Spectroscopy
Spectroscopy is the study of objects based on the spectrum of color they emit or absorb. Spectroscopy is an important investigative tool in astronomy where scientists use it to analyze the properties of distant objects. Typically, astronomical spectroscopy uses high-dispersion diffraction gratings to observe spectra at very high spectral resolutions. Helium was first detected by analysis of the spectrum of the sun. Chemical elements can be detected in astronomical objects by emission lines and absorption lines.
The shifting of spectral lines can be used to measure the Doppler shift (red shift or blue shift) of distant objects. The first exoplanets were discovered by analysis of the Doppler shift of the parent star, revealing variations in radial velocity, the star's speed relative to Earth, caused by the planet's gravitational influence.
Read more about this topic: Visible Spectrum