Stellar Classes - Introduction
The image to the right shows a comparison of stars from each class that are on the main sequence. Click to enlarge.
||Main Sequence/Dwarf Stars
Astronomy & Cosmology
Stars - Stellar Classes
Stars are divided up into a series of classes (types O, B, A, F, G, K, M. Remember as "Oh Be A Fine Girl, Kiss Me), as shown in the table on the right. It is known as the Morgan-Keenan system. This classification is based on their spectral characteristics; essentially indicating the temperature of the chromosphere. There are further subdivisions within each class, indicated by a number from 0 to 9 so that a G2 star, like our sun for example, is two-tenths of the way between G0 and K0. There are various extensions to this, some of which are shown in the lower part of the table, below the main classes; Variables, Carbon Stars etc. The following pages are structured as the table from Type "O" down to Carbon Stars, with more information about stars of each type as well as some examples.
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T & Y
An additional element is the luminosity which gives a reasonable indication of a star's size. This is shown by the numerals 0 through VII as shown in the second table to the near right. The Sun is a luminosity V star, so its full classification is type G2V. In fact, the luminosity scale is further subdivided, and you can find the complete luminosity scale here.