How do astronomers learn about the internal structure and evolution of stars?

How does a new star form?

What causes a supernova to occur? Explain.

Is the lifetime of a massive star shorter or longer than a star like the Sun? Why?

Astronomers learn about the internal structure and evolution of stars by using spectroscopy and observing their luminosity.

New stars form in nebulae, interstellar gases and dust clouds leftover from supernovas.

Supernovas are the results of stars running out of its nuclear fuels.

The lifespan of a massive star is shorter than a star like the Sun because massive stars have very high pressures and temperatures at their cores and therefore burn their nuclear fuels faster. Stars grow larger as they age.