Neutrinos are produced by fusion reactions in the Sun, passing effortlessly through its dense interior. Different reactions produce neutrinos with different energies, and researchers think this could be a way they could probe the interior of the Sun. Various Earth-based solar neutrino observatories are catching neutrinos hurled by the Sun, which can be compared to those produced by nuclear reactors. This will allow astronomers to build up an interior map of the Sun.