Milky Way as seen by the human eye: where exactly do those photons come from? I'm asking here about the diffuse glow seen by the human eye, when looking at the Milky Way.

Where do those visible photons come from exactly?


the surface of a star?
starlight bouncing off something (dust or a molecule)?
emitted by gas in the interstellar medium?
all of the above?
I believe that the answer is mainly the first (directly from stars), although there will certainly be some of each of the others. The diffuseness comes from the fact that there are many more relatively dim stars than rods in the retina of the human eye.  My argument for this is that magnified photographs of most of the Milky Way at least, break down into individiual stars, as seen in this image from astropixels.com