What ways can we observationally probe what is happening inside of stars as they evolve off the main sequence and thereby directly test the predictions of stellar evolution theory?
1 Answer
We do not need to look at the stars to understand what is happening inside it.
Explanation:
Let's take an example of the sun. The sun is quite simply a giant nuclear fusion reactor. A combination of chemistry and physics gives us the answers we need for the sun and most stars. We do not yet understand pulsars, neutron stars and a few others. By knowing the mass of the sun we know both its history and its future. That's how we can observe what's happening inside the stars.
