A neutrino is a sub atom ic particle with no electric charge . Neutrinos are known for their ability to propagate over considerable distances through solid matter almost unaffected. Neutrinos were originally thought to have no mass . Today they are believed to have mass, but it is exceedingly small, only a tiny fraction of the mass of a proton .
Three types of neutrinos, called flavors, are currently known. One type is related to the electron . Another type is related to a particle called the muon . The third type is related to a particle called the tau . The main difference between the neutrinos and their "relatives" is the fact that neutrinos are electrically neutral, while the electron, muon, and tau are electrically charged.
Neutrinos are emitted in huge numbers by stars, including the sun. They are important to astronomers and cosmologists, because their behavior provides clues to the evolution of stars and galaxies. Neutrinos may give insights into how the universe was formed, how large it is, and what will ultimately happen to it.
Neutrinos are difficult to detect, because they do not readily interact with other forms of matter. But using special equipment located in deep underground laboratories where no other cosmic particles can penetrate, scientists have detected neutrinos and discovered some of their properties.