spectral-class

spectral type

noun Astronomy.
a category for classifying a star, as A star or G star, according to features of its spectrum, as its shape as a function of temperature and wavelength and its absorption spectrum, that indicate the surface temperature of the star and the presence of particular atoms or molecules in its outer layers: principal types are spectral types O, B, A, F, G, K, and M.
Also called spectral class.


Origin:
1920–25

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Collins
World English Dictionary
spectral type or spectral class
 
n
any of various groups into which stars are classified according to characteristic spectral lines and bands. The most important classification (Harvard classification) has a series of classes O, B, A, F, G, K, M, the series also being a scale of diminishing surface temperature
 
spectral class or spectral class
 
n

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American Heritage
Science Dictionary
spectral type  
A classification system for stars based on the strength of their spectral lines, using the letters O, B, A, F, G, K, M, L, and T to denote a range from blue (as in blue giant stars) to dim red (as in brown dwarfs). The spectrum of a star correlates with its surface temperature, ranging from over 60,000°K (O type) to less than 3,500°K (L and T types). See also Hertzsprung-Russell diagram.
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