Neutrinos are ghostly particles that hardly ever interact with normal matter. Chargeless, they simply do not interact with the electromagnetic force and thus do not participate in most everyday interactions.

However, they do play an important role in nuclear reactions, since neutrinos do interact via the weak nuclear force. The fusion reaction chain that merges hydrogen into helium in the core of the sun naturally produces neutrinos as a byproduct, and sensitive detectors (ones capable of observing an incredibly rare weak-force scattering event as trillions of neutrinos pass seamlessly through the apparatus) can thus be used to probe the nuclear heart of our nearest star.

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Just like there are different generations (or kinds) of electron-like particles differing only by mass — including the familiar electron, the muon and the tau particle, plus their associated antiparticles — there are different generations of neutrinos, one each paired to the electron, muon and tau. It is currently suspected that neutrinos are their own antiparticles, but that has not been conclusively determined.

Interestingly, neutrinos kinds aren’t fixed as they propagate through space. What starts off as an electron-neutrino can transmute into a muon-neutrino or tau-neutrino en route, before cycling back. 

"We Don't Planet" is hosted by Ohio State University astrophysicist and COSI chief scientist Paul Sutterwith undergraduate student Anna Voelker. Produced by Doug Dangler, ASC Technology Services. Supported by The Ohio State University Department of Astronomyand Center for Cosmology and AstroParticle Physics. You can follow Paul on Twitterand Facebook.