Scientists from the Jagiellonian University Institute of Physics working on the BOREXINO experiment, realised in an underground laboratory in San Grasso (Italy) together with European and US researchers, have finally found the missing link in the chain of hydrogen burning in the Sun, for the first time in history measuring a weak carbon, nitrogen and oxygen (CNO) neutrino stream emitted from the star’s core.
According to the well-established hypothesis proposed by Hans Bethe in 1939, the Sun produces energy by burning hydrogen and transforming it into helium. When 4 protons are combined to form a helium nucleus, it results in the release of 2 electrons, 2 neutrinos (the lightest known elementary particles) and a massive amount of energy. The reaction can occur in one of two ways: the p-p cycle and the CNO cycle.
The BOREXINO detector has already provided extensive information on the fundamental p-p cycle which accounts for 99% of the Sun’s total energy output. The only thing that remained undiscovered was the CNO cycle, which, although is relatively insignificant in the case of our Sun, may still prove to be the dominant one in case of much larger stars; therefore, registering it would certainly be vital in investigating other celestial bodies.
By using one detector with an unprecedented sensitivity and quality, researchers were able to fully confirm the source of Sun’s energy, effectively identifying two distinct cycles: a veritable milestone in the 25-year-long experiment which is set to end next year.