I am not an astrophysicist (or a physicist even) but one piece of evidence that may be useful here: Based on our understanding of the nuclear fusion reactions,

I am not an astrophysicist (or a physicist even) but one piece of evidence that may be useful here: Based on our understanding of the nuclear fusion reactions, starting from hydrogen, we expect to see, for a star of a given light / radiation spectrum (viz. Young stars, old, white dwarfs, super giants, etc ), emit spectra lines indicative of different elements such as H, He, O, C, etc. [1]. Young stars may not have all the "heavier elements", older stars do. Their relative abundance also changes with age. Our models & predictions of stellar nuclear fusion (afaik) correspond very well with the specific emission spectra we detect for different star types. Which also corresponds very well to the size / lifetime of star, etc. So, the data is very very consistent with nuclear fusion happening in stars. Now, it may be possible that they are just the "other ends" of white holes. But if it were so, then the model becomes far mode complex, plus, where are all the black holes? While I do not know if the total number / mass of all extant blackholes is as much as the total stellar mass, I would suspect it's far far lesser. Probably wouldn't add up. This is just the first explanation that came to my mind. I am certain there are others. Again, this is a non-physicist's lay analysis. Take it FWIW. :) [1] https://en.m.wikipedia.org/wiki/Astronomical_spectroscopy https://en.m.wikipedia.org/wiki/Astronomical_spectroscopy