spectral type

American  

noun

Astronomy.

1. 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.

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spectral type British  

noun

1. 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

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spectral type Scientific  

1. 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).

2. See also Hertzsprung-Russell diagram

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Etymology

Origin of spectral type

First recorded in 1920–25

Example Sentences

The visible star in this binary system is spectral type O. Measurements of the Doppler shifts of the O star’s spectral lines show that it has an unseen companion.

From Textbooks • Oct. 13, 2016

Note also that several of the stars in Appendix J are spectral type B, a type that is completely missing from Table 18.1.

From Textbooks • Oct. 13, 2016

Since brown dwarfs cool steadily throughout their lifetimes, the spectral type of a given brown dwarf changes with time over a billion years or more from late M through L, T, and Y spectral types.

From Textbooks • Oct. 13, 2016

To seek the Milky Way’s farthest-flung residents Bochanski's team started with nearly seven million stars, using near-infrared data to select those whose colors match spectral type M, which designates stars that are cool and red.

From Scientific American • Aug. 11, 2014

Morey set to work at once with the telescope; trying to find the nearest star of spectral type G-0, as had been agreed upon.

From Islands of Space by Campbell, John Wood