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Astronomical spectroscopyAstronomical spectroscopy is the technique of spectroscopy used in astronomy. While spectroscopy is described in its own article, this article focuses on its use in astronomy. The object of study is spectrum of electromagnetic radiation, which radiates from stars and other celestial objects.
Stellar spectroscopy proved immediately useful in that it allowed scientists to figure out the composition of stars. The current stellar classification scheme originally referred to the strength of the hydrogen lines with A being the strongest. It was only later than a connection with temperature was found.
It was also responsible for the discovery of helium which was discovered in solar spectrum before being discovered on earth. What causes the lines in stellar spectrum remained a mystery until the end of the 19th century and the discovery of quantum mechanics.
Today, the spectra of main sequence stars is considered to be largely understood, and stellar spectroscopy is used as a tool to derive other quantities. For example, the spectra of a star can be used to derive the absolute magnitude of a star which can then be used to derive its distance. Stellar spectrum can also be used to derive the age of a star in that recently formed stars have a far higher concentration of elements heavier than helium than stars that were formed early in the universe.
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