Hey PF, Since there are stars that can be powered predominantly (>50%) by the CNO cycle, which requires carbon as a catalyst, and i understand the core temperatures of these stars is about 106 K. Does this mean that stars where the triple-alpha process is dominant (108 K) had to exist and die previously for there to be enough carbon available to dominantly CNO power a star. I'd say the bigger question attached to this is "Is there a limit to the earliest period where it is possible for stars to exist powered more than 50% by the CNO cycle?" and maybe to go a step further "alternatively, does this mean that regardless of the over density regions in the primordial times, where it would be more likely for a hot star to form, (correct me if i've misunderstood the consequences of over and underdensity regions) that there still couldn't be dominantly CNO powered stars (occupying a region around 106K) until enough hotter stars existed to generate enough carbon for the cooler stars to exist?" I feel like i'm missing something blatantly obvious here? Possibly, I've made the assumption that i am ignorant of either an early universe carbon nucleosynthesis event, or just that i am not appreciating the abundance of carbon generated by supernova nucleosynthesis and rare fusion events in some stars.