1. How do astronomers know what the outer layers of the Sun are made of? a. we send graduate students there to get samples b. several spacecraft with good shielding have approached the Sun and obtained samples c. the surface layers of Mercury have been laid down by the Sun and are thus made of the same material as the Sun d. the Sun's wind gives us an accurate measure of all the different elements in the Sun e. we take an absorption line spectrum of the Sun, and the absorption lines tell us what elements are present in the outer layers