In a technical tour de force, physicists have spotted long-sought low-energy neutrinos zipping from the sun. The discovery confirms one of the first possible steps in the fusion cycle that helps power the star, says Cristiano Galbiati, a physicist at Princeton University and member of the large international team that reports the discovery in the Feb. 3 Physical Review Letters.
The newfound particles are produced when two protons and an electron interact to make deuterium, a heavy form of hydrogen that helps feed the sun’s fusion. About 1 in 400 deuterium atoms in the sun are made in this proton-electron-proton, or pep, reaction.
Scientists can probe the sun’s inner workings by studying the particles produced in its thermonuclear reactions — in particular, the neutrinos that flood through Earth in great numbers but hardly interact with matter here. Researchers must build detectors underground to screen out these elusive solar neutrinos from other particle chatter.
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