In one of the latest issues of the Nature magazine, the international Borexino Collaboration – which includes Prof. Marcin Wójcik and Dr Grzegorz Zuzel from the JU Institute of Physics – has informed us of the first direct observation of the solar pp neutrinos.

"In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun's energy and contributing to the discovery of neutrino oscillations, those from proton–proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrinos, demonstrating that about 99 per cent of the power of the Sun, 3.84 × 10³³ ergs per second, is generated by the proton–proton fusion process" – taken from the abstract available at Nature's website.

Borexino is one of the most sensitive detectors in the world and the only one which can register low energy solar neutrinos in real-time. Its detector is a high-purity liquid scintillator calorimeter, in which the number of radioisotopes is over 11 orders of magnitude lower than in, for instance, demineralised water. The detector has been installed in the Gran Sasso underground laboratory (LNGS) in Italy in 2007. Since then, it has provided us with information concerning practically every solar neutrino type as well as the "geo-neutrinos." These are neutrinos that are formed from the decay of radioactive isotopes present in Earth.

For more information, visit the Borexino Official Website or the website of the Experimental Computer Physics Department.

Other useful links:

• "Scientifc American",
• "Astronomy",
• "Spektrum" (in German),
• "New Scientist",
• "Physics World".