Stellar Astronomy: Part 2 – The Composition of Stars

In part 1, we examined how to measure the distance to relatively nearby stars using parallax.  We then showed how astronomers compute the luminosity of a star by comparing its apparent brightness with its distance.  This shows that stars are comparable in brightness to the sun.  But how do we know that stars have the same composition as the sun?  For that matter, how do we know what the sun is made of?