Neutrinos could be distinguished by energy, and also from antineutrinos. There would be an upper bound to the energy that could be detected because at some ene

Neutrinos could be distinguished by energy, and also from antineutrinos. There would be an upper bound to the energy that could be detected because at some energy the Sun becomes opaque to neutrinos. Yes, they are hard to detect, so this is a massive project, not practical right now. The last point is why there's a caustic. The focal length diverges to infinity as you get to the center; there's a radius where it's at a minimum. This radius will be well within the sun, since the center of the Sun is so much denser than outside the Sun. The neutrino gravitational focus should be somewhere between the orbits of Uranus and Pluto: https://www.nasa.gov/general/cube-sat-space-flight-test-of-a-neutrino-detector/ https://www.nasa.gov/general/cube-sat-space-flight-test-of-a...