> They have detected subatomic particles called pp neutrinos, they report in the journal Nature.
It takes a bit of background information to understand the significance of this. After all, pp neutrinos are by far the most common neutrinos generated by the Sun, and neutrinos have been detected from the Sun since at least as long ago as 1970, see http://en.wikipedia.org/wiki/Homestake_experiment for example.
But those early neutrino experiments were only detecting high energy neutrionos.
The Homestake experiment in particular was a Chlorine experiment, so were primarily picking up neutrinos from the decay of an isotope of beryllium. Later experiments, the SuperK (Super-Kamiokande in Japan) and the SNO (Sudbury Neutrino Observatory in Ontario Canada) couldn’t detect p-p neutrinos either but only very energetic neutrinos produced by the decay of an isotope of boron. It was SNO measurements that solved the solar neutrino problem.
It takes experiments using for example gallium to detect the massive numbers of neutrons produced by the p-p process, the fusion of two hydrogen nuclei to make on deuterium nucleus.
GALLEX was a gallium-based neutrino detector that operated under the French Alps from 1991 to 1997. This was the first detection of low energy p-p neutrinos from the Sun. GALLEX was detecting p-p neutrinos at the rate of about three neutrinos every four days.
Other neutrino detection devices using gallium have included the Gallium Neutrino Observatory, begun in 1998 and the Russian-American Gallium Experiment SAGE.
The new detector http://en.wikipedia.org/wiki/Borexino also sits under the French Alps. It began recording solar neutrinos in 2007.