Question: What are stars made of?

Susan Cartwright answered on 19 Jun 2015:

The surface composition of all stars is about the same: roughly 3/4 hydrogen and 1/4 helium by mass. The amount of heavier elements varies, but is always small: in the Sun all the elements heavier than helium together make up only 2% of the Sun’s mass, and in many stars it’s more like 0.002%.

Inside the Sun, there is relatively more helium and less hydrogen, because the Sun is powered by converting hydrogen to helium. Inside very massive stars close to the end of their lives, there will be layers of successively heavier elements: hydrogen at the surface, then helium, carbon, oxygen, magnesium and so on down to iron in the centre – a star with an iron core has literally a few days to live before it explodes.

White dwarfs, which are the dead remains of stars like the Sun, have used up or lost all their hydrogen and helium, and are made of carbon with some oxygen.