ous ▁detection ▁of ▁solar ▁neut r inos ▁was ▁provided ▁by ▁the ▁K ami ok ande - II ▁experiment , ▁a ▁water ▁C eren kov ▁det ector ▁with ▁a ▁low ▁enough ▁energy ▁threshold ▁to ▁detect ▁neut r inos ▁through ▁neut r ino - elect ron ▁el astic ▁scatter ing . ▁In ▁the ▁el astic ▁scatter ing ▁interaction ▁the ▁electrons ▁coming ▁out ▁of ▁the ▁point ▁of ▁reaction ▁strongly ▁point ▁in ▁the ▁direction ▁that ▁the ▁neut r ino ▁was ▁trav elling , ▁away ▁from ▁the ▁Sun . ▁This ▁ability ▁to ▁" point ▁back " ▁at ▁the ▁Sun ▁was ▁the ▁first ▁conclus ive ▁evidence ▁that ▁the ▁Sun ▁is ▁power ed ▁by ▁nuclear ▁interactions ▁in ▁the ▁core . ▁While ▁the ▁neut r inos ▁observed ▁in ▁K ami ok ande - II ▁were ▁clearly ▁from ▁the ▁Sun , ▁the ▁rate ▁of ▁neut r ino ▁interactions ▁was ▁again ▁suppress ed ▁compared ▁to ▁theory ▁at ▁the ▁time . ▁Even ▁worse , ▁the ▁K ami ok ande - II ▁experiment ▁measured ▁about ▁ 1 / 2 ▁the ▁predicted ▁flux , ▁rather ▁than ▁the ▁ch lor ine ▁experiment ' s ▁ 1 / 3 . ▁ ▁The ▁solution ▁to ▁the ▁solar ▁neut r ino ▁problem ▁was ▁finally ▁experiment ally ▁determined ▁by ▁the ▁Sud bury ▁Ne ut r ino ▁Observ atory ▁( S NO ). ▁The ▁radio chem ical ▁experiments ▁were ▁only ▁sensitive ▁to ▁electron ▁neut r inos , ▁and ▁the ▁signal ▁in ▁the ▁water ▁C eren kov ▁experiments ▁was ▁domin ated ▁by ▁the ▁electron ▁neut r ino ▁signal . ▁The ▁S NO ▁experiment