ASTR 170B1 Lecture Notes - Lecture 18: Neutrino, Helioseismology, Gamma Ray
30 Oct 2018
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How do we know that this is the model: radiative diffusion (drunkard"s walk) It"s very dense at the center of the sun, so a photon can"t travel very far before it interacts with a free electron and changes direction and energy. It can also interact with atoms, but at 20 million degrees f, there aren"t very many atoms with electrons still bounded to them: farther out in the sun, the photons can be absorbed and then re-emitted. When it is re-emitted, the new photon(s) are sent out in a random direction. So they fly right through the sun almost as if it is not there: well , if they are so hard to catch, that means they are hard to detect. So the center of the sun is demonstrably behaving as the models advertise: there are many light-element fusion reactions in the core of the sun. Other reactions make neutrinos of different energies and different flavors.
