Table 796 

 RUSSELL DIAGRAM 



621 



Absolute magnitudes (ordinates) of 3,915 stars of different spectrum types (abscissae) 

 determined by the spectroscopic method by Dr. W. S. Adams and his associates. (Courtesy 



of Mt. Wilson Obser- 

 vatory, 1932.) The 

 diagram shows the di- 

 vision of types G, and 

 later, into giants (high 

 luminosity stars) and 

 dwarfs (low luminos- 

 ity) with few or no 

 intermediate stars. It 

 resembles an inverted 

 7, and with the addi- 

 tion of much new ma- 

 terial confirms fully 

 that first drawn by 

 Russell in 1913. 



The stars may be 

 divided into dwarfs, 

 giants and super- 

 giants. In each class 

 the absolute magni- 

 tude progresses nearly 

 linearly with spectral 

 type except for the 

 coolest stars ; the di- 

 rection of change is 

 opposite for the dwarfs 

 from that for the 

 giants and super- 

 giants. The luminosity 

 of the dwarfs decreases 

 regularly with advanc- 

 ing type (reduced sur- 

 face temperature) ; it 

 drops abruptly for the 

 coolest. Among the 

 giants and probably 

 the supergiants the 

 luminosity increases 

 with decreasing tem- 

 perature at least as far 

 as the early subdivi- 

 sions of type M. 



The sequence of 

 normal giants, con- 

 spicuous in types G, K, 

 M, is almost missing 

 for F5 and Go, the 

 luminous stars of these 

 latter types being 

 supergiants. If this 

 sequence is present in 

 type A stars, they are 

 intermingled with the 

 dwarf sequence ; the 

 two sequences appear 

 to cross in near type 

 Fo. If so, the more 

 luminous stars of types 



earlier than A should be those of the main dwarf series sequence. The tendency of both 

 giants and dwarfs, especially giants, to group around definite values of absolute magni- 

 tude is remarkable. About 90 per cent of the Ko stars fall within limits of less than 

 one magnitude. The hottest stars extend dwarf sequence up and to the left (Table 797)- 

 The white dwarfs belong to the lower left corner (Table 828), F to A, M 15 —• 

 Smithsonian Tables 



