Question

What do astronomers mean when they say that we are all made of star stuff?

Answer 1

Modern science says universe started from Big bang.

Explanation:

Immediately after big ban there was only hydrogen and helium in the universe..Other elements were made by fusion reactions in side stars..More heavier elements were made in supernovas.
we are made of many elements. calcium in our bones. iron in our blood all were made in the fusion reactions inside stars.![enter image source here The great Astronomer late Carl Sagan used to Say we are star stuff.