Stars have to be a certain size to initiate fusion to begin with, correct?
Isn't this why brown dwarfs are considered 'failed stars'?
But wouldn't the Sun (and other stars with sufficient mass, like even the smallest red dwarf) achieve much or even most of its heat, energy and light production simply via the crashing and smashing together of particles?
After all, a star must be at least four million Kelvin in its core to initiate sustained fusion, right?
What percentage of the Sun's total energy release is simply from its blackbody temperature that it would have due to size alone without radioactive decay or fusion?
P.S.: If the smallest Red Dwarf must be at least about 4,000,000 Kelvin to initiate fusion, near the beginning of its life, how hot would the Sun have gotten? About 5 or 6 million K? Without any fusion/decay energy?