What do the absorption lines tell us about stars?

Absorption lines in a star's spectrum provide crucial information about its chemical composition, temperature, density, and pressure. These lines result from specific wavelengths of light being absorbed by elements and molecules in the star's atmosphere, allowing astronomers to identify the presence of various elements. Additionally, the strength and width of these lines can indicate the star's temperature and surface gravity, revealing insights into its evolutionary stage. Overall, absorption lines serve as a key tool for understanding the physical properties and processes occurring within stars.