 This was confirmed when the total flux of solar neutrinos of all types was measured and it agreed with the earlier predictions of the expected flux of only electron neutrinos, as seen by Sudbury Neutrino Observatory.The fact that the electron neutrinos could spontaneously change in flight through empty space also confirmed that neutrinos must have mass.Solar models additionally predict the location within the Sun's core where solar neutrinos should originate from, depending on the nuclear fusion reaction which leads to their production.