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Science Frontiers ONLINE No. 46: Jul-Aug 1986 |
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Solar Neutrino Update
Our terrestrial neutrino detectors catch only about 1/3 as many solar neutrinos as stellar theory requires. We frequently refer to this anomaly because at risk here is our basic theory of how stars work. Is our knowledge of stellar furnaces fundamentally in error or are some of the solar neutrinos somehow removed from the stream of neutrinos bound for earth?
Recent calculations by Hans Bethe have brought sighs of relief to all astrophysicists. Without going into all of the details, Bethe finds that the interactions of the electron-neutrinos emitted by solar thermonuclear reactions with atoms constituting the solar mass change a substantial fraction of them into muonneutrinos. Since our terrestrial neutrino detectors register only electron-neutrinos, we may really be seeing only a fraction of the total number of neutrinos being emitted by the sun. If Bethe's calculations turn out to be correct, he may have eliminated a Class1 anomaly. But at a price! It seems that his calculations also predict a mass of only 0.008 electron-volts for the muon-neutrino. This is much too small for neutrinos to account for the "missing mass" of the universe -- something cosmologists had devoutly hoped for.
(Maddox, John; "Hans Bethe on Solar Neutrinos," Nature, 320:677, 1986.)