How do we know what the stars are made of?
Stars are too far away for us to directly analyze their atmospheres. We can, however, learn a lot about their makeup from the light they emit.
Astronomers pass starlight through their telescopes into a spectrometer to separate the light into a spectrum - a rainbow of its component colors.
Each element on the periodic table gives off a unique pattern of colors - like a hidden fingerprint. Astronomers read the color patterns in starlight to determine the elements present in the star.