Astronomical spectroscopy is the technique of spectroscopy used in astronomy. The object of study is the spectrum of electromagnetic radiation, including visible light, which radiates from stars and other celestial objects. Spectroscopy can be used to derive many properties of distant stars and galaxies, such as their chemical composition, but also their motion by Doppler shift measurements.

Stars

Astronomical spectroscopy began with Isaac Newton's initial observations of the light of the Sun, dispersed by a prism. He saw a rainbow of colour, and may even have seen absorption lines. These dark bands which appear throughout the solar spectrum were first described in detail by Joseph von Fraunhofer. Most stellar spectra share these two dominant features of the Sun's spectrum: emission at all wavelengths across the optical spectrum (the continuum) with many discrete absorption lines, resulting from gaps of radiation.

Fraunhofer's original (1817) designations of absorption lines in the solar spectrum