Spectral Data for Stars (SQA National 5 Physics): Revision Note

Spectral data for stars

• When astronomers study the spectra of stars, they observe the same dark lines as seen in the absorption spectra of known elements on Earth

• This is because the white light produced by a star passes through gases in its outer layers

• As it does so, specific wavelengths of the white light are absorbed

Determining the chemical composition of the Sun

The dark lines on the absorption spectrum of the Sun tell us about its chemical composition, which is that it contains hydrogen, helium and sodium, but not calcium or mercury

• By comparing the absorption spectra of a star to the spectra of known elements here on Earth, astronomers can determine the chemical composition of the star

• For example, the absorption spectrum of the Sun tells us that it is predominantly made of hydrogen and helium gas