happens in the brief lapse of time that happens before the system collapses into a dark hole. The use of the new nuclear data shows a significant increment in the production of elements identified in the event of 2017 respect of the previous estimations.

Álvaro Tolosa Delgado, first author of the work and currently researcher of CERN, comments that “there was a previous opinion about the properties of the nucleus that we have studied having a scarce impact in abundancies. This is denied with our work, which points at the necessity of amplifying this type of measures to other nucleus zones”. For his part, José Luis Taín, researcher of the CSIC in the IFIC that leads the experiment, points out: “the evolution of abundance of chemical elements in the universe is really complex, with variety of processes contributing to the final result. Combining astronomic observations, nuclear physics experiments and astrophysics experiments we are closer to resolving the brain teaser”.

References:

A. Tolosa-Delgado, J. L. Tain, M. Reichert, A. Arcones, M. Eichler, B. C. Rasco, N. T. Brewer, K. P. Rykaczewski, R. Yokoyama et al.Impact of Newly Measured𝛽-Delayed Neutron Emitters around 78Ni on Light Element Nucleosynthesis in the Neutrino Wind Following a Neutron Star Merger.Phys. Rev. Lett.134, 172701. DOI:https://doi.org/10.1103/PhysRevLett.134.172701