What are neutrinos?
Neutrinos are subatomic particles produced by the decay of radioactive elements and elementary particles that lack an electric charge. They’re so tiny that they can pass through solid matter without colliding with any molecules and they travel at close to the speed of light, making them incredible intergalactic messengers. Ordinary matter is made of neutrons, protons, electrons and neutrinos. Neutrinos are emitted when neutrons transform into protons in nuclear reactions. They are produced in the nuclear reactions in the sun and in those ignited by the collapse of a dying star. Besides the particles of light they are the most common particle in the universe; they are much more numerous than protons and neutrons. IceCube detects the blue light emitted by the nuclear reaction of a single neutrino crashing into an ice atom. Neutrinos are attractive for high-energy astronomy because they are not absorbed in dense sources like other probe particles, and they travel in straight lines from th
. A neutrino may belong to any one of the three families, making it an electron-neutrino, or a mu-neutrino, or a tau-neutrino. Or, it may be a superposition of the three family flavors, mixed in some proportions. Now, the standard model assumes that the neutrinos emitted from the sun are in a pure electron-neutrino state, with no mixing. If this assumption is wrong, however, interesting things may happen en route.
