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The spectral type is not a numerical quantity, but the sequence of spectral types is a monotonic series that reflects the stellar surface temperature. Modern observational versions of the chart replace spectral type by a color index (in diagrams made in the middle of the 20th Century, most often the B-V color) of the stars.
A simple chart for classifying the main star types using Harvard classification. In astronomy, stellar classification is the classification of stars based on their spectral characteristics.
The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts ...
The MK classification assigned each star a spectral type—based on the Harvard classification—and a luminosity class. The Harvard classification had been developed by assigning a different letter to each star based on the strength of the hydrogen spectral line before the relationship between spectra and temperature was known.
A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. [1] B-type stars are extremely luminous and blue.
This was based on the relative strengths of certain spectral lines understood to be sensitive to the luminosity of a star. [47] In the Bright Star Catalogue 5th edition it is given the spectral class F0II, the luminosity class indicating a bright giant. [48] Balmer line profiles and oxygen line strengths indicate the size and luminosity of ...
In 1943, β Ursae Majoris was listed as a spectral standard for the class of A1 V. [11] When improved instruments made it possible to identify subgiant luminosity classes for early A-class stars, β Ursae Majoris was assigned that class A0 IV. [12] This was later revised to A1 IV. [3]
It is an ageing A-type star of spectral class A0 III [7] located 280 ± 20 light-years away [8] from the Solar System. At the age of 385 million years, [9] it is exhausting hydrogen at its core and leaving the main sequence. γ Sextantis is the second brightest star in the constellation with an apparent magnitude of 5.05.