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O type main sequence star series#

It was only much later that it was discovered that the strength of the hydrogen line was connected with the surface temperature of the star. Later it was found that some of the classes were actually duplicates and those classes were removed. Other lines of neutral and ionized species then came into play (H and K lines of calcium, sodium D lines, etc).

O type main sequence star series#

When people first started taking spectra of stars, they noticed that stars had very different hydrogen spectral lines strengths, and so they classified stars based on the strength of the hydrogen Balmer series lines from A (strongest) to Q (weakest). The reason for the odd arrangement of letters is historical. The Hertzsprung-Russell diagram relates stellar classification with absolute magnitude, luminosity, and surface temperature. A popular mnemonic for remembering the order is " Oh Be A Fine Girl/Guy, Kiss Me" (there are many variants of this mnemonic). The mass, radius, and luminosity listed for each class are appropriate only for stars on the main sequence portion of their lives and so are not appropriate for red giants. The common classes are normally listed from hottest to coldest (with mass, radius and luminosity compared to the Sun) and are given in the following table. Harvard one-dimensional (temperature) classification scheme (based on hydrogen Balmer line strengths) was developed at Harvard College Observatory in about 1912 by Annie Jump Cannon and Edward C. In the late 1890s, this classification was superseded by the Harvard classification, which is discussed in the remainder of this article.

Class V: emission lines (e.g., Be, Bf, etc.).

Class IV: red stars with significant carbon bands and lines ( carbon stars).

Class III: orange to red stars with complex band spectra (modern class M).

Class II: yellow stars-hydrogen less strong, but evident metallic lines (modern classes G and K).

Class I: white and blue stars with broad heavy hydrogen lines (modern class A).

By 1868, he had developed four classes of stars:

5.5 Non-stellar spectral types: Class P & Qĭuring the 1860s and 1870s, pioneering stellar spectroscopist Father Angelo Secchi created the Secchi classes in order to classify observed spectra.

5.3.3 Classes MS and SC: intermediary carbon related classes.5.3 Carbon related late giant star classes.5.1.2 Classes OC, ON, BC, BN: Wolf-Rayet related O and B stars.