The long-sought particles involved in the sun's thermonuclear reactions are giving scientists insights to its inner workings, said Princeton University physicist Cristiano Galbiati, a member of the international team behind the neutrinos' detection.
They are produced when two protons and an electron come together to make deuterium, a heavy form of hydrogen acting as fuel for the fusion process. Only about one in 400 of the sun's deturium atoms are formed in this so-called pep reaction, with the rest involving a high-energy proton-proton or pp event.
In 2007, a project dubbed Borexino started trying to detect these neutrinos streaming from the sun using a giant vat of liquid buried in a mountain in central Italy.
Such detector projects must be deep underground to screen out other particles so they can look for neutrinos that pass through the Earth, only occasionally interacting with the liquid in the detectors.
Scientists were confident they could spot neutrinos from the more common and higher-energy pp, reaction but were not so sure about pep reactions, ScienceNews.org reported.
"We didn't expect to be able to see the pep neutrino when we started," Frank Calaprice, a team member also at Princeton, said. "We knew it might be possible, but there were huge barriers."
The scientists found they could spot the telltale signs of pep neutrinos at the expected energy levels causing visible sparkles when reacting with the liquid in the experiment.
Further studies of pep neutrinos should help scientists fine-tune their understanding of the sun and its processes, physicist Mark Chen of Queen's University in Canada said.