I just finished talking about the Sun. I will now generalize some of the things that I talked about to Main Sequence stars in general. Note that the theoretical definition of a Main Sequence star is a star which is undergoing hydrogen burning in its core. It turns out that most stars that we see in the Universe are in this stage of their evolution.
But, before moving on, let me remind you that the principal factor which determines how a star evolves is its mass. This is codified in the so-called Russell-Vogt Theorem.
Now let me address:
The rather amazing thing is that the above can be deduced from purely theoretical arguments and that based on theoretical calculations, the principal properties of Main Sequence stars can be explained.
