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Solving the Solar Neutrino Mystery
by Dr. Bruce Twarog, University of Kansas

One of the fundamental problems in stellar and solar astronomy for the last 30 years has been the deficiency of the elusive particles called neutrinos emitted by the sun. The discrepancy between theory and observation has produced a wide array of explanations, including claims that our understanding of solar physics was flawed. Due to the convergence of improving technology for analyzing the structure of the sun and for detecting neutrinos, the issue has now been resolved, while opening new avenues for research in particle physics.

According to Dr. Twarog, solving a problem opens up new problems of its own. This is what happened with the Solar Neutrino Mystery.

The standard model of the sun describes the boundary conditions, luminosity, temperature, radius, chemical composition and mass of the solar body. According to the standard model, the sun is at hydrostatic equilibrium that prevents the solar radius from changing. This mean that the mass of the sun collapsing in on itself due to gravitational sources is counterbalanced by the energy generated by the forces generated in the solar interior. In simple terms, the energy in equals the energy out.

Nuclear fusion is the energy source of the sun. The proton-proton chain is the mechanism. Neutrinos are a by-product of nuclear fusion. They are created in the sun, and pass out immediately.

Neutron detectors on Earth are used to measure this neutrino flow from the sun. But not all neutrino detectors are alike. There are different methods to detect neutrino energy, which fall into three categories: the Chlorine Experiment, the Kamio Caldle II Experiments, and the Sage, Gallex Experiment. From experience, scientists have determined that gallium is better than chlorine to detect neutrinos. The most successful of these neutrino experiments is the Sudbury Neutrino Observatory, which consists of a 12-memter sphere of deuterium dioxide.

The findings are that solar fusion always  makes electron neutrinos. But during the time it takes them to move from the core where they are generated to the surface of the sun, they change into other neutrino types. Thus, the electron neutrino ends up accounting for only about one-third of the neutrino types emitted from the sun.

Bruce Twarog received a BS in Astronomy in 1974 from Case Western Reserve University. He did his graduate work at Yale University, receiving an MS in Astronomy in 1978 and a PhD in 1980. After spending two years on the faculty of the Astronomy Department at the University of Texas at Austin, he joined the Department of Physics and Astronomy at the University of Kansas in 1982, where he remains a Professor of Physics and Astronomy. His research interests are concentrated on the evolution of the galaxy as revealed through photometric studies of the stars and star clusters that populate it.

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