One of the early problems with the solar nuclear fusion model was that the observed neutrino flux reaching Earth was only one third the theoretical amount.
This was explained by neutrino oscillation where a neutrino could change "flavours" and oscillate between an electron, muon and tau neutrino.
While neutrino oscillation has been observed in solar neutrinos, it has never been observed in experiments..... until now.
http://news.discovery.com/space/ferm...ge-110704.html
Regards
Steven