Borexino experiment gathers critical data on how stars shine

The Borexino scientific collaboration is an experiment at the Gran Sasso National Laboratories of the Italian National Institute for Nuclear Physics. Researchers on the project on November 25 announced the first-ever detection of neutrinos produced by the sun by the CNO cycle (carbon-nitrogen-oxygen). The project is an experimental result of historical value completing a chapter of physics that started in the 1930s.

Researchers point out the implication for the measurement on the understanding of stellar mechanisms is enormous. The CNO cycle is predominant in stars more massive than the Sun. By obtaining the observation, Borexino has found the experimental evidence of the most dominant channel in the universe for burning hydrogen.

Borexino previously studied the main mechanism of energy production in the sun in detail. The experiment studied the proton-proton chain via the individual detection of all neutrino fluxes originating from the proton-proton chain. Now that it has been able to measure neutrinos produced by the CNO cycle, Borexino has provided the first experimental evidence of the existence of this additional energy generation mechanism.

The result gives experimental confirmation of how stars shine. The experiment result is the cumulation of a three-decade effort that began in 1990 and of more than ten years of discoveries in the physics of the sun, neutrinos, and stars conducted by Borexino. To achieve the results of the experiment, extreme sensitivity was required.

Borexino was built using an onion-like design characterized by layers of increasing radio purity making it the most unique detector in the world for ultra-low background level. The experiment was placed underground to protect it from cosmic radiation except for neutrinos that can pass through Earth undisturbed. Researchers point out that measuring the CNL cycle's neutrinos was complicated and required significant hardware and software effort.