1. Chemical Composition: Spectrographs break down starlight into its component wavelengths, creating a unique spectral fingerprint. By analyzing the absorption lines (dark lines) in the spectrum, astronomers can identify the elements present in the star's atmosphere. The strength of the absorption lines tells them the relative abundance of each element.
2. Radial Velocity: The Doppler effect causes the wavelengths of light from an object moving towards us to be shifted towards the blue end of the spectrum (blueshift), while the wavelengths from an object moving away are shifted towards the red end (redshift). By analyzing the shift in the star's spectral lines compared to a reference spectrum, astronomers can determine the star's radial velocity (how fast it's moving towards or away from us). This information can be used to detect planets orbiting the star through the wobble they cause in the star's motion.
