The world's first neutrino observation in a hydrogen bubble chamber. It was found Nov. 13, 1970, in this photograph from the Zero Gradient Synchrotron's 12-foot bubble chamber. The invisible neutrino strikes a proton where three particle tracks originate (lower right). The neutrino turns into a mu-meson, the long center track (extending up and left). The short track is the proton. The third track (extending down and left) is a pi-meson created by the collision.
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Argonne National Laboratory

Neutrinos

The neutrino is an extremely light (and possibly massless) neutral particle. The neutrino belongs to the family of leptons, the particles that interact through the so-called weak force. For this reason and because it is electrically neutral, neutrino interactions with matter are extremely rare.

Fusion reactions in the Sun produce neutrinos through a process known as beta decay. By detecting these neutrinos, scientists can learn about the solar interior. Because neutrinos do not interact with matter, they are very difficult to detect. The Sun is estimated to produce some 1038 neutrinos per second. Billions of these neutrinos pass through the Earth without a single interaction. Large and very sensitive detectors are actually able to detect neutrinos.

Click here for a brief history of the discovery of neutrinos.

Neutrinos are produced in a variety of nuclear processes: most of the neutrinos that reach Earth from space come from the Sun (solar neutrinos). Other sources of neutrinos are the Earth's atmosphere (neutrinos are produced in reactions triggered by cosmic gamma rays), exploding stars (supernovae), relic neutrinos (according to the current theory about the origin of the universe) and nuclear power plants.


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