Astronomy Answers: From the Astronomical Dictionary

Astronomy Answers
From the Astronomical Dictionary

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The description of the word you requested from the astronomical dictionary is given below.

the spectral line

spectum = [Latin] to watch

A spectral line is a very narrow range of wavelengths (colors) at which a bright object such as the Sun shines more brightly or less brightly than at neighboring wavelengths. A spectral line in which an object shines less brightly is called an absorption line, and a spectral line in which an object shines more brightly is called an emission line.

Every substance has its own set of spectral lines, so spectral lines give a sort of fingerprint of the associated substance. The strength of a spectral line (how much absorption or emission it has) depends on many things, including the temperature and gas pressure of the material, and sometimes also of the strength of the magnetic field at that location. The exact wavelength or frequency of a spectral line also depends (through the doppler effect) on the speed of the material relative to the observer. Astronomers often use filters to look at one spectral line in turn, to measure the things that the spectral line is sensitive to.