Correct me on any incorrect assumptions!
It’s my understanding that the best guess of the age of the Universe is around 15 billion years old.
It is also my understanding that new stars/planet systems formed from the leftovers of old stars. I am assuming (actually, I think I recall reading somewhere in my youth) that this is where heavier elements come from… leftovers from Stars.
So, if the Earth and our Sol system is around 5 billion years old, is it a safe assumption that there has been roughly 3 generations of stars since the Big-Bang?
Are any of the original stars that were first formed around the big bang still around or are they all long gone? Can a star last for the say, 15 billion years since the beginning of time? Or, did the universe have to “cool” for a few billion years after the BB before stars could even form in the first place?